Seduced by Style: How Instagram Fashion Influencers Build Brand Loyalty Through Customer Engagement in Sustainable Consumption

Abstract

This study explores how Instagram fashion influencers build brand loyalty through customer engagement within the framework of sustainable consumption. Grounded in the stimulus–organism–response (SOR) theory, influencer marketing is conceptualized as a stimulus that activates customer engagement (organism), which in turn enhances brand loyalty (response). A cross-sectional survey was conducted with 279 Instagram users in Palestine who actively follow fashion influencers, and the model was tested using partial least squares structural equation modeling (PLS-SEM). The findings confirm that social media influencer marketing (SMIM) significantly improves both engagement and loyalty. Customer engagement was found to be both a partial mediator and a significant moderator, such that highly engaged consumers exhibited stronger loyalty responses—suggesting intensified value alignment and emotional resonance in sustainability contexts. This study extends the prior literature by integrating the creation–consumption–contribution (C–C–C) model into the SOR framework and conceptualizing engagement as both a psychological state and a boundary condition. It contributes to sustainable consumption research by illustrating how participatory digital behaviors can foster ethical brand relationships, particularly in emerging economies. Practically, it offers strategic guidance for fashion brands and influencers to design campaigns that promote co-creation, authenticity, and eco-conscious narratives. It also emphasizes the importance of aligning influencer values with those of sustainability-minded consumers to foster long-term loyalty. By contextualizing the findings within the Palestinian market, the study highlights how cultural factors may shape engagement and sustainability perceptions, paving the way for future cross-cultural investigations.

1. Introduction

The rapid evolution of digital platforms has significantly transformed how consumers engage with brands, particularly within the fashion industry. In this digital age, social media influencer marketing (SMIM) has emerged as a dominant strategy for brands aiming to cultivate emotional connections, foster engagement, and build long-term loyalty among consumers [1,2]. As brands increasingly prioritize sustainable consumption and digital innovation, influencer-driven marketing offers a compelling avenue to drive not only transactional value but also long-term behavioral changes aligned with environmental and ethical values [3]. This is especially critical in the context of fashion, a sector known for both its environmental footprint and its cultural influence, where SMIM can play a transformative role in promoting sustainable choices [4,5].

Central to this shift is the concept of customer engagement (CE), which has evolved into a critical mechanism through which brands deepen their relationships with consumers [6]. Prior research categorizes CE into three key dimensions—cognitive, emotional, and behavioral—all of which are necessary for fostering meaningful consumer–brand interactions [7,8]. In the digital context, these dimensions are often activated through visually compelling and value-driven content shared by influencers, especially on platforms like Instagram. SMIM plays a vital role in stimulating CE and enhancing brand outcomes [9]. When embedded in sustainable messaging, influencer content not only engages consumers but also fosters identification with green values and eco-conscious lifestyles [10,11,12].

SMIM is defined as the strategic use of individuals with substantial followings on platforms such as Instagram, Facebook, and TikTok to promote products or services through personal, often relatable content [13]. These influencers not only amplify brand visibility but also shape consumer attitudes, behaviors, and decision-making [14]. Despite a growing body of research on SMIM’s impact [15], there remains a critical gap in understanding how influencer-driven content translates into brand loyalty through the mechanism of customer engagement, particularly within the context of sustainable consumption [16,17,18]. For the purpose of this study, sustainable consumption is defined as the use of products and services that meet basic needs and improve quality of life while minimizing resource use and environmental degradation [19,20]. In the context of social media, it also includes engaging with, promoting, and being influenced by eco-conscious content, messages, and practices shared by influencers [4,10,21].

Brand loyalty, which refers to a consumer’s enduring preference for a specific brand despite competing alternatives [22], has been shown to be positively influenced by SMIM and CE in the fashion industry [23]. However, its development depends largely on the credibility, relevance, and emotional resonance of the influencer’s content [24,25]. Influencers serve as informational intermediaries, helping consumers make confident, values-driven decisions about their purchases—an essential factor in fostering sustainable consumption [26]. When influencers promote ethically sourced products, slow fashion, or zero-waste lifestyles, they do more than market brands—they model behaviors that support sustainability goals and build trust through value congruence with their audience [10,27].

Despite these insights, the role of customer engagement as both a mediator and a moderator in the relationship between SMIM and brand loyalty has received limited empirical attention [28,29,30,31]. In response, this study examines how fashion brands operating on Instagram in Palestine can leverage SMIM to build brand loyalty by activating customer engagement behaviors that align with sustainability values.

To guide the study, we draw upon the stimulus–organism–response (SOR) theory [32,33], which posits that external stimuli (e.g., influencer content) affect internal cognitive and emotional states (e.g., customer engagement), which in turn shape behavioral responses (e.g., brand loyalty). Under this framework, SMIM acts as the stimulus, customer engagement as the organism, and brand loyalty as the response [25,28,34]. The SOR theory has been increasingly applied in digital marketing to explain consumer responses to online branding efforts [35]. However, this study expands its application by embedding sustainability-related messaging as an integral component of the stimulus, reflecting growing consumer expectations for eco-conscious branding in digital environments [36,37,38]. Few studies have leveraged this framework to investigate the dual role of customer engagement in the influencer–loyalty relationship, especially in the sustainable fashion consumption context [39,40]. Given these gaps, the present study aims to advance theoretical and practical understanding by addressing four key research questions:

(a)

What is the nature of the relationship between customer engagement and brand loyalty?

(b)

What is the nature of the association between SMIM and brand loyalty?

(c)

Does customer engagement mediate the relationship between SMIM and brand loyalty?

(d)

Does customer engagement moderate the impact of SMIM on brand loyalty?

By exploring these questions within the emerging fashion market in Palestine, this research contributes to the growing discourse on sustainable digital consumption and the strategic role of influencers in shaping consumer behavior and loyalty through meaningful engagement. The regional specificity adds cultural insight, while the sustainability lens expands the implications for influencer marketing in promoting eco-conscious behavior.

2. Theoretical Framework

2.1. Sustainable Consumption

Sustainable consumption has gained prominence as a response to mounting ecological and social concerns associated with overconsumption, waste, and irresponsible production systems [10,41,42]. While early sustainability efforts focused predominantly on supply-side solutions, researchers have emphasized that achieving sustainable development also requires transforming consumer demand patterns [43,44]. Sustainable consumption thus entails the use of goods and services that meet basic needs and improve quality of life while minimizing the depletion of natural resources, environmental degradation, and negative social impacts [19,20]. It encompasses a broad array of conscious decisions that span the entire consumption lifecycle—from product selection and use to disposal and post-use engagement—underscoring the critical role of individual and collective agency in fostering environmental and social well-being.

In this study, sustainable consumption is operationalized as fashion-related consumer behaviors that are informed by environmental, ethical, and social considerations. These include purchasing eco-friendly or ethically produced clothing, engaging with sustainability-oriented content on social media, and participating in practices such as upcycling, thrifting, and supporting slow fashion [4,5]. This perspective aligns with the principles of the circular economy, particularly the reduce–reuse–recycle (3R) model advocated in sustainable development frameworks [21,45]. Moreover, it reflects a shift in consumer identity construction, whereby sustainable consumption is increasingly viewed as a means of signaling values, belonging, and ethical self-concept, especially within digitally mediated environments. By highlighting both purchasing behaviors and digital engagement, this conceptualization broadens the scope of sustainable consumption beyond transactional acts to include value-driven expressions within online platforms.

The fashion industry has traditionally been linked to fast-changing trends, low-cost mass production, and excessive resource use [46,47]. As a result, it has come under scrutiny for its contribution to environmental degradation and labor exploitation. Sustainable fashion—defined as the design, production, and consumption of clothing that minimizes environmental harm and promotes ethical standards—has emerged as a counterforce to fast fashion [48,49]. It is often linked with slow fashion, which prioritizes durability, fair labor practices, and reduced consumption [50]. This evolution in fashion norms has encouraged consumers to reevaluate their purchasing decisions, not only in terms of esthetics and cost but also through the lens of social and ecological accountability.

Despite growing public awareness, sustainable fashion remains underutilized due to consumer skepticism, limited knowledge, price sensitivity, and perceived lack of esthetic appeal [48,51,52]. These barriers highlight the importance of strategic communication and credible advocacy to shift consumption norms—an area where social media influencers are increasingly influential [4,5,27,53]. Given their aspirational status and ability to blend personal storytelling with product endorsement, influencers can reduce perceived barriers to sustainable fashion by making it more desirable, attainable, and socially endorsed.

Social media influencers, especially those active in fashion domains, play a critical role in shaping attitudes toward sustainable consumption. By sharing personal narratives, showcasing sustainable brands, and modeling eco-conscious behaviors, influencers can build trust and foster emotional engagement with sustainability themes [54,55,56]. Their influence is strengthened through parasocial interactions, where followers develop perceived intimacy and authenticity with the influencer [57]. Unlike traditional celebrity endorsements, influencer content is seen as more relatable and trustworthy, enhancing its potential to normalize sustainable behaviors [12,18]. In particular, micro- and nano-influencers—despite their smaller followings—are often perceived as more authentic and accessible, making them powerful agents in driving attitudinal and behavioral change toward sustainability.

Sustainable consumption in the digital era thus transcends economic transactions and encompasses cultural, psychological, and social dimensions. In particular, the convergence of sustainability values and influencer marketing introduces new pathways for promoting responsible fashion consumption, especially among younger generations who are more active on platforms like Instagram [4,11,12,58]. However, this space remains underexplored in the current literature, prompting the need to understand how digital influencers contribute to sustainable fashion engagement and brand loyalty. By addressing this gap, the study also considers the performative nature of digital sustainability, where consumer actions and expressions in online spaces serve not only practical but also symbolic and identity-based functions.

By focusing on the behavioral and communicative aspects of sustainable consumption within the fashion context, this study provides a nuanced lens to examine how Instagram influencers shape consumers’ perceptions, engagement, and loyalty in line with sustainability values. This approach responds directly to recent calls for more integrative research on influencer marketing and sustainability, offering theoretical and practical contributions to digital consumer culture and sustainable branding.

2.2. Social Media Influencers and Sustainable Consumption

In the age of digital transformation, social media has reshaped how consumers access and interact with fashion-related content, with Instagram standing out as the most influential platform in this regard [59]. Fashion brands increasingly rely on SMIM to engage digitally native audiences, particularly among Gen Z and millennial consumers. Influencers share personal narratives, lifestyle visuals, and product endorsements that appear more authentic and relatable than traditional advertisements [4,60,61]. Their content is often perceived as trustworthy due to its perceived credibility, attractiveness, and similarity to followers’ own values, enhancing both brand perception and emotional connection [18,62,63,64,65]. SMIM yields up to eleven times higher returns on investment compared to conventional strategies, demonstrating its effectiveness in shaping consumer decision-making [66]. This makes influencers particularly powerful agents not just of marketing communication but of behavioral influence in broader societal contexts, including sustainability.

Recent research underscores the growing role of SMIM in advancing sustainable consumption—defined as consumer behavior that minimizes environmental harm, supports ethical production, and aligns with long-term ecological goals [10]. As social and environmental concerns rise, many influencers—especially in the fashion domain—have begun integrating eco-conscious values into their content by endorsing sustainable fashion brands, advocating for secondhand clothing, and encouraging mindful consumption habits [4,54]. Such influencers not only raise awareness but also reshape consumption norms by modeling sustainable behaviors in relatable and aspirational ways [67].

Influencer impact on sustainable consumption is largely driven by perceived authenticity and trust. Studies have shown that audiences respond more favorably to influencers than to traditional advertisements due to the emotional bonds they form and the parasocial relationships they develop with them [68,69]. Authenticity—seen in consistent, values-driven messaging—helps build trust, which is critical for influencing complex behavioral domains like sustainability [70]. Moreover, influencers need not be sustainability experts; even fashion influencers without technical expertise can inspire environmentally conscious behavior by embedding eco-friendly tips, messages, or brand collaborations within their regular content streams [71,72].

Although prior studies reveal that influencers have been particularly effective in sustainability domains such as sustainable food [73,74], tourism [75], and fashion [76,77,78], these studies emphasize informational, normative, and minority social influence mechanisms as primary drivers of sustainable behavior [70]. However, limited research has empirically examined how influencer content activates customer engagement mechanisms—particularly cognitive, emotional, and behavioral engagement—that mediate or moderate the formation of brand loyalty in the sustainable fashion context. This study seeks to address this gap by investigating how Instagram fashion influencers foster sustainable consumption through follower engagement. By synthesizing insights from social influence theory, brand authenticity, and sustainable marketing, this research positions SMIM not only as a marketing strategy but also as a vehicle for cultivating environmentally responsible consumption behaviors.

2.3. The Theory of Stimulus-Organization-Response

The stimulus–organism–response (SOR) theory, initially proposed by Mehrabian and Russell [33] and later extended by Jacoby [32], provides a foundational psychological framework for understanding how external environmental cues influence internal states, which subsequently guide behavioral outcomes. In its basic formulation, the model posits that a stimulus (S)—external environmental input—elicits internal organism (O) reactions involving emotional and cognitive processing, which in turn lead to a response (R)—an observable behavioral outcome [28]. This tripartite structure has proven particularly relevant in consumer behavior studies, where various marketing stimuli evoke affective and cognitive reactions that shape consumption decisions [79].

In the context of social media environments, and particularly within the realm of Instagram fashion influencers, the SOR model serves as a valuable lens to understand how users interpret and act upon influencer-generated content [80]. Influencer content typically consists of curated posts that incorporate visual esthetics, narratives, and brand associations [81]. These stimuli are rich in symbolic meaning and often strategically constructed to evoke specific consumer reactions. When such content promotes sustainable fashion—highlighting elements like ethical sourcing, environmental responsibility, and circular consumption—it serves as a unique class of stimuli that carry both informational and normative weight [82].

Unlike traditional fashion marketing that emphasizes materialism, novelty, or hedonic appeal, sustainable influencer messaging emphasizes values-based cues such as ecological consciousness, authenticity, and ethical responsibility [83,84]. These symbolic stimuli do more than capture attention; they also activate internal evaluative processes related to moral reasoning, self-identity, and value congruence [85]. For instance, a post about upcycled clothing may evoke admiration or guilt-avoidance while simultaneously prompting reflection on personal consumption practices. Such stimuli thus operate on both affective and cognitive levels, shaping the organismic experience in a more multidimensional way than conventional fashion stimuli [86,87].

The “organism” stage is conceptualized in this study as encompassing the multifaceted dimensions of customer engagement—specifically, affective, cognitive, and behavioral engagement—as internal psychological states [28]. Affective engagement involves emotional attachment to the influencer and positive affective responses to the sustainability values promoted. Cognitive engagement reflects mental involvement, such as actively thinking about the brand’s sustainability claims or comparing its practices to one’s own ethical standards [42]. Behavioral engagement, while often regarded as a visible outcome, may also occur internally in the form of intentions to interact, share, or endorse—processes that precede overt loyalty behaviors [28,88]. By positioning engagement within the organismic phase, the model acknowledges that sustainable consumption decisions are not merely reactive but involve deep-seated psychological engagement influenced by the credibility and message framing of the influencer.

The “response” phase in the SOR model represents the behavioral outcomes that emerge from these internal states. In this study, it is operationalized as brand loyalty—specifically, sustained commitment, repurchase intention, and advocacy for sustainable fashion brands [89]. Importantly, green brand loyalty is qualitatively different from conventional loyalty, as it is rooted in shared ethical values, long-term identity alignment, and normative commitment rather than mere satisfaction or habit [90,91,92]. This distinction is critical in the sustainability context, where consumers often act in accordance with personally held environmental beliefs rather than solely hedonic or utilitarian motivations.

By integrating the SOR model into the realm of sustainable digital marketing, this study contributes a nuanced theoretical perspective that links influencer-generated symbolic stimuli to value-driven engagement and loyalty outcomes [93,94,95]. This contextualized application of the SOR framework sheds light on how sustainability narratives communicated through influencers stimulate not only affective resonance but also ethical introspection, ultimately guiding consumers toward responsible consumption behavior. It positions digital influencers as more than marketing agents—they become cultural intermediaries and value transmitters who shape how consumers construct meanings around sustainability and consumption.

2.4. Customer Engagement

Customer engagement (CE) has become a cornerstone of digital marketing theory, particularly in the realm of social media and influencer-based branding, where consumer–brand relationships are increasingly co-created rather than passively received [28]. Defined as a consumer’s behavioral manifestation toward a brand or organization based on motivational drivers, CE reflects the depth of psychological involvement that fosters brand loyalty [96,97]. As consumers become more discerning in their values and media consumption, CE is seen as not only a commercial metric but also a pathway to promoting ethical and sustainable brand choices [98,99]. In digital spaces like Instagram, CE plays a transformative role, enabling consumers to interact with influencer content in ways that extend beyond passive observation to active brand participation. For instance, engaged users share experiences, comment on content, and co-create brand narratives, thereby shaping both consumer perceptions and community influence [100,101]. These forms of engagement are particularly valuable in sustainability-focused branding, where trust, emotional connection, and transparency are critical to building loyalty.

To operationalize CE in the social media context, this study adopts the creation–consumption–contribution (C–C–C) framework developed by Muntinga et al. [102]. This framework captures CE as a dynamic, multidimensional process: creation refers to consumers generating brand-related content; consumption involves interacting with influencer or brand content; and contribution encompasses advocacy or participation in co-creative activities [103,104,105]. These three engagement types offer distinct pathways to building brand loyalty in sustainability-driven influencer contexts. For example, content creation—such as posting original fashion content that supports eco-friendly brands—demonstrates personal identification with sustainability values and strengthens affective commitment [106,107,108]. Consumption, though more passive, involves liking, viewing, or saving posts, which contributes to knowledge acquisition and the internalization of sustainable values [109,110,111]. Meanwhile, contribution, including reposting content or participating in sustainability campaigns, fosters social signaling and reinforces the consumer’s identity as a responsible community member [112,113]. Such distinctions are essential for understanding how each form of engagement contributes uniquely to brand loyalty.

These engagement behaviors are not only expressions of digital participation but also serve as organismic responses within the SOR model, reflecting the cognitive, emotional, and behavioral processes elicited by exposure to sustainability-themed influencer content [114,115]. This study conceptualizes CE as both a mediating mechanism—translating SMIM exposure into internal involvement—and a moderating factor—amplifying or attenuating the influence of sustainable messaging on brand loyalty based on the intensity and type of engagement. The dual role of CE helps illuminate the psychological mechanisms by which digital sustainability narratives influence consumer behavior.

Furthermore, this study embeds CE within the broader concept of sustainable consumption, defined as the use of goods and services that respond to basic needs while minimizing negative environmental impacts [36,42,116]. By mapping CE onto this definition, the study highlights how consumer–brand interactions facilitated by influencers can act as catalysts for value-based consumption. The C–C–C framework thus serves not only as a typology of digital engagement but also as a model for understanding how social media behavior can drive more meaningful and enduring brand loyalty rooted in sustainability values.

2.5. Brand Loyalty

Brand loyalty is a central outcome in digital marketing and sustainable branding, referring to consumers’ continued commitment to a brand through repeat purchasing and advocacy behavior [117]. It is commonly conceptualized as having two dimensions: behavioral loyalty, which involves repeated purchase actions, and attitudinal loyalty, reflecting psychological commitment and emotional attachment [118]. This study emphasizes behavioral loyalty—observable expressions such as repurchase intentions and sustained brand support—which aligns with the outcomes of consumer engagement in social media environments [119].

In influencer-driven ecosystems like Instagram, loyalty is no longer built solely through functional brand attributes but through relational cues and value alignment. SMIM facilitates this by enhancing brand trust, authenticity, and visibility, especially when influencer content reflects followers’ identities and ethical concerns [120,121]. In sustainable consumption contexts, loyalty extends beyond repeat purchases to encompass values-based alignment, where consumers remain loyal because the brand resonates with their beliefs about environmental responsibility and ethical production. For instance, influencers promoting eco-conscious narratives strengthen both brand memory and affective ties among their followers [122], reinforcing brand loyalty as both a consumption behavior and a sustainability commitment.

Thus, brand loyalty in this study is not viewed as a transactional outcome but as a manifestation of sustained engagement and shared ethical values, completing the theoretical chain from stimulus (SMIM) to organism (engagement) to response (loyalty). This conceptualization underscores the strategic role of influencer-driven sustainability messaging in cultivating long-term consumer–brand relationships.

3. Research Model and Hypotheses Development

3.1. Customer Engagement and Brand Loyalty

Customer engagement has been widely recognized as a central driver of brand loyalty, particularly in social media environments where consumers actively interact with content and co-create brand meaning [6,28,121,123]. As digital platforms empower consumers to participate in brand conversations and storytelling, the emotional, cognitive, and behavioral aspects of engagement contribute to deeper and more durable brand relationships [124]. Kamboj et al. [125] emphasized that engaged customers are essential to brand co-creation as they contribute valuable insights and stimulate peer interaction. Influencing factors such as social ties, digital advertisements, and family networks help shape engagement behavior, which in turn enhances brand awareness, strengthens emotional connections, and promotes loyalty [3].

In sustainable consumption contexts, these mechanisms take on added significance. Engagement is not only about transactional value but also about alignment with ethical identity and shared environmental values [126]. Consumers who interact with sustainability-themed content—such as second hand fashion or eco-friendly product endorsements—often experience emotional responses like admiration, pride, or responsibility, which deepen loyalty intentions [7,26]. Such affective and cognitive mechanisms act as internal drivers that convert engagement into loyalty by reinforcing personal values through brand association.

Recent empirical studies continue to affirm this connection across various sectors. Cheng et al. [127] found that customer engagement positively influences brand loyalty, even in the presence of competing brands with strong moral appeal. Similarly, Kini et al. [128] showed that in the FinTech industry, consumer engagement and interaction enhance emotional attachment and strengthen loyalty outcomes. These patterns suggest that the intensity and quality of engagement—not just its frequency—matter significantly in value-driven contexts. Within the fashion industry, where esthetic appeal intersects with ethical consciousness, influencers play a unique role in reinforcing these bonds.

This study builds on these findings by proposing that customer engagement—when activated by sustainability cues from influencers—serves as a central mechanism driving brand loyalty in the digital fashion ecosystem. Engaged consumers who feel a sense of belonging, purpose, or shared values with a brand are more likely to become repeat buyers and advocates [30,129]. Therefore, this study posits the following hypothesis:

Hypothesis 1.

Customer engagement relates positively to brand loyalty.

3.2. Social Media Influencer Marketing, Customer Engagement, and Brand Loyalty

SMIM has become a dominant strategic tool for brands aiming to foster emotional connections and promote loyalty among consumers in digitally mediated environments [130,131]. Defined by key characteristics such as expertise, trustworthiness, attractiveness, and similarity, influencers are increasingly seen as credible sources capable of shaping consumer perceptions and purchase decisions [18,63,64]. These personal attributes enhance the persuasive power of influencer content, making it more relatable and impactful. Empirical studies show that social media activities—including influencer marketing—positively influence brand loyalty and satisfaction, often mediated by constructs such as relationship quality, brand consciousness, and value perception [132,133]. In the context of sustainable consumption, these characteristics help influencers convey ethical and environmental brand values in ways that resonate with eco-conscious consumers, thereby reinforcing value alignment.

Furthermore, the relationship between SMIM and brand loyalty is significantly shaped by the degree of customer engagement it generates. When consumers are emotionally and cognitively engaged with influencer content, they are more likely to develop favorable attitudes toward the associated brand, leading to stronger loyalty [134]. Vacas De Carvalho et al. [135] found that engaged customer involvement—combined with perceived value and brand love—enhances brand loyalty across various contexts, while Prentice et al. [136] highlighted that even without direct brand participation, customer-driven engagement in social media spaces can result in meaningful brand outcomes. These patterns suggest that SMIM operates not only through product visibility but also by stimulating personal identification with sustainability narratives and ethical lifestyles.

In influencer-driven sustainable fashion marketing, the loyalty response is amplified when engagement reflects more than just interest in trends—it signals a psychological bond with the influencer’s ethical message. When influencers promote slow fashion, secondhand consumption, or eco-conscious practices, they serve as both commercial agents and cultural intermediaries who facilitate consumer engagement through value congruence [10,27]. Thus, customer engagement becomes a central organismic mechanism in the SOR framework, mediating how SMIM as a stimulus leads to attitudinal and behavioral loyalty in sustainability contexts. In line with this conceptualization, the following hypotheses are proposed:

Hypothesis 2.

Social media influencer marketing relates positively to customer engagement.

Hypothesis 3.

Social media influencer marketing relates positively to brand loyalty.

Hypothesis 4.

Customer engagement mediates the effects of SMIM on brand loyalty.

3.3. Customer Engagement as a Moderator

Customer engagement has increasingly been recognized not only as a driver of brand loyalty but also as a moderating factor that shapes the strength of the relationship between marketing efforts and brand outcomes. Research has shown that variables such as age [137], blogging behavior [138], and brand-led interaction strategies [139] can moderate the effectiveness of SMIM in driving loyalty. Within the framework of the SOR theory, customer engagement can be positioned as the organismic factor that filters and amplifies consumers’ internal responses to influencer content, ultimately influencing the degree of loyalty formed toward a brand [28]. Engaged customers are more likely to process influencer messages deeply, relate emotionally to brand values, and internalize these communications in a way that leads to sustained brand commitment [140,141].

Moreover, engagement enhances the interactive and participatory dynamics of social media environments, where consumers serve not only as passive recipients but also as active co-creators and advocates of brand meaning [142]. This bidirectional interaction contributes to the formation of strong emotional and behavioral ties, facilitating more meaningful brand relationships [143,144]. When engagement is high, consumers are more inclined to talk about brands, share positive experiences, and reinforce the brand narrative within their communities [145,146]. Conversely, low engagement can weaken the perceived relevance and authenticity of influencer content, reducing its effectiveness [147].

In sustainability-driven fashion consumption, this moderating role becomes particularly salient. Engagement reflects not only interaction frequency but also the consumer’s ethical alignment and emotional investment in eco-conscious narratives. Highly engaged consumers are more likely to internalize sustainability messages conveyed by influencers, enhancing the credibility and persuasive power of SMIM in forming loyalty. This suggests that engagement magnifies the moral and emotional resonance of sustainable brand communication, reinforcing loyalty through shared values and lifestyle alignment. Thus, this study proposes the following hypothesis:

Hypothesis 5.

Customer engagement moderates the effect of social media influencer marketing on brand loyalty.

3.4. Conceptual Model

Grounded in the SOR theory, the conceptual model of this study integrates SMIM as the stimulus, customer engagement as the organism, and brand loyalty as the response. The model is developed to examine both the direct and indirect effects of SMIM on brand loyalty, highlighting customer engagement as a dual-function variable—operating both as a mediator and a moderator. Prior research has emphasized the importance of customer engagement in shaping consumer behavior, emotional investment, and brand advocacy [140,142,144]. By incorporating dimensions such as creation, consumption, and contribution [103,104,105], this model reflects the dynamic and participatory nature of consumer–brand relationships in social media environments. Moreover, the conceptualization recognizes that in sustainable consumption contexts, engagement entails not only interactivity but also ethical alignment, whereby consumers evaluate brands based on environmental and social values conveyed through influencer narratives [36,42,116]. The inclusion of customer engagement in both mediating and moderating roles reflects its centrality in driving loyalty, particularly in sustainability-focused markets where consumers increasingly align their behaviors with influencers and brands that reflect their values [145,147]. The proposed relationships among the variables are illustrated in Figure 1.

4. Methods

4.1. Study Design and Sample

This study employed a quantitative, cross-sectional survey design to test the hypothesized relationships within the proposed SOR framework. The primary focus was on Instagram users who follow fashion influencers engaged in sustainable fashion content. Given the exploratory nature of the study in the domain of sustainable consumption, this design is consistent with previous research in influencer marketing and consumer behavior [4,5,18,148].

To enhance the study’s contextual relevance and ecological validity, we specifically targeted followers of mid-tier fashion influencers—those with 10,000 to 100,000 followers [149,150]. Mid-tier influencers are increasingly recognized in the SMIM literature for achieving a balance between authenticity and reach, as they tend to develop closer relationships with their audiences compared to macro or celebrity influencers [12,71,151]. Their influence is particularly pronounced in areas such as sustainable fashion, where perceived credibility and engagement are essential to shaping consumer loyalty and value alignment [152,153,154].

A purposive sampling approach was adopted to ensure relevance and alignment with the study objectives. Participants were eligible if they (1) were at least 18 years old, (2) used Instagram regularly, and (3) followed at least one fashion influencer based in Palestine. The focus on Palestine reflects a culturally specific context where sustainable consumption is emerging within digital consumer culture, especially among younger audiences [155,156]. To reduce ambiguity, participants were presented with a working definition of social media fashion influencers as individuals who consistently post about fashion or lifestyle topics and maintain a considerable and engaged online following [157]. Respondents were instructed to answer survey items in reference to a specific fashion influencer whom they follow and feel most connected to.

The survey was distributed via online channels, including Instagram story links, direct messages, and influencer collaborations. Out of 650 distributed invitations, 310 users initiated the survey. After excluding incomplete or inconsistent responses, a final sample of 279 valid cases was retained, resulting in a usable response rate of approximately 43%, which is acceptable for social media-based consumer research [158,159,160].

Descriptive statistics revealed that 65% of respondents identified as female, and 63.7% were aged between 18 and 34 years. This demographic profile is consistent with earlier research identifying young, female users as the primary audience for fashion influencer content on Instagram [58,148,161,162,163]. This alignment with the dominant user demographic of Instagram-based sustainable fashion communities strengthens the representativeness and generalizability of the study findings.

4.2. Measurement

All constructs in this study were measured using established multi-item scales adapted to fit the context of Instagram-based fashion influencer marketing. The questionnaire was originally developed in English, translated into Arabic, and then back-translated into English using Brislin’s [164] translation and reverse translation method to ensure semantic equivalence. A pilot test with 30 active Instagram users confirmed the clarity of the items and the reliability of the scales, with Cronbach’s alpha values exceeding 0.70. Responses were recorded on a seven-point Likert scale ranging from 1 = “strongly disagree” to 7 = “strongly agree”. SMIM was assessed using 18 items capturing four key attributes: expertise, trustworthiness, and attractiveness, and similarity [165,166,167]. Customer engagement was operationalized as a multidimensional construct including consumption, contribution, and creation behaviors, each measured using four items based on Cao et al. [103] and Schivinski et al. [104]. Lastly, behavioral brand loyalty was measured using four items adapted from Aljuhmani et al. [28] and Samarah et al. [121], reflecting consumer attachment and repeat engagement within the digital fashion context. These measures collectively ensured the validity and robustness of the model in capturing consumer behavior in influencer-driven, sustainability-oriented marketing environments.

4.3. Common Method Bias

Given the cross-sectional nature of this study, common method bias (CMB) was assessed to ensure the validity of the results, as it is a common concern in survey-based research where data are collected from a single source [168]. Harman’s single-factor test was conducted to examine whether a single factor accounted for most of the variance. The results revealed that the first factor explained only 39.7% of the total variance—well below the recommended threshold of 50%—indicating that CMB is not a major issue in this study [169]. In addition, variance inflation factors (VIFs) were calculated for all latent constructs, and all values were found to be below 3.3, suggesting that multicollinearity is not a concern and further confirming the absence of significant CMB [170,171]. These diagnostic checks provide assurance that the findings of this study are not unduly influenced by measurement bias.

5. Data Analysis and Results

To test the proposed conceptual model and hypotheses, this study employed Partial Least Squares Structural Equation Modeling (PLS-SEM) using SmartPLS 4.0 [172]. PLS-SEM is particularly suitable for prediction-oriented research and complex models, as it does not assume multivariate normality and allows for simultaneous assessment of measurement and structural models [173,174]. This analytical approach aligns with the study’s objective to predict how SMIM shapes brand loyalty through customer engagement within the sustainable consumption context [175]. Following best practices in the PLS-SEM literature, we implemented a two-stage analytical procedure [176,177]. The first step involved validating the measurement model to assess reliability and validity, while the second step evaluated the structural model to examine hypothesized relationships and predictive accuracy [170]. This method ensures the robustness and empirical rigor required for theory-driven yet prediction-focused research in social media marketing and sustainable consumer behavior.

5.1. Measurement Model Assessment

The reliability and validity of the measurement model were assessed using PLS-SEM. Internal consistency reliability was first evaluated through Cronbach’s alpha and composite reliability (CR), both of which exceeded the commonly accepted threshold of 0.70 for all constructs, indicating strong consistency among the indicators [170]. Inter-item reliability was then confirmed by analyzing standardized factor loadings, where all items loaded above 0.70, signifying adequate indicator relevance [178], except BL2, which was removed due to low factor loading. Convergent validity was assessed via average variance extracted (AVE), with all constructs demonstrating AVE values greater than the recommended minimum of 0.50, confirming that each construct explained a sufficient portion of variance in its indicators [179]. The results for factor loadings, AVE, Cronbach’s alpha, and CR are presented in

Table 1. Reliability and convergent validity assessment.

Constructs/Items	Outer Loadings	VIF	Cronbach’s Alpha	CR	AVE
Social Media Influencer Marketing (SMIM)			0.940	0.946	0.697
Expertise (EXPR)			0.896	0.923	0.707
EXPR1	0.823	1.630
EXPR2	0.865	1.529
EXPR3	0.851	2.290
EXPR4	0.857	2.147
EXPR5	0.807	1.840
Trustworthiness (TRST)			0.919	0.940	0.757
TRST1	0.757	1.591
TRST2	0.883	1.943
TRST3	0.905	2.294
TRST4	0.899	2.639
TRST5	0.898	2.436
Attractiveness (ATRC)			0.939	0.954	0.806
ATRC1	0.870	2.451
ATRC2	0.928	2.663
ATRC3	0.939	2.491
ATRC4	0.922	2.220
ATRC5	0.825	2.571
Similarity (SMLR)			0.874	0.922	0.798
SMLR1	0.892	2.505
SMLR2	0.909	2.099
SMLR3	0.879	2.456
Customer Engagement (CE)			0.898	0.915	0.676
Consumption behavior (CECSB)			0.872	0.913	0.726
CECSB1	0.737	1.688
CESCB2	0.920	1.889
CESCB3	0.900	2.081
CESCB4	0.839	1.969
Contribution behavior (CECTB)			0.855	0.902	0.698
CECTB1	0.771	2.297
CECTB2	0.829	1.765
CECTB3	0.869	1.904
CECTB4	0.896	2.155
Creation behavior (CECAB)			0.837	0.891	0.672
CECAB1	0.795	1.630
CECAB2	0.838	1.529
CECAB3	0.880	2.290
CECAB4	0.833	2.147
Brand Loyalty (BL)			0.850	0.909	0.769
BL1	0.877	2.028
BL2 *	-	-
BL3	0.891	2.282
BL4	0.863	1.983

Note: VIF = variance inflation factor; AVE = average variance extracted; CR = composite reliability. * = item was removed due to low factor loading.

.

To examine discriminant validity, the Heterotrait–Monotrait ratio (HTMT) was employed, as it offers a more robust assessment than the traditional Fornell-Larcker criterion [180]. All HTMT values were below the conservative cut-off of 0.90, indicating that each construct was empirically distinct from the others [170]. These HTMT results are summarized in

Table 2. Discriminant validity assessment.

Constructs	1	2	3
1. Brand loyalty	0
2. Customer engagement	0.603	0
3. Social media influencer marketing	0.585	0.487	0

. These results collectively confirm that the measurement model satisfies all essential psychometric criteria, providing a reliable and valid foundation for the subsequent structural model analysis focused on how fashion influencers impact brand loyalty through customer engagement in sustainable digital environments.

5.2. Structural Model Assessment

The structural model was assessed following established procedures in the PLS-SEM literature to examine the predictive relationships among the study variables and validate the proposed hypotheses [170]. Using SmartPLS 4.0 and a bootstrapping procedure with 5000 resamples [175], the path coefficients and their significance levels were estimated. Figure 2 presents the structural model, illustrating the hypothesized relationships among SMIM, customer engagement, and brand loyalty. The results supported all three direct hypotheses. Specifically, customer engagement was found to have a significant positive impact on brand loyalty (β = 0.300, p < 0.001), supporting H1. Similarly, SMIM significantly predicted both customer engagement (β = 0.717, p < 0.001) and brand loyalty (β = 0.351, p < 0.001), confirming H2 and H3, respectively. These results underscore the importance of influencer-driven engagement in fostering sustainable brand relationships.

To test the mediating role of customer engagement between SMIM and brand loyalty, this study followed the bootstrapping approach for indirect effect testing recommended by Preacher and Hayes [181]. The analysis revealed that customer engagement significantly mediates the relationship between SMIM and brand loyalty (β = 0.215, p < 0.010), providing full support for H4. This finding implies that while SMIM directly enhances brand loyalty, a considerable portion of its influence operates through the behavioral engagement of consumers. Thus, customer engagement functions as an essential conduit through which influencer marketing impacts brand commitment within the sustainable consumption context. As reflected in

Table 3. Summary of hypotheses testing results.

Relationships	β	SE	t-Values	p-Values	CIs		Results
					2.5%	97.5%
H1: CE → BL	0.300 ***	0.085	3.532	0.000	0.131	0.467	Accepted
H2: SMIM → CE	0.717 ***	0.038	18.431	0.000	0.663	0.773	Accepted
H3: SMIM → BL	0.351 ***	0.076	4.621	0.000	0.190	0.489	Accepted
H4: SMIM → CE → BL	0.215 **	0.063	3.429	0.001	0.094	0.343	Accepted
H5: SMIM × CE → BL	0.097 *	0.039	2.489	0.013	0.023	0.173	Accepted

Note: CE = customer engagement; BL = brand loyalty; SMIM = social media influencer marketing; CIs = confidence intervals; SE = standard error. * p < 0.05; ** p < 0.01; *** p < 0.001.

, the mediation was partial, confirming that both direct and indirect pathways play a role in influencing brand loyalty.

The moderating effect of customer engagement on the SMIM–brand loyalty relationship was assessed using the product indicator approach in PLS-SEM [182,183]. The interaction term (SMIM × CE) was found to be statistically significant (β = 0.097, p < 0.050), thus supporting H5. This suggests that higher levels of customer engagement amplify the positive effect of SMIM on brand loyalty. In other words, when followers are more actively engaged with influencer content—through consumption, creation, or contribution behaviors—their loyalty to the endorsed brand strengthens considerably. The moderating effect is illustrated in Figure 3, which shows a steeper slope in the SMIM–brand loyalty relationship under high engagement conditions, visually confirming that customer engagement enhances the strength of this connection.

5.3. Predictive Power of the Structural Model

The predictive capability of the structural model was evaluated using the coefficient of determination (R²), which indicates the amount of variance explained by the model’s endogenous constructs. As recommended by Falk and Miller [184], R² values exceeding 0.10 suggest acceptable explanatory power. The model explained 40.7% of the variance in brand loyalty and 51.5% in customer engagement, indicating moderate to substantial predictive strength. Additionally, the moderating effect of customer engagement was assessed by comparing the R² values of the main and full models following Henseler and Fassott [185]. The resulting effect size (f²) was calculated using Cohen’s [186] formula and yielded a value of 0.182, reflecting a moderate contribution of the moderating variable. These results underscore the robustness of the model in explaining the dynamics of influencer marketing, customer engagement, and brand loyalty within sustainable consumption contexts.

6. Discussion and Implications

6.1. Discussion of Key Findings

This study investigated how Instagram fashion influencers cultivate brand loyalty through customer engagement within the context of sustainable consumption. The findings reaffirm that customer engagement serves as both a critical predictor and mechanism for enhancing brand loyalty, aligning with research that positions engagement as central to fostering meaningful consumer–brand relationships in digital spaces [28,30,100,101,128]. Consumers who actively consume, contribute to, and create content around fashion influencers demonstrate stronger emotional bonds and behavioral loyalty, particularly when sustainability narratives are embedded in the brand’s positioning [103,136]. This multidimensional engagement is not merely transactional—it reflects a co-creative, participatory process through which ethical consumers find alignment with a brand’s values, contributing to a deeper and longer-lasting form of loyalty.

The results also underscore the importance of SMIM in shaping both engagement and loyalty outcomes. Influencer attributes—such as trustworthiness, similarity, expertise, and attractiveness—remain foundational to follower trust and interaction [114,130]. However, this study expands on previous research by contextualizing these effects within sustainability-driven consumption, showing that the persuasive strength of influencers intensifies when their values align with those of environmentally conscious consumers [161,187]. These findings emphasize the dual nature of influencers as both brand ambassadors and ethical communicators, where authenticity and congruence significantly influence how followers engage with and remain loyal to sustainable fashion brands.

Critically, the study provides novel insights into the moderating role of customer engagement in the relationship between SMIM and brand loyalty. While prior research has largely focused on engagement as a mediator, this study shows that highly engaged consumers amplify the effectiveness of influencer marketing, particularly in sustainability contexts. This amplification may stem from stronger emotional attachment, shared identity, and value congruence, where followers perceive the brand’s sustainable messaging as personally meaningful. Drawing on theories of participatory marketing and the C–C–C engagement model, such consumers do not passively absorb influencer content—they actively reshape and circulate brand narratives through interactive behaviors [36,42,116]. These findings also strengthen the application of the SOR framework [28,33], demonstrating how consumer engagement (organism) not only processes but also intensifies the effect of SMIM (stimulus) on brand loyalty (response).

Moreover, this study addresses a noted gap in the sustainability marketing literature by integrating the SOR theory with the C–C–C model within a sustainable influencer marketing framework. While past studies have examined influencer effects in generic or transactional contexts, few have simultaneously assessed the dual mediating and moderating influence of customer engagement in sustainability-focused scenarios. This integration underscores that brand loyalty in sustainable fashion markets is co-constructed through ethical alignment, emotional resonance, and active audience participation.

In conclusion, the findings position customer engagement as a strategic lever in sustainable fashion branding on Instagram. Brands aiming to foster loyalty should not only select influencers based on credibility and relevance but also design content strategies that stimulate multidimensional engagement, particularly among ethically aware audiences. By doing so, they tap into a participatory ecosystem where consumers become co-authors of the brand’s sustainability story, strengthening not just brand loyalty but also the legitimacy of the brand’s ethical positioning.

6.2. Theoretical Implications

This study offers several important contributions to the theoretical understanding of sustainable consumption, digital marketing, and consumer engagement. First, by applying the SOR framework [33], the study enriches theory by demonstrating how SMIM acts as a digital stimulus that activates consumer engagement as an internal processing mechanism (organism), which subsequently influences behavioral outcomes such as brand loyalty (response). This finding aligns with prior research that emphasizes psychological pathways linking digital marketing stimuli with consumer behavior in ethical consumption settings [25,28]. By positioning customer engagement as both a mediating and moderating construct, the study extends the SOR model, illustrating that engagement does not merely transmit effects but also conditions the strength of the SMIM–loyalty pathway, especially in contexts where values and ethics are salient.

Second, the application of the creation–consumption–contribution (C–C–C) engagement model [102,103,104] provides a more nuanced understanding of consumer participation in digital environments. Unlike traditional cognitive–affective–behavioral models [114,121], which often depict engagement as linear or unidimensional, the C–C–C framework recognizes the layered and participatory nature of consumer behavior. This study deepens the theoretical value of this model by showing how sustainability-oriented consumers engage at different levels—not just by passively consuming content but also by co-creating brand meaning and reinforcing brand values through interaction, advocacy, and creative output. This multidimensionality enhances theoretical conceptualizations of engagement in sustainability marketing.

Third, this study advances influencer marketing theory by reaffirming the importance of perceived influencer attributes—trustworthiness, attractiveness, expertise, and similarity—in fostering digital engagement and loyalty [165,166,167]. However, the present findings move beyond existing transactional perspectives by contextualizing these influencer traits within sustainability-oriented communication. Specifically, the credibility and perceived ethical alignment of influencers play a critical role in shaping emotional attachment and long-term brand commitment among sustainability-conscious consumers [36,42,116]. This contributes to the broader literature on value congruence, emphasizing how shared ethical beliefs and identity alignment between consumers and influencers can act as strong psychological drivers of loyalty.

Fourth, the study addresses a notable theoretical gap by integrating the SOR framework with the C–C–C engagement model in the context of sustainable consumption. This dual-framework integration is rare in the existing literature, and it allows for a more holistic conceptualization of how digital stimuli, participatory engagement, and ethical considerations interact to shape brand loyalty outcomes. By doing so, the study offers a theoretical bridge between stimulus-driven and co-creation-driven models of consumer behavior—two strands of research that are often treated separately.

Finally, this study contributes to the theoretical development of sustainable consumption by conceptualizing it as an interactive and identity-driven behavior, rather than a passive preference. The findings suggest that in the context of Instagram fashion influencers, sustainable consumption is expressed through social interaction, creative participation, and ethical signaling. This insight adds depth to sustainability marketing theory by reframing sustainable behavior as a co-constructed outcome of social influence, emotional alignment, and participatory action within digital ecosystems.

6.3. Practical Implications

This study provides actionable guidance for brands operating in the sustainable fashion space by highlighting how strategic use of SMIM can foster customer engagement and long-term brand loyalty. The findings reveal that customer engagement not only mediates but also moderates the relationship between SMIM and brand loyalty, underscoring its critical role in enhancing digital brand outcomes. To capitalize on this dynamic, fashion brands should partner with influencers whose personal values visibly align with sustainable consumption principles. Such influencers—who communicate authenticity, credibility, and ethical responsibility—are more likely to resonate with environmentally conscious audiences and reinforce brand trust [2,165].

In selecting influencers, brands must go beyond esthetics and promotional reach, prioritizing alignment with eco-conscious practices such as promoting slow fashion, fair trade, or climate-positive initiatives [10,27,188]. When followers perceive congruence between the influencer’s lifestyle and the brand’s sustainability mission, they are more likely to engage meaningfully and remain loyal over time. This authenticity is essential in avoiding consumer skepticism, particularly in sustainability-driven markets where greenwashing is a growing concern [4,35,187].

Moreover, the study supports designing engagement strategies that stimulate participation across all three dimensions of the C–C–C model: consumption, contribution, and creation [102,103,104]. Brands can use Instagram features like Reels to spotlight sustainable production processes, Stories to launch eco-awareness polls, and “Swipe Up” links to guide followers toward environmentally responsible product collections [189]. These interactive elements encourage deeper engagement and foster emotional attachment by inviting consumers into the brand’s ethical narrative.

To further leverage participatory engagement, brands should encourage user-generated content (UGC) through eco-challenges (e.g., #GreenClosetChallenge), behind-the-scenes content co-creation, and digital storytelling campaigns that invite followers to share their own sustainability journeys [190,191]. This fosters community belonging and strengthens co-creation between brands and consumers. For example, inviting followers to showcase their thrifted outfits or DIY fashion hacks enhances both visibility and ethical resonance.

Importantly, these strategies should be anchored in a clear and multidimensional understanding of sustainable consumption, which includes environmental stewardship, ethical labor practices, and long-term well-being. Brands must ensure that their influencer collaborations reflect these principles in both message and action. Promoting certifications (e.g., B Corp, Fair Wear Foundation), transparent supply chains, or product life-cycle disclosures can build credibility and strengthen loyalty among ethically attuned consumers [192,193].

In summary, this study reinforces the idea that building loyalty in sustainable fashion is not merely a function of marketing tactics but of value-based alignment and consumer participation. By embedding sustainability into both content and collaboration strategies, brands can transform followers from passive consumers into co-authors of an eco-conscious brand narrative—driving both market differentiation and long-term loyalty in an increasingly values-driven digital economy.

6.4. Limitations and Future Research Directions

While this study provides important insights into how Instagram fashion influencers shape sustainable consumption through customer engagement, it is not without limitations. First, the use of a cross-sectional design limits our ability to infer causality among the study variables. Although relationships between stimulus (influencer credibility and sustainability content), organism (engagement dimensions), and response (brand loyalty) were theorized and supported, causality cannot be firmly established. Future research should employ longitudinal or experimental designs to better understand the temporal sequencing and cumulative effects of influencer strategies on consumer attitudes and behaviors [168,194].

Second, the generalizability of the findings is constrained by the sample’s geographic and demographic focus—Instagram users in Palestine, a context shaped by unique socio-political, cultural, and economic realities [155,156]. While this offers valuable contributions to underrepresented regions in influencer marketing research, the findings may not fully translate to other cultural or economic environments. In particular, Palestinian consumers may face limitations in accessing sustainable fashion options due to lower purchasing power and restricted product availability, which could attenuate the influence of pro-sustainability messages on actual behavior. Future studies should conduct cross-cultural comparisons or replicate the study in both developing and developed markets to better capture contextual differences in how sustainability messages are received and acted upon [195].

Third, while the focus on micro-influencers provided a relevant lens into trust-based digital engagement, future research could compare different tiers of influencers (nano, micro, macro, celebrity) to assess variations in credibility, content impact, and sustainability messaging efficacy [12,150]. Additionally, although the study applied the C–C–C framework to capture behavioral engagement [102,103], future research could integrate emotional or cognitive aspects of engagement—such as environmental concern, identification, or value congruence—to develop a more holistic model of sustainable influence [8,42]. Further extensions might also explore downstream outcomes like green purchase intention, digital activism, or long-term brand commitment to evaluate the broader societal impact of influencer-led sustainable marketing efforts.