Digital Influencers Promoting Healthy Food: The Role of Source Credibility and Consumer Attitudes and Involvement on Purchase Intention

Abstract

This article investigates the influence of digital influencers on healthy food purchase intention within the context of Instagram. The research model is guided by the theory of source credibility and the elaboration likelihood model. A quantitative approach was employed, and data were collected through an online survey from Instagram users in Portugal (n = 221). A set of ten hypotheses was tested using structural equation modeling (SPSS-AMOS). The findings corroborated that purchase intention of healthy foods is positively influenced by digital influencer perceived credibility, involvement with healthy foods, and attitude toward advertising on Instagram. The findings also confirmed that involvement with healthy foods and with Instagram affect advertising avoidance behavior, and that these three constructs affect attitude toward advertising on Instagram. However, the expected relationship between attitude toward advertising and digital influencer credibility was not confirmed. The study contributes to the literature on influencer marketing, specifically in the context of healthy food, and it provides valuable insights for social media marketers and brand managers interested in adopting influencer marketing to leverage their communication effectiveness.

1. Introduction

Recently, influencer marketing has received much attention in market research [1,2,3,4]. This marketing strategy is defined by Leung, Gu, and Palmatier [3] as “a strategy in which a firm selects and incentivizes online influencers to engage their followers on social media in an attempt to leverage these influencers’ unique resources to promote the firm’s offerings, with the ultimate goal of enhancing firm performance” (p. 226). Through incorporating digital influencers into their communication strategies, firms gain access to unique resources possessed by these influencers, such as their follower base and the authority they hold among their followers. It also helps overcome the growing skepticism toward more traditional marketing techniques, such as advertising [5]. As a result, the market value of influencer marketing is estimated to have more than doubled globally between 2019 and 2022, and is projected to reach a value of US$21.1 billion in 2023 [6].

Digital influencers are the main actors of influencer marketing, serving as intermediaries between brands and consumers. Ki and Kim [7] define digital influencers as “people who have established credibility with large social media audiences because of their knowledge and expertise on particular topics, and thereby exert a significant influence on their followers’ and peer consumers’ decisions” (p. 905). As noted by Pradhan et al. [1], this concept is often used interchangeably with “opinion leaders, bloggers, YouTube influencers, micro-celebrity, nano-celebrity, and Instagram influencers” (p. 12). Hudders et al. [8] further explain that influencers are social media users who have achieved online fame and amassed a substantial number of followers through their creation and dissemination of online content on various social media platforms. In general, digital influencers distinguish themselves from regular social media users by their extensive reach and influential impact [8]. Consumers perceive them as sharing information based on their personal sensibilities and interests [4]. As content creators and communicators, these individuals establish a prominent online presence and cultivate a dedicated base of followers, allowing them to form partnerships with brands and promote a wide range of products and services to their audience. For managers, it is essential to understand the digital influencer mechanisms in order to make informed decisions on the investments and further understand the efficacy of influencer marketing. Due to their perceived credibility and trustworthiness, digital influencers have a significant impact on their followers’ consumer behavior and preferences.

As demonstrated by Vrontis et al. [2], the literature on influencer marketing primarily focuses on understanding consumer outcomes such as engagement, attitudes, and purchase intention; this is typically achieved by examining source characteristics, followers’ psychological factors, and content attributes. However, further research is urgently required to explore a comprehensive range of factors that can explain the desired outcomes of influencer marketing [1,2], namely to help firms enhance the effectiveness of their marketing strategies [5,8]. In line with this, Vrontis et al. [2] recommend that the scope of research should be expanded to include different product categories, including food, that are endorsed by digital influencers. These authors also recommend using robust theoretical frameworks to produce relevant theoretical and practical contributions, as extant literature on influencer marketing often lacks cohesive theoretical foundation [2]. As a result, there is a growing need for additional studies that offer comprehensive analyses of influencer marketing within specific product categories and employ robust analytical frameworks.

To address these research gaps, assisting practitioners increasingly interested in influencer marketing, this study examines the impact of digital influencers on healthy food purchase intention. Health and wellness represent a prominent domain within influencer marketing [9] that is rapidly expanding the consumer market [10]. Moreover, this sector is important for consumer market growth and the relevance of adopting healthier consumption, as it increases well-being and contributes to overall sustainable development. Influencers play a significant role in inspiring consumers to adopt healthier lifestyles and utilize health products they endorse, particularly in Europe [11]. As explained in detail in the following section, this study is guided by the theory of source credibility [12] and the elaboration likelihood model [13]. These theoretical foundations have facilitated the development of a research framework that combines source credibility, ad avoidance, consumer involvement, and consumer attitudes as factors influencing purchase intention.

Regarding main concepts, this article considers consumer involvement (either with product or social media platforms) as representing the level of relevance of its object considering the values and interests of the consumer [14], and source credibility, in the case of a digital influencer, as the perceived expertise, trustworthiness, and attractiveness [12] that favors the acceptance of the influencers’ messages by her followers. Other concepts important for this study are advertising avoidance, defined as the cognitive and behavioral actions to reduce the exposure to ads [15,16], and attitude toward advertising, particularly the one conveyed by a social media platform, understood as consumers’ cognitive, conative and affective evaluations of its object [13]. Together, these constructs provide relevant effects that shape consumers behaviors, particularly purchase intentions, which is the main dependent variable of this study.

In line with extant literature, this study considers source credibility a key variable in explaining the effectiveness of influencer marketing strategies [1,2,8]. However, it also recognizes that consumers’ involvement with healthy food is a crucial starting point for understanding the purchase process in this product category, in line with recent literature [17]. Hence, by combining two theoretical perspectives, this study aims to provide a greater understanding of the impact of digital influencers on their followers’ purchase intentions. As shown in detail in the next section, this study posits that purchase intention is explained by digital influencer credibility, attitude toward advertising, product involvement and involvement with social media platform, whereas, advertising avoidance can also play a relevant role, namely by its expected effects on attitude.

The remainder of the article is organized as follows. The next section provides the theoretical background that informed the development of ten hypotheses. Subsequently, the method adopted in the empirical study to test these hypotheses is presented. The article then proceeds to present and discuss the obtained results. Finally, the last section is dedicated to the conclusions, emphasizing the theoretical contributions and managerial implications.

2. Background

The guiding research question for this article is: ‘How do digital influencers impact healthy food purchase intention?’. To address it, this study combines contributions from two main theoretical underpinnings: the theory of source credibility (TSC) and elaboration likelihood model (ELM).

In light of TSC, Ohanian [12] defines source credibility as “communicator’s positive characteristics that affect the receiver’s acceptance of a message” (p. 41). In early communication research, the concept of source credibility was primarily associated with expertise and trustworthiness. However, advertising research highlighted the significance of physical attractiveness of the product endorser. This outcome led Ohanian [12] to propose a three-factor construct of source credibility, encompassing expertise, trustworthiness, and attractiveness. In such a context, expertise is the perception of the influencer’s knowledge, skill, and authority. Trustworthiness relates to the influencer’s integrity and honesty. Attractiveness refers to the influencer’s appeal (e.g., physical) and likability. Ohanian’s work sparked a rich body of literature on celebrity endorsement, which has been extended to the realm of digital influencers. In the context of digital influencer studies, perceived source credibility plays a vital role in explaining the effectiveness of this marketing strategy; it has been shown to have significant positive impacts on brand attitude, brand image, and purchase intention, among other outcomes [1,2]. Ooi et al. [18] recommend studying the relationship between influencer credibility and consumer attitudes, as this ultimately influences purchasing behavior. These authors stress that the empirical evidence regarding the impact of source credibility on the effectiveness of influencer marketing is limited and, hence, should be further explored [18].

ELM provides a complementary underpinning to explain the impact of digital influencers on consumers. According to Petty and Cacioppo [13], the ELM is a general theory to explain the effectiveness of persuasive communications, namely through communication-induced attitude change. Persuasion is defined by Masuda et al. [4] as “a process targeted at changing a person’s attitude or behavior” (p. 3). The ELM proposes two routes to persuasion: the central route and the peripheral route [13]. The central route involves thoughtful consideration of arguments central to the issue, while the peripheral route relies on affective associations or simple inferences tied to peripheral cues. The route taken depends on the level of elaboration likelihood in the persuasion situation. Persuasion through the central route leads to more persistent, resistant, and behavior-predictive attitude changes compared to persuasion through the peripheral route. According to the ELM, the extent of elaboration of a message can be seen as a continuum ranging from minimal thought about the relevant information presented to complete elaboration of every argument and integration of these elaborations into the individual’s attitude schema. The likelihood of elaboration is influenced by an individual’s motivation and ability to evaluate the message [13]. Consequently, consumer involvement stands out as an essential motivational determinant of persuasion message processing. Involvement refers to the personal relevance of the message [13].

The combination of these two theories provides a wider understanding of the impact of digital influencers on their followers’ purchase intentions, as it enables to complement the effect of source credibility with other aspects of consumer psychology, namely their attitudes and involvement. In fact, each of these theories explain persuasion from a different perspective: TSC highlights the role of the credibility of the influencer in changing consumer behavior, and the ELM justifies this change in the way the consumer processes the message, in which involvement plays a determinant role. Interestingly, the combination of these two theories is not frequent in digital influencer literature and, as shown in this article, provides a more comprehensive view of the phenomenon.

2.1. Product Involvement

Zaichkowsky [14] defined consumer involvement as “a person’s perceived relevance of the object based on inherent needs, values, and interests” (p. 342). According to the author, this definition is adaptable to several aspects of consumer behavior, such as consumer involvement with products and advertising. Depending on their level of involvement, consumers will exhibit varying degrees of interest in specific products or stimuli. This will influence their attitudes, they search intensity for alternative products, and the complexity of their decision-making process.

One facet of consumer involvement is the involvement with products. Recent literature has emphasized the significance of both low and high product involvement in understanding consumer evaluations within the context of influencer marketing, particularly in relation to healthy food [17]. Involvement with products, such as healthy foods, prompts consumers to study and strengthen their beliefs regarding their consumption. When consumers are involved with a particular product, they naturally become more open to communication related to that product. Moreover, they are willing to invest more time gathering information about such products [14,19,20,21]. Overall, consumers may experience temporary situational product involvement during the purchase decision process, however, there is also enduring involvement with certain types of products, leading to sustained interest and arousal towards the product [14] regardless of the purchase decision stage. As a result, the level of involvement with a product influences consumers’ emotional outcomes [22].

Among the most acknowledged consequences of consumer involvement with a product is increased purchase intention [19,23,24]. In the influencer marketing realm, Cabeza-Ramirez et al. [25] hypothesized that product involvement positively affects consumers’ intentions to purchase the products recommended by digital influencers. Therefore, it is expected that:

Hypothesis 1 (H1).

Involvement with Healthy Food positively influences Purchase Intention.

While facilitating specific communication, involvement with a specific product diminishes consumer interests in advertising for alternative offerings. The literature suggests that consumer involvement enhances the likelihood of resistance and rejection towards advertising messages [13]. This can be explained by the fact that involvement with certain types of products leads to sustained interest and arousal towards the product and reduces their willingness to search for alternatives [14]. Consequently, it makes the consumer less willing to pay attention to alternative offers [14] and consequently, avoid ads. To this end, authors such as Kelly et al. [16] conceptualize advertising avoidance as a relevant behavioral response by consumers that ultimately results in not paying attention and actively ignoring ads (see Section 2.3). Hence, consistent with the assumption that product involvement leads to advertising avoidance, this study hypothesizes that:

Hypothesis 2 (H2).

Involvement with Healthy Food positively influences advertising avoidance.

However, another of the expected outcomes of product involvement is a positive impact on the attitude towards advertising. In general, product involvement makes the consumer more motivated and willing to process information [13]. High involvement is also typically linked to positive emotions [22]. Consumers with higher involvement with a product find information about it more relevant, increasing the likelihood of engaging in cognitive processes such as evaluating the benefits of the product and the featured brand [21,26], positively influencing advertising effectiveness [21], namely in terms of favorable attitudes toward advertising [24]. The relationship between product involvement and consumer attitudes in the context of digital influencers was corroborated by Cabeza-Ramirez et al. [25]. In line with these contributions, product involvement is expected to enhance attitude toward advertising on the social media platforms. Therefore, it is assumed that:

Hypothesis 3 (H3).

Involvement with Healthy Food positively influences Attitude towards Ads on Instagram.

2.2. Consumer Involvement with the Social Media Platform

Another facet of consumer involvement in the context of influencer marketing is the involvement with the social media platform. Indeed, social media users may perceive these platforms as particularly relevant, considering their needs and interests, resulting in high involvement [14]. One way to understand consumer involvement with social media platforms is to consider, as suggested by Voorveld et al. [27], “the emotional, intuitive experiences or perceptions that people undergo when using a particular medium at a particular moment” (p. 40). Consumers highly involved with social media platforms increasingly use them as primary channels of information [28] and dedicate more time and attention to messages conveyed by this type of medium. According to the principles of ELM [13], communication disseminated through these platforms is expected to be more persuasive to highly involved consumers, as they are more likely to consider the arguments and form affective associations with the messages conveyed through these social media platforms.

In line with this, it can be argued that consumers who are highly involved with social media platforms, such as Instagram, are more exposed to digital influencers and perceive their recommendations as more relevant [28]. Highly involved consumers tend to have more positive evaluations of the advertising conveyed by the platform [27], which ultimately includes the content and recommendations shared by digital influencers. Therefore, it can be inferred that high involvement with social platforms is expected to be associated with more favorable evaluations of digital influencers. Digital influencers, such as Instagrammers, are essential channels of marketing communication and gained high perceived credibility by consumers [7]. Moreover, their credibility is generally manifested in terms of expertise, trustworthiness, and attractiveness [12]. Based on these contributions, it is hypothesized that:

Hypothesis 4 (H4).

Involvement with Instagram positively influences Instagrammer Credibility.

Voorveld et al. [27] examined the relationship between user involvement on social media platforms and their engagement and evaluation of featured advertising. The authors argue that users’ experience of advertising on social media is influenced by the interaction between the platform and the advertising content. Therefore, social media platforms play a crucial role in the effectiveness of advertisements. Moreover, user involvement with a social media platform extends to their engagement with the advertising within the platform ultimately impacting their evaluations of the advertisements. Given that attitudes toward advertising are a component of consumer evaluations, it can be inferred that platform involvement also affects attitudes toward the advertisements featured on the platform. Voorveld et al. [27] found evidence of a positive relationship between social media platform involvement and advertising evaluations, namely on Facebook. In the case of Instagram, experiences of innovation and stimulation were found to being associated with more positive Instagram advertising evaluations by users [27] In particular, consumers evaluate advertising in a more positive manner when they experience social media platforms as useful in terms of advice and ideas [27], which is considered an indicator of consumer involvement. Consequently, involvement with a social media platform is expected to have a positive impact on attitudes towards advertisements on the platform. Hence, this study assumes that:

Hypothesis 5 (H5).

Involvement with Instagram positively influences Attitude towards Ads on Instagram.

2.3. Advertising Avoidance

Kelly et al. [16] define advertising avoidance as “any action that reduces exposure, or the ‘turning off’, to advertising” (p. 488). Advertising avoidance can have both a cognitive and behavioral nature [15], cognitive avoidance is not paying attention to ads, and behavioral avoidance implies actions such as closing an ad display or mechanically block all advertisements. Particularly on social media platforms, advertising avoidance is justified by the lack of benefit and pleasure that consumers might perceive in advertising [16], the fact that excessive exposure to this type of stimuli generates consumer irritation [29], and the perceived intrusiveness and threat to users’ freedom [15]. Additionally, perceived relevance of the advertisements is pointed out as a major trigger of advertising engagement [16,30]. However, social media also facilitates the association of referrals with advertising [16], which in turn enhances two of the most relevant triggers of online advertising engagement: relevance and authenticity.

The literature highlights that contextual factors, including those related to the digital platform, are associated with users’ avoidance of advertising [30]. As consumers become more familiar and engaged with social media, they are increasingly exposed to the inherent advertising mechanisms of these platforms. Voorveld et al. [27] stressed that consumers’ engagement with a social media platform influences their interaction with advertising within that platform. Schouten et al. [28] added that consumers with high involvement with social media platforms are more likely to accept advertisements within that type of platform. Consequently, one can infer that advertising avoidance is negatively affected by platform involvement, namely social media platforms. In line with these contributions, it is assumed that:

Hypothesis 6 (H6).

Involvement with Instagram has a negatively influences Advertising Avoidance.

Furthermore, extant literature also demonstrates that advertising avoidance is negatively associated with attitude towards ads on social media platforms [29]. A recent study by Chen et al. [31] explored consumer attitudes toward social media platforms in more depth. They explain that attitude toward social media platforms is an important factor to understand users’ behaviors, namely due to the use of personal data to guide personalized content and ads. Overall, the relevance of advertisements explains consumer perceptions and behaviors and determine attitudes toward social media platforms [31]. In particular, consumers that are more prone to reduce their exposure to advertising, either by cognitive or behavioral processes [15,16], are expected to have more negative evaluations of this type of communication. In line with these contributions that highlight the expected negative impacts of advertising avoidance on consumers’ attitudes towards advertising, including on social media platforms, it is assumed that:

Hypothesis 7 (H7).

Advertising Avoidance negatively influences Attitude towards Ads on Instagram.

2.4. Expected Effects of Attitude towards Advertising on Social Media Platforms

Petty and Cacioppo [13] define attitude as “general evaluations people hold in regard to themselves, other people, objects, and issues. These general evaluations can be based on a variety of behavioral, affective, and cognitive experiences, and are capable of influencing or guiding behavioral, affective, and cognitive processes” (p. 127). As such, attitude is an important antecedent of consumer behavior, frequently explored in influencer marketing literature [1,2].

The literature reveals that, despite being aware of their commercial endorsements, followers of digital influencers tend to hold positive evaluations of sponsored posts. This can be attributed to mechanisms such as positive bias towards the influencer and cross-validation of the information conveyed [32], along with the overall recognition of the influencers’ opinions and recommendations as valuable [27,32]. However, the effectiveness of advertisements on social media is shown to be dependent on the attitude toward the social media platform [33]. Indeed, consumers who hold more favorable attitudes towards the platform tend to perceive the ads as more relevant and respond more favorably to them [33]. In line with this, it is assumed that favorable attitudes towards advertising on social media platforms will favor the evaluations of digital influencers’ communication, acknowledging higher credibility levels. As an alternative persuasion process, digital influencer communication may benefit from a “halo effect” of attitudes related to the social media platform [33], namely in terms of perceived relevance. Therefore, as the literature indicates that consumers’ attitude towards advertising on social media platforms makes them more receptive to the messages posted by influencers, thereby enhancing the credibility ascribed to them, this study hypothesizes that:

Hypothesis 8 (H8).

Attitude Towards Ads in Instagram positively influences Instagrammer Credibility.

Overall, attitude towards advertising on social media platforms is shown as an important predictor of consumer responses [34], particularly purchase intentions [35,36]. As explained by Song and Kim [36], the relationship between attitude and intentions is well established in the communication literature. Moreover, the evidence of strong causal effects has been also confirmed in the influencer marketing realm [35,36,37], as the characteristics of digital influencers and the nature of the relationships established with their followers favor the effects on purchase intention. In line with these contributions that suggest that attitude toward advertising on social media platforms positively influences purchase intention, it is assumed that:

Hypothesis 9 (H9).

Attitude Towards Ads in Instagram positively influences Purchase Intention.

2.5. Expected Effect of Digital Influencers’ Credibility on Purchase Intention

The ELM posits that source credibility influences, at least in part, the persuasiveness of a message [13]. Moreover, source credibility is an essential factor for understanding consumer behavior, including purchase intentions [12]. This is particularly evident in the context of influencer marketing. The success of digital influencers, characterized by their reach and impact, depend on their perceived expertise, the level of intimacy they establish with their followers, and the authenticity of their communication [8]. Therefore, the source credibility of influencers emerges as a crucial factor explaining their ability to generate favorable outcomes for brands and products they endorse [2,8]. Masuda et al. [4] explains that, for instance, the perception of an influencer’s trustworthiness by followers positively influences their purchase intentions and ultimately leads to increased buying behavior. As a result, source credibility is consistently emphasized in influencer marketing research, with numerous studies demonstrating its positive and significant influence on the purchase intention of digital influencers’ followers (e.g., [4,28,38,39]), including for food products [9]. In line with these contributions, and considering that the credibility of digital influencers positively affects the purchase intention of the products they recommend, it is assumed that:

Hypothesis 10 (H10).

Instagrammer Credibility positively affects the Purchase Intention of the products they recommend.

Figure 1 outlines the set of hypotheses proposed for this study.

3. Method

This section presents the methodology employed in a quantitative study conducted to test the research model proposed in this article. The primary focus of this study centered on healthy food purchase intention within the context of influencer marketing, specifically Instagram. Digital influencers active on Instagram are referred to as ‘Instagrammers’ throughout these pages. As of early 2023, Instagram had over two billion active monthly users, making it one of the most successful social media platforms [40]. The platform’s content-sharing features, particularly for videos and images, have attracted celebrities and digital influencers, particularly in sectors such as beauty, fashion, tourism, and wellness. Instagram is widely recognized as one of the most utilized social media platforms by marketers [40]. Moreover, the majority of citizens in many Western countries, including Portugal where this study was conducted, are active Instagram users [41]. Considering these factors, Instagram was deemed an ideal platform for conducting this research.

3.1. Materials and Measurements

Data were collected online through a questionnaire comprising 36 five-point Likert-type questions, along with five questions concerning respondents’ profiles, including one filter question. Only individuals who acknowledged following at least one Instagrammer associated with healthy eating and lifestyle were eligible to participate and respond to the questionnaire.

The set of measurement scales was adapted from previous studies (See Appendix A). Consumer involvement with healthy food was evaluated using a five-point interval scale adapted from O’Cass [42], ranging from 1-completely disagree to 5-complete agree. Out of the 12 questions on the scale, four pertained to product involvement, four addressed consumption involvement, and the remaining four focused on involvement in the respondents’ decision-making process when purchasing foods perceived as healthy. Purchase Intention was assessed using three indicators of willingness to buy, borrowed from Dodds et al. [43]. Instagrammer credibility was measured by nine items adapted from Ohanian [12], with three items pertaining to Instagrammer Attractiveness, three to Instagrammer Expertise, and three to Instagrammer Trustworthiness. Involvement with Instagram was evaluated through seven questions adapted from Zaichkowsky [14], while the Attitude Towards Ads on Instagram was captured using three items adapted from Speck and Elliott [44]. Additionally, Advertising Avoidance was measured using three Likert-type questions adapted from Speck and Elliott [45].

The questionnaire underwent a pre-test involving 20 individuals who shared similar characteristics with the intended interviewees. These individuals confirmed the clarity of the instructions and the content of the questions.

The ethical principles commonly applied in social science research [46] were thoroughly taken into account. Participation in the study was voluntary, and the anonymity and confidentiality of the participants were ensured. No identifying or sensitive information was requested from the participants. Prior to their involvement, participants were provided with comprehensive information about the nature, objectives, and duration of the study. They were informed that the data they provided would be analyzed in an aggregated manner, and the results might be published. Participants were required to provide informed consent before participating by responding to the questionnaire.

3.2. Participants

The recruitment of participants followed a snowball sampling method, wherein one of the authors approached a total of 25 individuals from their social networks and requested them to share the invitation with ten individuals from their own networks. This process continued recursively. Only Instagram users who followed at least one influencer associated with healthy foods were eligible to complete the questionnaire. This methodology resulted in a sample comprising 221 valid responses, which met the minimum recommended sample size [47], namely considering that “one should strive for a sample size above 100, preferably above 200” (p. 29). Due to being a non-probability sampling method, and despite enabling the recruitment of a diversified set of participants in terms of age and education, it generated an unbalanced sample in terms of gender. The sample primarily consists of females (75%), as depicted in

Table 1. Participants’ characterization.

Gender
Female	156	74%
Male	55	26%
Age
<18 years	2	1%
18–22 years	64	30%
23–26 years	43	20%
27–30 years	27	13%
31–35 years	34	16%
36–40 years	24	11%
40+ years	27	13%
Education
Elementary School	82	39%
High School	4	2%
Higher Education	66	31%
Master, Ph.D.	69	33%

.

3.3. Analysis Procedures

The analysis was conducted in two stages. Firstly, the measurement model was analyzed using an Exploratory-Confirmatory Approach (E/CFA) to assess the adequacy, reliability, and validity of each factor. Secondly, the structural model was analyzed using Structural Equation Modeling (SEM) to examine the ten research hypotheses. The decision to employ E/CFA was based on the fact that all the factors had been previously tested in other studies. It is worth noting that according to Brown [48] “although underutilized in the applied literature, E/CFA can be a useful precursor to CFA, which allows the researcher to more fully explore measurement structures before moving on to a confirmatory structure” (p. 193).

4. Results

4.1. Measurement Model

The analysis of the measurement model confirmed the presence of eight first-order factors, namely Advertising Avoidance, Attitude Towards Ads on Instagram, Consumer Involvement with Healthy Foods, Instagrammer Attractiveness, Instagrammer Expertise, Instagrammer Trustworthiness, Involvement with Instagram, and Purchase Intention. All of these factors demonstrated reliability and validity. Among the 40 variables initially collected, five were deemed inappropriate for capturing the intended phenomenon and were therefore excluded. Furthermore, among the remaining 35 variables, 11 required reverse coding and were subsequently recoded as “_R”.

Table 2. Measurement model.

Items	Factors	Regression Weights	S.E.	p	Standardized Regression Weights
IA3_R	Instagrammer Attractiveness	1.000	-	-	0.732
IA1_R		1.160	0.101	0.000	0.812
IA2_R		1.230	0.103	0.000	0.902
IT3_R	Instagrammer Trustworthiness	1.000	-	-	0.955
IT2_R		0.971	0.029	0.000	0.966
IT1_R		0.948	0.043	0.000	0.869
IE3_R	Instagrammer Expertise	1.000	-	-	0.864
IE2_R		0.971	0.045	0.000	0.962
IE1_R		0.866	0.047	0.000	0.890
P11	Purchase Intention	1.000	-	-	0.884
P12		1.027	0.055	0.000	0.915
P13		0.975	0.057	0.000	0.856
CI1	Involvement with Healthy Food	1.000	-	-	0.907
CI10		0.898	0.055	0.000	0.794
CI11		1.014	0.048	0.000	0.887
CI2		0.995	0.043	0.000	0.920
CI3		0.989	0.045	0.000	0.905
CI4		0.986	0.045	0.000	0.904
CI5		1.002	0.045	0.000	0.905
CI6		0.994	0.041	0.000	0.933
CI7		0.970	0.052	0.000	0.846
CI8		1.016	0.044	0.000	0.917
CI9		1.037	0.045	0.000	0.920
AA3	Advertising Avoidance	1.000	-	-	0.882
AA2		1.004	0.062	0.000	0.912
AA1		0.742	0.060	0.000	0.720
IWI7_R	Involvement with Instagram	1.000	-	-	0.509
IWI6		1.471	0.200	0.000	0.773
IWI5		1.606	0.214	0.000	0.808
IWI3		1.628	0.217	0.000	0.807
IWI2		1.596	0.216	0.000	0.781
IWI1_R		1.313	0.195	0.000	0.645
ATAI3	Attitude Towards Ads on Instagram	1.000	-	-	0.637
ATAI2		1.734	0.159	0.000	0.916
ATAI1		1.792	0.164	0.000	0.940

presents the factors along with their original and standardized indicators, as well as the corresponding standard errors and p-values.

All of the identified dimensions exhibited Composite Reliability (CR) and MaxR(H) values exceeding the minimum expected threshold of 0.7 [49]. Additionally, the Average Variance Extracted (AVE) indices were above 0.5 [47], indicating satisfactory reliability and convergent validity of the factors (

Table 3. Factors’ reliability and Average Variance Extracted (AVE).

Factors	CR	AVE	MaxR(H)
Involvement with Instagram (a)	0.869	0.531	0.887
Instagrammer Attractiveness (b)	0.858	0.670	0.882
Instagrammer Trustworthiness (c)	0.951	0.867	0.965
Instagrammer Expertise (d)	0.932	0.821	0.950
Purchase Intention (e)	0.916	0.784	0.920
Involvement with Healthy Food (f)	0.978	0.801	0.980
Advertising Avoidance (g)	0.879	0.709	0.905
Attitude Towards Ads on Instagram (h)	0.877	0.709	0.931

). The measurement model demonstrated favorable overall fit indices, with the Comparative Fit Index (CFI) at 0.931, Tucker-Lewis Index (TLI) at 0.923, Incremental Fit Index (IFI) at 0.932, Root Mean Square Error of Approximation (RMSEA) at 0.066, and CMIN/DF at 1.966.

Discriminant validity was evaluated using the criterion proposed by Fornell and Larcker [50], which compares the correlations between factors with the square roots of their respective Average Variance Extracted (AVE) values. According to this criterion, discriminant validity is established when the square root of each AVE value is greater than the correlation coefficients between the factor in question and all other factors. As depicted in

Table 4. Factors’ correlations (for discriminant validity analysis).

Factor	(a)	(b)	(c)	(d)	(e)	(f)	(g)	(h)
(a)	0.729
(b)	0.282	0.818
(c)	0.258	0.422	0.931
(d)	0.349	0.344	0.847	0.906
(e)	0.265	0.062	0.374	0.393	0.885
(f)	0.012	0.105	0.153	0.103	0.293	0.895
(g)	−0.148	0.172	−0.023	−0.034	−0.072	0.347	0.842
(h)	0.330	0.133	0.063	0.088	0.351	0.191	−0.204	0.842

Notes: (a) = Involvement with Instagram; (b) = Instagrammer Attractiveness; (c) = Instagrammer Trustworthiness; (d) = Instagrammer Expertise; (e) = Purchase Intention; (f) = Involvement with Healthy Food; (g) = Advertising Avoidance; (h) = Attitude Towards Ads on Instagram. The values on the main diagonal, printed in bold, correspond to the square root of the AVEs.

, the square roots of the AVE values, on the main diagonal, surpass the correlations observed in the corresponding rows and columns, indicating the presence of discriminant validity.

4.2. Structural Model and Test of Hypotheses

Like previous studies (e.g., [9,18]), this study also considers the credibility of Instagrammers as a second-order construct. Although the first-order model (omitted for brevity) presents challenges in interpretation and complexity, it exhibited a significantly lower level of parsimony (CMIN/GL = 2.406) compared to the adopted second-order model (CMIN/GL = 1.986), making the latter a more preferable choice. Hence, similar to the measurement model, the structural model that incorporates Instagrammers’ credibility as a second-order factor demonstrates favorable fit indices (CFI = 0.928; TLI = 0.928; IFI = 0.921; RMSEA = 0.067; CMIN/DF = 1.966), indicating its suitability for interpreting the phenomenon. The results of the study confirm the significance of all three dimensions of the Ohanian scale [12] in reflecting the credibility of Instagrammers, particularly expertise and trustworthiness, which are identified as the most important factors.

According to the findings, consumer involvement with healthy eating, despite other influential factors to be discussed later, significantly impacts the intention to purchase healthy food, thereby confirming hypothesis H1. It is also confirmed that involvement with healthy eating significantly reinforces advertising avoidance (H2) and the attitude toward ads on Instagram (H3).

Conversely, consumer engagement with Instagram strengthens both Instagrammers’ credibility and the attitude toward ads on the social platform, providing confirmation for hypotheses H4 and H5, while simultaneously reducing aversion to advertising, confirming hypothesis H6. Additionally, advertising aversion significantly diminishes favorable attitudes toward ads on Instagram, validating hypothesis H7.

The attitude toward advertising on Instagram directly contributes significantly to purchase intention, thereby confirming hypothesis H9. However, the expected influence of this attitude on Instagrammers’ credibility (H8) was not confirmed. As anticipated, the credibility of recommenders strongly and decisively impacts (36.5%) the intention to purchase food perceived as healthy, thus supporting hypothesis H10.

Table 5. Structural relationships in the model.

Endogenous Factors	Hypotheses	Exogenous Factors	Unstandardized Regression Weights	S.E.	C.R.	p	Standardized Regression Weights
Purchase Intention	H1	Involvement with Healthy Food	0.189	0.062	3.08	0.002	0.195
Advertising Avoidance	H2	Consumer Involvement with Healthy Food	0.358	0.071	5.07	0.000	0.350
Attitude Towards Ads on Instagram	H3	Involvement with Healthy Food	0.143	0.038	3.76	0.000	0.277
Instagrammer Credibility	H4	Involvement with Instagram	0.170	0.052	3.23	0.001	0.349
Attitude Towards Ads on Instagram	H5	Involvement with Instagram	0.227	0.063	3.58	0.000	0.288
Advertising Avoidance	H6	Involvement with Instagram	−0.240	0.114	−2.11	0.035	−0.153
Attitude Towards Ads on Instagram	H7	Advertising Avoidance	−0.131	0.039	−3.39	0.000	−0.261
Instagrammer Credibility	H8	Attitude Towards Ads on Instagram	−0.015	0.046	−0.33	0.743	−0.025
Purchase Intention	H9	Attitude Towards Ads on Instagram	0.542	0.131	4.13	0.000	0.288
Purchase Intention	H10	Instagrammer Credibility	1.116	0.285	3.91	0.000	0.365

Notes: S.E. = Standard Error; C.R. (Critical Ratio) = t-value.

summarizes the structural relationships relating to the hypotheses tested, with the associated statistics.

5. Discussion

One main aim of the current study is investigating consumers purchase intention of healthy foods in the context of influencer marketing. The findings corroborated that purchase intention of healthy foods is positively influenced by digital influencer perceived credibility, involvement with healthy foods, and attitude toward advertising on Instagram.

Involvement with healthy foods was found to have a positive impact on purchase intention, supporting previous studies conducted in the field of influencer marketing (Hypothesis H1). However, it is important to note that the study by Cabeza-Ramirez et al. [25] did not support this hypothesis. Therefore, the present study reopens the discussion on the effects of product involvement on followers of digital influencers and provides additional support to existing literature that examines the relationship between product involvement and consumer behavior (e.g., [19,23,24]). Additionally, the positive impact of attitude toward advertising on Instagram on purchase intention (Hypothesis H9) was supported by our study, aligning with previous research conducted in the context of digital influencers (e.g., [35,36,37]). Thus, our study confirms the established research tradition that recognizes attitude as a key determinant of purchase intentions. As for the effect of digital influencer credibility, since Ohanian’s seminal work [12], there has been a consensus in persuasion studies regarding the positive effect of source credibility on consumer behavior, particularly in terms of purchase intention. Our study confirms that the credibility of digital influencers positively influences purchase intention (Hypothesis H10), specifically in the context of healthy foods on Instagram, in line with findings from other studies on food products [9] and the extensive literature on influencer marketing exploring consumers’ purchase intentions (e.g., [4,28,38,39]).

The current study also hypothesized antecedent relationships of advertising avoidance and attitudes. Corroborating the assumptions made, it was confirmed that involvement with healthy foods and involvement with Instagram affect advertising avoidance behavior, and that these three constructs affect attitude toward advertising on Instagram.

Involvement with healthy foods was found to have a positive relationship with advertising avoidance (Hypothesis H2), supporting the theoretical framework proposed ELM [13]. This study also confirmed the positive relationship between product involvement and attitude towards advertising on Instagram (Hypothesis H3), aligning with the findings of Cabeza-Ramirez et al. [25]. These results also support previous studies that emphasize the link between product involvement and consumer attitudes (e.g., [21,24,26]).

Involvement with the social media platform, was found to enhance the credibility attributed to digital influencers on the platform (Hypothesis H4), further supporting the findings of other authors [27,28]. Additionally, involvement with Instagram was positively associated with attitudes towards advertisements on the platform (Hypothesis H5), aligning with the inferences drawn from the findings of Voorveld et al. [27]. This study also hypothesized that involvement with Instagram reduces advertising avoidance (Hypothesis H6). This hypothesis was confirmed in the context of Instagram, aligning with indications from existing literature [28,30].

As anticipated, a negative association was observed between advertising avoidance and attitude towards advertising on social media platforms, providing support for the proposed hypothesis (Hypothesis H7) and aligning with findings from previous studies (e.g., [29]). However, the expected relationship between consumers’ attitude towards advertising on social media platforms and digital influencer credibility (Hypothesis H8) was not supported by this study, contradicting cues from previous research that suggested a “halo effect” [33] from attitudes, which we assumed extended to source credibility. One possible explanation for this could be the critical role of the chosen product in consumers’ health and well-being. Consequently, the content shared by influencers is expected to be perceived as extremely valuable [27,32]. Additionally, the fact that participants in the study were only active social media users who followed at least one digital influencer positioned as an expert in healthy food might contribute to mitigating the variance between attitudes towards advertising and perceived influencer credibility.

In conclusion, the study confirms that credibility of Instagrammers can influence purchase intention. Moreover, the results indicate that a positive attitude toward advertising on Instagram enhances purchase intention but does not directly affect the perceived credibility of influencers. The study emphasizes the importance of considering the consumer’s involvement with both the platform and the recommended product. Involvement with the product and with the platform itself are key factors in understanding influencer marketing.

6. Conclusions

This article examines the influence of digital influencers on Instagram and their impact on consumer purchase intentions for healthy food. This study combines the theories of source credibility and the elaboration likelihood model to further explain consumer purchase intentions in the context of digital influencers, specifically regarding healthy food. It explores how the credibility of Instagram influencers intersects with consumers’ attitudes towards advertising, involvement with healthy foods, involvement with Instagram, and advertising avoidance. In addressing the proposed research question, the findings demonstrate that digital influencers have a positive impact on healthy food purchase intention through their credibility. Additionally, consumers’ involvement with healthy food and their attitudes towards advertisements also play a significant role in influencing purchase intention positively. Furthermore, consumers’ involvement with Instagram reinforces influencers’ credibility and reduces advertising avoidance. Both advertising avoidance and consumer engagement with healthy food exert significant influences on attitudes towards ads on Instagram, ultimately enhancing purchase intention. To the best of the authors’ knowledge, this is the first study to provide a comprehensive view of these influences.

The findings contribute to the literature on persuasion, influencer marketing, and product involvement, offering valuable insights in these research areas. These contributions help to fill a relevant research gap in the literature, which has insufficient understanding of the influencer marketing phenomenon regarding the health and wellness industry. As noted in the previous sections, this is a particularly relevant sector not only for its growth but also for the importance of healthier consumer behaviors for well-being and for overall sustainable development. The model developed for this study is one of its contributions, which may be adapted to other contexts, including different types of digital influencers, different social media platforms, and other product categories. The combination of the two theories, TSC and ELM, is not frequent in digital influencer literature. However, this study demonstrates that it can provide a wider understanding of the phenomenon, given the complementarity of the perspectives, and the interdependence of its constructs. In particular, the combination of consumer involvement, inspired by ELM, with source credibility, borrowed from TSC, enables further understanding of persuasiveness. This perspective can be adopted by future research on consumer behavior.

This study also provides valuable managerial insights for social media and brand managers and marketers, aiding them in making informed decisions and enhancing their understanding of digital influencer marketing’s effectiveness. Managers are often faced with decisions on communication budgets, media selection, and targeting strategies. By understanding the significance of involvement with Instagram in shaping attitudes and its influence on purchase intentions, managers can make informed decisions regarding the use of influencers. In some cases, investing in shaping favorable attitudes towards the product may yield greater rewards than relying solely on influencer support, irrespective of their perceived credibility. This highlights the importance of considering the broader context and objectives when allocating communication resources.

The main constraint of this research pertains to the sample characteristics. While the sample did not exhibit significant deviations from normality, it is important to acknowledge that the non-probabilistic sampling method limits the generalizability of the findings beyond the sample itself. Particularly, this sample was unbalanced in terms of gender, as the majority of participants were female. Additionally, the sample size (n = 211) did not allow for certain analyses that would be desirable in this case, such as multi-group analyses. Therefore, further studies on the same topic are highly recommended, preferably using larger probabilistic samples, either to replicate the model in other social media platforms or to test the invariance of the identified relationships among groups with high and low involvement with healthy food and the social media platform itself.

In order to extend our knowledge about the effectiveness of influencer marketing, future research should explore additional factors that may explain consumers’ outcomes, as recommended by extant literature [1,2,3]. ELM offers several future research opportunities. In particular, and as noted by Petty and Cacioppo [13], recipient and context factors can play a determinant role in understanding the persuasiveness of messages beyond the impacts of source characteristics. Hence, future research can consider environmental cues such as the physical environment where the message is received, as well as considering the role of cultural, emotional, and social contexts to explain consumer outcomes of influencer marketing strategies.