The Evidence-Based Instrument for the Nutritional Assessment of Individuals with Autism Spectrum Disorder

Abstract

Background: Autism spectrum disorder (ASD) presents diverse challenges that significantly impact feeding, nutrition, growth, and development. The heterogeneity of ASD manifestations adds complexity to assessments due to the broad range of factors to be considered. Moreover, the literature lacks a comprehensive tool specifically addressing nutritional aspects in ASD. Methods: Conducted in two steps, this study first involved researchers selecting evidence-based elements related to ASD and nutrition to develop a preliminary tool. Content validation was subsequently undertaken using a modified Delphi method, whereby expert consensus was sought from 30 dietitians with experience in ASD, who evaluated the tool through a digital questionnaire. Four quality criteria were evaluated: functionality, organization, language and comprehensibility, and comprehensiveness. Results: Levels of strong agreement with the quality criteria ranged from 63.3% to 80%, specifically functionality (76.7%), organization (73.3%), language and comprehensibility (80%), and comprehensiveness (63.3%). Thematic analysis highlighted six key areas for improvement. The instrument assesses nutritional aspects across seven domains: life history, food-related aspects, feeding behavior, dietary intake, daily routines, clinical aspects, and anthropometry. Conclusions: This is the first known tool to comprehensively address the nutritional needs of individuals with ASD, offering a detailed framework for clinical application. It supports initial assessments, ongoing monitoring, and targeted interventions, supporting dietitians worldwide in clinical decision-making.

1. Introduction

Autism spectrum disorder (ASD) has shown an increasing prevalence over time [1,2]. Commonly referred to as autism, ASD is classified as a neurodevelopmental condition [3]. It is characterized by challenges in communication and social interaction, restricted and repetitive behaviors, as well as sensory and motor alterations that vary in intensity. These manifestations are present from early childhood, although they may be identified later in life [4]. Individuals with ASD may face various difficulties, leading to diverse phenotypes and distinct developmental trajectories [3,5]. In addition to core symptoms, co-occurring conditions are frequently observed, significantly impacting the quality of life [6,7]. Among these challenges, feeding difficulties stand out as a significant concern, as they can be exacerbated by autism characteristics, impaired skills, associated health conditions, comorbidities, and medical treatments, significantly affecting nutrition [8,9,10].

Recently, the term “pediatric feeding disorder” was proposed to unify diagnostic criteria, characterized by impaired and age-inappropriate food intake, and associated with medical and nutritional circumstances, feeding skills, and psychosocial dysfunction, including neurodevelopmental conditions like autism [11]. The prevalence of feeding problems in children with ASD is estimated at 46% to 90% [8,12,13]. These issues may manifest as persistent refusal to consume certain foods, difficulty in achieving sufficient intake to support healthy growth and development, and fear or aversion toward trying new or unfamiliar foods—known as food neophobia—which may arise from both behavioral and organic factors [14,15]. Furthermore, motor impairments associated with autism can contribute to feeding difficulties, including problems with chewing and swallowing, as well as challenges in properly handling utensils [16,17,18]. Emotional challenges and internalizing symptoms related to autism can lead to both overfeeding and underfeeding [19,20]. Similarly, when pharmacological intervention becomes necessary, potential metabolic and hormonal changes may further influence the mechanisms that regulate hunger and satiety [21,22,23].

These feeding-related challenges are a significant source of concern for parents regarding their children’s nutrition [14,24]. Parental stress has been positively associated with behavioral feeding issues, such as food refusal and rigidity, in autistic children [25]. Maternal anxiety has also been correlated with children’s feeding difficulties. In some cases, when coupled with less effective coping strategies, this may contribute to the persistence of disruptive feeding behaviors in autistic children [26,27]. Food selectivity can also affect the eating habits of other family members, contribute to increased marital stress among parents [28], and lead to social isolation in families with autistic children [12].

Food selectivity is the most frequently reported feeding issue in ASD [29] and has been defined as rejecting over 33% of offered foods or consuming fewer than 50 distinct foods per year [30]. When associated with autism, food selectivity often reflects preferences based on sensory characteristics, such as type, texture, or presentation [31].

Individuals with ASD and oral hypersensitivity face greater challenges with food acceptance compared to those without this trait [32]. They may also show a preference for specific brands and packaging [13,33], often favoring hyper-palatable foods like fast food and ultra-processed products, which are nutritionally imbalanced [34]. A tendency to refuse fruits and vegetables is also common [8,29], contributing to diets with a high intake of energy-dense, nutrient-poor foods and potential macro and micronutrient imbalances, increasing nutritional risks [35]. Food refusal is also linked to altered perception, inflexibility, and challenging behaviors associated with autism [30].

Children with ASD and food selectivity often exhibit behavioral issues such as screaming, crying, and aggression toward caregivers [29,36]. They may also establish meal rituals, including specific food presentation, utensil use, and rigid intake patterns [13]. Feeding problems, such as lack of appetite or inappropriate feeding behavior, can emerge in early childhood [37] and, if untreated, may persist or evolve during adolescence [38,39], continuing into adulthood [40] and potentially leading to health issues due to dysfunctional intake [41,42,43]. Individualized interventions influence the course of these issues [29].

Nutrition is a complex topic in the context of autism. In addition to feeding challenges, individuals with ASD are at increased risk for nutritional imbalances compared to neurotypical peers [8]. A meta-analysis reported significantly lower intakes of several nutrients among children with ASD, including calcium, vitamin D, and omega-3 fatty acids. The notably insufficient intake of calcium and vitamin D raises concerns regarding bone health and immune function. Although children with ASD also consumed less protein, phosphorus, selenium, thiamine, riboflavin, and vitamin B12 than typically developing children, their intake of these nutrients generally remained adequate or exceeded dietary recommendations [44]. However, when dietary intake becomes insufficient, the prescription of supplements becomes necessary to ensure that nutritional requirements are met [11].

Severe and chronic feeding problems are associated with a broad range of medical complications, including malnutrition, which can hinder growth and development and contribute to psychosocial and academic challenges. In extreme cases, invasive interventions such as enteral feeding may become necessary. Therefore, the routine assessment of pediatric feeding disorders should be an integral part of care in pediatric settings that serve individuals with ASD [8].

To address gaps in the nutritional assessment of individuals with ASD, it is crucial to explore strategies that consider each person’s family and cultural context, as well as etiological factors of feeding and nutritional problems, to develop appropriate interventions [36,45,46]. Studies have shown benefits in conditions associated with autism when individuals receive nutritional treatment [47,48], provided they are under professional clinical supervision [49,50].

Effective clinical practice requires a comprehensive assessment process, which must be rigorously validated and interpreted to accurately determine an individual’s nutritional status. This requires the use of specialized instruments designed to address nutrition-related issues [51]. However, the literature lacks a comprehensive tool capable of adequately capturing the diverse and heterogeneous characteristics of autism that significantly impact feeding and nutrition.

Given that accurate assessment is critical to tailor individualized clinical strategies, the aim of this study was to develop an evidence-based nutritional assessment instrument specifically designed for individuals with ASD. The tool was structured to integrate research and clinical practice by incorporating multiple indicators across clinical, behavioral, physiological, socioeconomic, and feeding domains that may impact nutrition in this population. Rather than focusing exclusively on nutritional status or feeding-related behavioral challenges, the instrument was designed to provide a comprehensive assessment of the individual’s overall nutritional profile, addressing the multifactorial nature of nutritional issues in ASD.

Recognizing the absence of a comprehensive, gold-standard, evidence-based nutritional assessment tool specific to ASD, this study also included a content validation phase. This phase was conducted through expert consensus using a modified Delphi method, a structured and iterative technique widely applied in healthcare research for the development and refinement of clinical instruments, especially in fields where empirical evidence remains limited. Thirty dietitians with expertise in ASD participated in this process, contributing to the refinement of the tool and ensuring its relevance and applicability.

By addressing key dimensions such as behavioral rigidity, gastrointestinal symptoms, and environmental and social conditions, the instrument aims to support clinicians, including those with limited experience in ASD, in performing thorough and individualized assessments. This integrated approach is intended to guide evidence-based interventions and help fill the existing gap in clinical practice regarding the nutritional assessment of individuals with ASD.

2. Materials and Methods

This study aims to develop an evidence-based instrument for the nutritional assessment of individuals with ASD. This descriptive and cross-sectional study combined quantitative and qualitative methods, divided into two steps: (1) development of the instrument and (2) refinement and content validation of the instrument, based on experts’ appraisals, utilizing a modified Delphi method in conjunction with a thematic analysis.

2.1. Step 1: Development and Structuring of the Initial Instrument Version

Based on the clinical and inquiry expertise of the researchers, an investigation of evidence-based studies was conducted to develop the initial version of the instrument. This preliminary version was organized into seven domains: clinical aspects, daily routines, life history, food-related aspects, feeding behavior, dietary intake, and anthropometry. Additionally, validated tools: the Bristol Stool Scale [52,53], the Brussels Infant and Toddler Stool Scale (BITSS) [54], the food diary [55], and anthropometric measurements [56,57] were incorporated. Supporting evidence and details underpinning its creation can be found in the Supplementary Material (Autism Nutritional Assessment (ANA): available in English, Portuguese, and French, with supporting documentation [3,4,5,7,8,9,11,12,13,17,18,19,28,30,31,36,37,43,45,46,47,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161]).

2.2. Step 2: Refinement of the Instrument

Selection of experts: A purposive sampling technique [162] was employed by disseminating the research invitation with specific participation criteria, targeting nutritionists experienced in ASD. The Dietitian Boards of Brazil and the researchers disclosed the invitation via social media and e-mail and later recruited the experts. Participants signed the Informed Consent Form and the Confidentiality Agreement and completed a profile questionnaire to characterize the sample. This approach led to the grouping of 30 expert dietitians from across the country, with a median of two years of clinical experience in providing care to individuals with ASD. The range of expertise varied, with a minimum of 1 year and a maximum of 10 years.

Appraisal of the instrument by experts using a modified Delphi method: After the sample was selected and characterized, each participant was invited to review the initial version of the instrument and appraise it using a digital questionnaire designed to gather their feedback. This variation of the Delphi method [163] facilitated the process and enabled the collection of opinions and recommendations of professionals [163,164].

The modified Delphi method was conducted via a structured digital form to appraise four quality criteria of the instrument: functionality, organization, language and comprehensibility, and comprehensiveness. These criteria were assessed using a 5-point Likert scale ranging from 1 (Strongly Disagree) to 5 (Strongly Agree) and included the following questions:

• Functionality: “The purpose of the instrument is to conduct a nutritional assessment of individuals with ASD. Do you agree that the instrument performs this with excellence?”
• Organization: “The instrument covers seven domains in the following ordinal presentation: clinical aspects, daily routines, life history, food-related aspects, feeding behavior, food intake, and anthropometry. Do you agree that these domains are appropriately presented in the instrument?”
• Language and comprehensibility: “Do you agree that the language used in the instrument is clear and understandable, without requiring further examples or explanations?”
• Comprehensiveness: “Do you agree that the instrument addresses all relevant nutrition aspects for individuals with ASD?”

In addition to these questions, optional open-ended questions solicited recommendations for further refinement of the instrument. To assess the relationship between quality criteria scores and experience with ASD, a two-year cutoff was established to differentiate dietitians with up to two years of experience from those with over two years of experience. Figure 1 shows the flowchart of the instrument’s refinement process.

2.3. Data Analysis

The four quality criteria for appraising the instrument developed in this study are functionality, organization, language and comprehensibility, and comprehensiveness. These aspects were described using frequency, means, and standard deviations (SD). Fisher’s exact and linear association tests were applied to demonstrate the association between the expert’s experience and the appraisal of the quality criteria. The analysis was performed using IBM SPSS Statistics v. 30 for Windows [165]. Experts’ recommendations were analyzed using thematic analysis [166,167]. This approach enabled a deeper understanding of each expert’s perceptions, contributing to the content validation and refinement of the instrument.

3. Results

An initial version of the evidence-based nutritional assessment instrument was developed, incorporating ASD- and nutrition-related factors identified in previous studies, which were recorded in supporting documentation.

The experts’ appraisal was based on four quality criteria using the modified Delphi method. Regarding the functionality criterion, which evaluates whether the instrument accurately and excellently provides a comprehensive nutritional assessment of individuals with ASD, the mean level of agreement was 4.73 (SD = 0.52), with 76.7% of the sample strongly agreeing. In the ‘organization’ criterion, which stated the adequacy of the ordinal presentation of domains within the instrument, the mean level of agreement was 4.50 (SD = 1.07), with 73.3% strongly agreeing. For the ‘language and comprehensibility’ criterion, which examines whether the instrument uses clear and understandable language, the level of agreement was 4.77 (SD = 0.50), with 80% strongly agreeing. As for comprehensiveness, which assesses whether the instrument covers all relevant nutritional aspects in the context of ASD, the mean level of agreement was 4.60 (SD = 0.56), with 63.3% of the sample strongly agreeing.

Scores for the quality criteria were analyzed to determine their association with experience in ASD, using a cutoff of two years to distinguish professionals with up to two years of experience from those with more than two years. It was observed that the latter gave lower scores for the comprehensiveness criterion, according to Fisher’s exact test (p-value = 0.018) and the linear association test (p-value = 0.011). No significant associations were observed for the other quality criteria.

Following 26 recommendations by the experts, the thematic analysis was converted into six categories, with the number of recommendations in each shown in parentheses: sensory system (n = 6), socialization (n = 2), biochemical markers (n = 5), food selectivity (n = 7), feeding behavior (n = 3), and organization (n = 3). Based on these analyses, the authors critically evaluated the experts’ recommendations and refined the instrument accordingly. This included forming a subdomain on sensory issues related to food within the food-related aspects domain, consisting of eight questions to assess sensory influences on feeding. A question regarding the impact of socialization difficulties in celebratory and/or school contexts involving food was added to the feeding behavior domain. Additionally, two questions regarding restricted interests or behavioral inflexibility in autism, particularly the need for specific places and utensils during meals, were included in this domain. A subdomain on biochemical markers for nutritional assessment was added to the clinical aspects domain. Two questions about food selectivity were added, enabling parent/caregiver perceptions, which can be analyzed in conjunction with other questions in the instrument. Moreover, recommendations for changing the order of domain presentations were implemented. After the identification section, the final sequence of domains was as follows: life history, food-related aspects, feeding behavior, dietary intake, daily routines, clinical aspects, and anthropometry.

Table 1. Results of Thematic Analysis of Experts’ Recommendations for the Instrument’s Refinement.

Theme	Experts’ Recommendations	Preliminary Version of the Instrument	Refinement Adjustments Implemented
Sensory system	I suggest further exploring sensory issues in the questionnaire. Ask if there is any aversion to certain foods. Which foods have been tried? Which foods have never been tried, and is this due to their smell, texture, or color? Add information about sensations, such as preferences for certain flavors, textures, and temperatures. Whether there is sensitivity to food temperature. Further explore food colors and textures. Include information about preferred textures and what sensations the patient cannot tolerate (such as the smell of eggs).	An open-ended question to capture the caregiver’s perception of the individual’s food preferences based on specific textures or colors.	A subdomain of sensory issues was formed within the domain of food-related aspects. It includes seven questions regarding textures, appearances, smells, tastes, food temperature, and utensils.
Socialization	Include socialization. To what extent does food interfere with these moments? Monitor the patients’ social issues. Understand how celebratory days and school events are managed, and ensure that feeding difficulties do not become an additional problem by creating suggestions for these occasions.	The instrument did not directly address socialization in the context of feeding.	A question about the influence of socialization on feeding was added to the feeding behavior domain.
Biochemical markers	Additional section for biochemical testing. Include the biochemical testing. Add space for biochemical tests. Ask for recent laboratory tests. If the individual has a history of anemia.	The instrument did not directly address this issue.	A subdomain was inserted within the Clinical aspects domain to address biochemical markers related to nutritional evaluation.
Food selectivity	Some mothers report that children accept certain foods better until a certain age. I always ask when this happened and if anything occurred around that time. There could have been some trauma (such as canker sores, laryngitis, or viral infections). Include a question asking when food-related complaints or difficulties were first identified. Include a question asking at what age food selectivity begins. When did the food selectivity begin? I would address additional issues beyond these, such as exploring food selectivity within the context of autism. Foods and liquids the child used to consume but now refuses. I noticed there was no question related to food selectivity.	The instrument did not directly address this issue.	A question requesting details about food selectivity was added to the feeding behavior domain.
Feeding behavior	Could you add the location where the child eats? In addition to referencing the high chair, ask about the environment where the individual eats. It would be interesting to investigate the use of preferred objects for feeding as well (such as cups or plates).	The instrument did not directly address this issue.	Questions were included regarding the usual place where meals are eaten and the preferred utensils in the feeding behavior domain.
Organization	I would change the order to Identification, History, Diet, Routine, and Clinical aspects. Anamnesis is usually our first contact with the family; many are still grieving the diagnosis and in the process of acceptance. Listening to the history before asking about the autism diagnosis helps build rapport with the family and improves the quality of open-ended responses. Since this is a nutritional assessment tool and considering practical aspects of nutritional care, I believe that parents often begin their ponderings on diet aspects. It would be useful to place diet-related items earlier in the questionnaire. The section on pregnancy should be placed at the beginning, as the patient starts by discussing this topic before moving on to feeding.	The arrangement of the domains was as follows: identification, clinical aspects, daily routine, life history, food-related aspects, feeding behavior, dietary intake, and anthropometry.	The domains were structured in a specific chronology, making it easier for the caregiver to respond. The final domains were adjusted to include identification, life history, food-related aspects, feeding behavior, dietary intake, daily routines, clinical aspects, and anthropometry.

details the experts’ recommendations, along with the corresponding themes and refinement actions. The complete final version is accompanied by supporting documentation and application instructions, provided in three languages (Supplementary Material).

4. Discussion

From 2014 to 2024, the number of publications in PubMed alone exploring the relationship between nutrition and autism increased by approximately 422%, reflecting the growing interest in understanding how dietary factors may influence the development and management of ASD. Researchers are increasingly exploring various nutritional interventions and their potential impacts, contributing to a better understanding of this complex condition. However, much of this information remains largely unstandardized and not synthesized, which can hinder its specific use in nutritional assessments for this population. To our knowledge, there are currently no available questionnaires in the literature that comprehensively assess different nutritional aspects in a single instrument unique to individuals with ASD. Some tools exist for other populations, such as individuals with Avoidant/Restrictive Food Intake Disorder (ARFID) [168], kidney disease [169], pediatric oncology patients [170], children living with human immunodeficiency virus [171], childhood obesity [172], and even the school context [173]. Nevertheless, these instruments are not suitable for individuals with ASD due to the heterogeneous and complex nature of the condition.

In this study, the refined version of the instrument was developed based on expert recommendations and encompasses seven domains: life history, food-related aspects, feeding behavior, dietary intake, daily routines, clinical aspects, and anthropometry. These domains reflect the comprehensive approach needed to adequately evaluate the diverse factors that may influence the nutrition of individuals with ASD. Each domain is discussed in detail, including the rationale for the inclusion of specific items, thereby offering a structured framework to support the tool’s use in clinical practice.

A comprehensive assessment must consider autism characteristics that directly influence skills and competencies related to proper feeding and nutrition, as well as the recognized health conditions and potential challenges associated with ASD, to ensure the healthy development and growth [8].

Life History: This domain is designed to explore prenatal, perinatal, and familial factors that may influence nutritional development. It emphasizes the collection of a detailed developmental history, including both genetic and environmental influences. The domain comprehensively considers the individual’s social context, early development, and family dynamics, elements that are essential for understanding the environmental and relational factors that may affect nutritional status and feeding behaviors in individuals with ASD. It involves gathering information to explore potential genetic influences on health, with inquiries into the health of siblings and parents, as well as data from the pre- and perinatal periods. Inherited genes and environmental factors are important, as they can influence metabolic and immunological health and may be modified by exposure to certain agents, such as nutrition and maternal behaviors. The impact of these influences is particularly significant during the ‘1000 days’ period, which spans from preconception, through pregnancy, into the early years of an individual’s life, operating via epigenetic mechanisms [174,175]. Additionally, some of these factors may increase the likelihood of ASD, such as the mother’s health conditions, events during gestation [176], and factors like prematurity and low or high birth weight [3].

Food-Related Aspects: This domain includes questions from the earliest stages of childhood. Initially centered on breastfeeding and complementary feeding practices, it was expanded to address a broader range of food-related factors, such as the introduction of solid foods, food intolerances, adherence to restrictive diets, use of dietary supplements, and the impact of sensory characteristics on feeding. Based on expert recommendations, items related to sensory experiences, such as texture, temperature, and food aversions, were added, resulting in the development of a dedicated subdomain focused specifically on sensory influences.

Atypical responses to sensory stimuli have recently been included in the diagnostic criteria for ASD [66]. It is estimated that these sensory processing alterations reach 74% of children with autism, manifesting in various ways, such as over-responsiveness, characterized by extreme sensitivity; diminished responsiveness, with little or no reaction to stimuli such as touch or pain; and sensory-seeking behaviors, where the individual actively pursues new sensations [177]. Sensory dysregulation significantly contributes to feeding challenges in individuals with ASD, emphasizing the need to assess their sensory profiles for tailored interventions [142,178]. Hypersensitivity often leads to avoiding foods due to their appearance, texture, smell, or consistency, resulting in selective eating. Hyposensitivity is associated with a preference for intense flavors, difficulty identifying strong odors, messy eating, or retaining food in the mouth. Sensory-seeking behavior includes mouthing objects or licking surfaces for new sensory experiences [179]. To identify each individual’s sensory profile, consulting with professionals from the care team, particularly the occupational therapist, may be necessary, as they are typically responsible for addressing sensory system needs.

Feeding Behavior: In accordance with expert recommendations, this domain was expanded to include additional questions regarding the usual location of meals, preferred utensils used during feeding, more detailed items for identifying food selectivity, and aspects of social interaction during mealtimes. Overall, the domain focuses on examining eating habits and behaviors during meals, as well as caregivers’ perceptions and concerns related to their children’s feeding behavior. Additionally, it is important to understand how the feeding behaviors and dietary patterns of other family members may influence people with ASD. This comprehensive approach enables an evaluation of both individual patterns and the broader context of feeding behaviors to which the individual is exposed [180]. Feeding difficulties can manifest as early as the first few months in children with ASD, encompassing challenges with infant feeding practices, introduction of solid foods, and disruptive behaviors during mealtimes [39]. Feeding behaviors can play a protective role against chronic diseases and eating disorders, shaped by various factors. Therefore, understanding how the autistic individual relates to food is crucial to developing effective management strategies [32]. Several tools are available to assess feeding behavior; but no instrument covers all aspects of feeding problems [181], and few scales or questionnaires specifically address behavioral feeding challenges in individuals with ASD [37]. Thus, the instrument’s feeding behavior domain was developed to encompass the various issues described in the literature, ensuring its applicability within the context of autism. This structure facilitates effective use in clinical practice, supporting professionals’ decision-making during consultations and enabling them to assist parents in managing these challenges and their potential outcomes.

Dietary Intake: This domain focuses on evaluating both the quantity and quality of foods consumed. Various methods can be employed to assess dietary intake, including the Food Frequency Questionnaire (FFQ), which, despite its practicality, tends to overestimate energy and nutrient consumption [182]. Another approach is food recall, which relies on recollecting, during the interview, foods consumed [183], and the food diary, completed at mealtime [55]. The latter provides more accurate data and captures essential nutritional details, making it more reliable. Ideally, it should cover at least three non-consecutive days, including one weekend day, with the recording of all foods, beverages, and snacks consumed, serving as a useful tool in clinical practice [55]. However, in the ASD context, engaging caregivers can be challenging, considering the high caregiving demands they already face [160]. The method incorporated into the instrument involves caregivers completing a food diary. Nevertheless, consideration of the challenges and circumstances faced by each family is essential; accordingly, this method should be applied flexibly and adapted to the specific needs of each individual and their caregiver.

Daily routines: This domain enables a deeper understanding of the daily habits and routines of individuals with ASD, offering valuable insights into how these factors may affect their overall health and nutritional status. Understanding communication difficulties is essential, as half of verbally expressive children with ASD exhibit some degree of language impairment [184], while approximately 25% to 30% do not develop functional language or are minimally verbal [140]. The impact of these challenges extends across multiple areas, potentially affecting quality of life, behavior, daily activities, and academic performance [184]. Regarding nutrition, it is crucial to assess the extent of communication challenges and determine whether the individual can express hunger, satiety, or the desire to eat or drink.

Individuals with ASD may face challenges in performing daily tasks. However, it is important to assess whether direct parental intervention might be seen as unnecessary interference, potentially hindering the development of essential skills for greater autonomy, depending on the individual’s abilities [147]. It is crucial to consider how these difficulties can impact nutrition and explore their relationship with school attendance and participation in celebratory events.

Nutritional factors are closely associated to physical activity in maintaining a healthy weight and overall well-being. However, individuals with autism tend to engage less in physical activities [47]. Sedentary behavior in children with ASD may contribute to excess weight and obesity, which are associated with adverse health outcomes, such as insulin resistance, diabetes, and cardiovascular diseases. Additionally, sleep duration and quality have been linked to an increased risk of being overweight [9], as well as to problematic behaviors and core autism symptoms [108].

Children with ASD are exposed to screens earlier and for longer periods compared to peers from other clinical groups, including those with typical development (TD) [107]. Digital technologies, when used appropriately, hold significant educational value. However, for individuals with ASD, excessive and indiscriminate screen use can result in greater negative effects due to heightened sensitivity to stimuli. These include impaired self-regulation, screen dependence, and nutrition-related issues, often driven by unhealthy food choices influenced by advertising linked to the content viewed, as well as increased sedentary behavior, increasing the risk of excessive weight gain [185]. Additionally, parents may face challenges in managing their children’s screen time, even when they are aware of negative consequences [186]. Therefore, assessing screen time and its impact is essential in the context of nutrition.

Clinical Aspects: This domain encompasses a range of individual characteristics that may influence feeding and nutrition. Considering the unique clinical profiles of individuals with ASD, a detailed examination of these aspects is essential for understanding how they may affect nutritional status and feeding behavior. These influences include associated comorbidities, therapeutic interventions, biochemical markers, and medication use. It is estimated that two-thirds of individuals with autism require medication to manage symptoms such as irritability, aggression, mood issues, and anxiety [21], with up to 42% using psychotropic drugs in combination [79]. This can significantly increase the risk of metabolic abnormalities, such as hypertension, dyslipidemia, type 2 diabetes mellitus, and weight gain [23], which makes rigorous biochemical monitoring crucial [21]. These treatments may contribute to disturbances in hunger and satiety signals and their relationship with food, potentially altering feeding behavior, as evidenced by a greater preference for sweets and salty foods with high energy density [187]. Although hormones like ghrelin, which regulates hunger signals, and leptin, which signals satiety, are not typically monitored in clinical nutrition practice, it is important to highlight that, along with other metabolic and hormonal processes, these hormones may be dysregulated in individuals with ASD, contributing to feeding concerns and difficulty in maintaining adequate weight [188].

In the preliminary version, the assessment of biochemical markers was not included. However, based on expert feedback, a subdomain was incorporated into the clinical aspects domain to encompass laboratory tests relevant to nutritional evaluation. Monitoring these markers is essential, given the risk of nutritional imbalances resulting from feeding difficulties and common deficiencies observed in individuals with ASD, such as iron and calcium [87] and vitamins A and D [189]. Deficiencies in folic acid, vitamin B6, and vitamin B12, essential for homocysteine metabolism, have also been observed [93]. Meta-analyses indicate that peripheral blood homocysteine levels are significantly elevated in children with ASD compared to children with TD [86], increasing the risks of cerebrovascular and cardiovascular conditions [190]. Furthermore, an elevated cardiovascular risk has already been reported in individuals with ASD [83].

Gastrointestinal dysfunction is among the most common comorbidities in autism, with a prevalence approximately 2.6 times higher than in the general population, with up to 49% of children with ASD exhibiting one or more chronic gastrointestinal symptoms [191]. Such dysfunctions can significantly impact both behavior and autism manifestations and are associated with increased ASD severity [99]. However, communication difficulties often hinder the identification and characterization of these symptoms, potentially leading to them being overlooked or mistaken for core traits of the condition [192]. Gastrointestinal issues may also correlate with feeding challenges [101]; thus, a comprehensive examination of gastrointestinal aspects, from chewing to elimination and covering the full range of intestinal symptoms and influencing factors, is essential for an accurate nutritional assessment.

Anthropometry: Maintained as a core domain for physical assessment, this section plays a vital role in providing key indicators of health status and developmental progress. The collection of anthropometric data—particularly height and weight, which allow for Body Mass Index (BMI) calculation and growth monitoring—is fundamental to a comprehensive nutritional assessment. However, in the context of autism, obtaining these measurements can present unique challenges. Accordingly, the discussion was expanded to emphasize the importance of a flexible and individualized approach, tailored to each person’s comfort and specific needs. Health professionals are encouraged to avoid unnecessary procedures and to ensure that assessments are conducted in a manner that minimizes discomfort while preserving accuracy and clinical relevance.

The formulation of instruments in healthcare using the Delphi method is widely recognized for its effectiveness, particularly when research is limited or logistical challenges arise. The method is designed to identify priorities, establish guidelines, and develop clinical tools, ideally with input from eight to 23 experts, and can be applied with various modifications [163]. In this study, 30 dietitians specializing in the clinical care of individuals with ASD participated in the content validation, which enabled the refinement of the nutritional assessment instrument, employing a modified Delphi method. Qualitative analysis was used to interpret the recommendations, consistent with other studies in the literature, such as the development of guidelines for diagnosing and supporting autism in women [193], achieving consensus among clinicians on optimal post-diagnostic services for autistic adults [194], and creating sports nutrition questionnaires for athletes [195,196].

Feedback from specialists regarding the first version of the instrument significantly contributed to optimizing the tool. The evaluated domains included quality, functionality, organization, language and comprehension, and comprehensiveness. The selected specialists had different profiles, particularly regarding their experience with individuals with ASD, which may have influenced their responses. All the feedback received was discussed among the authors, and necessary decisions were made to improve the instrument.

To the best of our knowledge, this study presents the first instrument specifically designed for the nutritional assessment of individuals with ASD, integrating science, evidence, and clinical practice. It assesses multiple domains, providing a comprehensive evaluation, and is applicable in clinical practice for initial evaluations, monitoring progress, and addressing specific needs. Further, it can be partially integrated into discussions within multidisciplinary teams. To overcome potential challenges in training clinicians to use the tool, the authors developed a detailed manual alongside the instrument, providing step-by-step guidance on its application. This instrument addresses a critical gap in healthcare by enabling the identification of feeding and nutritional challenges specific to ASD, facilitating targeted interventions, and ultimately improving health outcomes and quality of life for individuals and their families.

The complexity and diversity of needs among individuals with ASD highlight the critical importance of having well-trained and specialized professionals who can deliver effective, individualized interventions that enhance the quality of life for both individuals on the spectrum and their families. Despite this growing need, there remains a significant shortage of clinicians with specialized training in autism-specific care, including the unique nutritional challenges faced by this population.

The evidence-based nutritional assessment instrument developed in this study addresses this gap by providing a comprehensive tool for evaluating key domains that influence the nutrition and feeding behaviors of individuals with ASD. Its structured approach enables even professionals with limited experience in autism to conduct thorough assessments, thereby supporting more informed and effective clinical interventions. By encompassing critical areas such as life history, sensory processing, feeding behavior, dietary intake, and clinical indicators, the instrument facilitates a deeper understanding of the multifactorial elements that affect nutrition in this population.

Moreover, because it can be applied in both initial evaluations and ongoing monitoring, the instrument allows clinicians to track progress longitudinally and adapt care plans to the changing needs of each individual. While cultural and contextual factors will need to be considered during the instrument’s planned validation phase, its current design offers a strong foundation to enhance clinical practice. This tool not only empowers healthcare providers to deliver more personalized and precise nutritional care but also raises awareness of the complex interplay between autism and nutrition, ultimately contributing to improved health outcomes for individuals with ASD.

5. Limitations and Future Directions

Despite being grounded in a broad range of scientific evidence, this instrument has not yet undergone a formal validation process with individuals with ASD. It is important to highlight that all items included are evidence-based, as demonstrated by the supporting material used in its development, which provides initial content validation through expert recommendations. However, further studies are needed to assess the instrument’s validity and reliability in clinical settings.