Linking diet and planetary health: psychometric evaluation of the climatarian diet adherence scale

Abstract

Background

While the effects of different types of diets on health and their role in weight loss have been researched for many years, their impact on planetary health has been a subject of study for a much shorter time. The amount of clean water polluted, the amount of greenhouse gases generated, and the land required for the production of the food we consume are now also becoming increasingly important. This study aimed to develop a scale to assess adherence to the climatarian diet, a dietary pattern designed to minimize environmental impacts.

Methods

A 25-item draft that was developed by researchers was applied and submitted through a face-to-face survey for data collection. The healthy young adult volunteers participated from a Vocational School in Türkiye. data from 320 associate degree students meeting the inclusion criteria were analyzed from a population of approximately 1,000 students. Scale items measured students’ adherence to climatarian diet. The items were evaluated with content validity following the Lawshe method. The Confirmatory factor analyses were conducted to test construct validity. Initially, exploratory factor analysis (EFA) was used to assess the structure of the scale. Confirmatory factor analysis (CFA) was subsequently used to validate the acquired component structure. Concurrent validity was evaluated using the Prevention with Mediterranean diet (PREDIMED) based assessment. The Cronbach’s alpha coefficient was calculated for reliability. The data were analyzed using IBM SPSS Statistics for Windows version 23.0 and AMOS 23.0.

Results

The sample comprised 73.4% females with a mean age of 20.2 ± 3.2 years. After the factor analysis, the scale was divided into six sub-dimensions (food production, eco-friendly, plant-based nutrition, domestic food production, food waste, and environmental awareness/sustainability). The six-factor solution accounted for 59.26% of the total variance. The developed climatarian diet adherence scale (CDAS) showed good compliance statistics, as established with the confirmatory factor analysis fit indices (χ²/df = 2.226, CFI = 0.950, TLI = 0.939, NFI = 0.914, RMSEA = 0.059), and high reliability (Cronbach’s α = 0.884).

Conclusion

The study provides initial evidence supporting the psychometric properties of the CDAS among young adults in the study population. For planetary health and our future, awareness of climatarian nutrition needs to be increased.

Graphical Abstract

Highlights

A novel Climatarian Diet Adherence Scale (CDAS) was developed to assess environmentally focused dietary behavior.

The CDAS demonstrated a robust six-factor structure, including food production, eco-friendly behavior, and sustainability awareness.

Strong construct validity and high reliability were confirmed (CFA fit indices: CFI = 0.950; RMSEA = 0.059; Cronbach’s α = 0.884).

The scale provides a practical tool to measure climatarian dietary adherence and supports research on planetary health nutrition.

Higher adherence to the Mediterranean diet was associated with climatarian diet adherence.

Introduction

Climate change, often referred to as global warming, constitutes a profound and escalating threat to both the Earth’s biophysical systems and the future of human societies [1]. Today, the interplay between nutrition and climate change is widely recognized as central, reflecting the deep, reciprocal impacts of food production and consumption on environmental systems and of environmental change on nutritional outcomes. Food systems are widely recognized as key contributors to environmental degradation, notably through deforestation, greenhouse gas emissions, and the overexploitation of water resources in agricultural production [2]. These dynamics contribute substantially to biodiversity loss and the aggravation of global warming, with food production, processing, and transportation functioning as central drivers of the associated environmental pressures [2, 3]. Accumulating research and evidence, including key reports published by the Intergovernmental Panel on Climate Change, has highlighted the importance of adopting integrated policies that mitigate climate change while enhancing nutritional outcomes [4, 5]. It is increasingly recognized that the consequences of dietary choices extend beyond individual health to encompass broader, planet-wide environmental impacts [6]. The climatarian diet is a relatively recent dietary paradigm that prioritizes foods selected to minimize an individual’s environmental impact. Formulated as a flexible eating pattern, it does not strictly exclude any foods; instead, it encourages individuals to make informed choices and to opt for lower-impact options whenever possible [6, 7]. Food causes 30% of all global greenhouse gas emissions [8]. Meat causes far higher emissions than plant-based food. But not all meats have the same impact. Each food leads to different carbon emission values; beef emits 25 kg of CO² eq greenhouse gas, egg 2.12 kg of CO² eq greenhouse gas, whole milk 1.06 kg of CO² eq greenhouse gas, while green peas emit 0.36 kg of CO² eq greenhouse gas. Animal products, in general, have a larger carbon footprint than plant-based foods [9]. Although climatarian dietary practices are situated within the broader concept of sustainable diets, climatarian diet adherence represents a more specific, climate-oriented behavioral construct. Sustainable diets are multidimensional and generally encompass several interrelated dimensions, including nutritional adequacy, health, environmental impacts, affordability, and sociocultural acceptability. Accordingly, existing sustainable diet indices have typically been developed as composite measures that integrate multiple indicators across these dimensions, such as dietary quality, greenhouse gas emissions, water consumption, land requirement, resource use, economic affordability, and sociocultural characteristics [10–12]. In contrast, adherence to the climatarian diet specifically concerns the extent to which individuals intentionally adopt dietary practices to reduce the climate-related environmental consequences of food consumption. Therefore, it should not be regarded as a substitute for the broader sustainable diet construct, but rather as a focused behavioral dimension within it. In the present study, this construct is operationalized across six distinct but interconnected domains: food production, eco-friendly practices, plant-based nutrition, domestic food production, food waste, and environmental awareness/sustainability. These domains reflect different behavioral and attitudinal pathways through which individuals may engage with climate-oriented dietary practices. Thus, the proposed construct is not intended to replace the broader concept of sustainable diets or duplicate existing sustainability indices. Rather, it provides a focused assessment of adherence to climate-oriented dietary practices that may complement multidimensional sustainable diet measures by capturing specific domains of individual engagement with environmentally conscious food choices. This distinction also explains the need for a dedicated measurement approach: existing sustainable diet indices primarily characterize the overall sustainability of dietary patterns, whereas a climatarian adherence measure is intended to capture individuals’ engagement in climate-oriented food choices and behaviors. Consequently, the proposed instrument is designed to complement existing sustainable diet indices by providing a more specific assessment of adherence to climate-focused dietary practices rather than duplicating multidimensional measures of overall dietary sustainability.

While the Mediterranean Diet focuses on health by emphasizing whole plant foods and healthy fats, the Climatarian Diet focuses on planetary health. Both are plant-heavy, but the Climatarian diet specifically prioritizes reducing greenhouse gas emissions [9, 13]. In addition, unlike the Climatarian diet, which is primarily motivated by concerns related to environmental sustainability and climate change mitigation, vegan and vegetarian diets are generally adopted for fundamentally different reasons. These reasons often include ethical considerations regarding animal welfare, religious or spiritual beliefs, and personal health values [14]. The climatarian diet is primarily motivated by environmental concerns and promotes limiting the consumption of beef and lamb to approximately one standard serving per week, in view of the disproportionately high climate impact associated with red meat production [15]. There is no data on the number of followers of the climatarian diet because the new diet has yet to become as popular as the other diets discussed. However, a Food and Health Survey conducted by the International Food Information Council (IFIC) indicates that climate-friendly dietary patterns—encompassing flexitarian, plant-based, vegetarian, vegan, and pescatarian diets—were followed by a combined total of approximately 13–15% of the population in 2021. Data for 2024 indicates that this rate has increased to 20%, and 26% of these individuals follow these diets to protect the environment [16]. The climatarian diet also has substantial potential for broader uptake as people become more aware of the environmental impacts of individual actions, particularly those related to food consumption. The climatarian diet promotes the consumption of local, seasonal, and fresh foods that require minimal transportation, refrigeration, and processing. It also emphasizes an overall reduction in meat consumption, with substantial avoidance of ruminant meats (lamb, goat, and beef) and only moderate intake of pork, poultry, and sustainably sourced fish [6]. Pescatarian, vegetarian, and vegan dietary patterns are likewise considered climate-friendly, primarily because they largely or entirely exclude the consumption of red meat [7]. In addition, it is recommended to reduce food waste, reduce the consumption of processed and packaged products, and increase nutritional diversity in the climatarian diet. Decreasing the consumption of animal products and increasing the intake of plant-based foods is essential for achieving a sustainable food system. In doing so, the nutritional needs of the population can be met without exceeding planetary boundaries [8]. According to scientific literature, dietary changes alone could reduce environmental impact by up to 80% [17]. Therefore, increasing awareness of low–environmental-impact eating and determining levels of adherence to the climatarian diet, so as to inform and guide future research, has become increasingly important. Various scales for assessing sustainable eating behavior exist in the literature [18, 19]. One of the most debated aspects of sustainable diets is their low environmental impact [20], and the concept of the climatarian diet focuses on this area as a sustainable dietary model. To date, no validated psychometric instrument exists to specifically measure adherence to the climatarian diet as sustainable nutrition. This study aimed to develop a scale to assess adherence to the climatarian diet, a dietary pattern designed to minimize environmental impacts.

Methods

Location, time, and participants

University students were selected as the target population of the study, as plant-based diets and environmentally friendly initiatives tend to appeal more to younger individuals. The participants of the study were students enrolled at the Vocational School of Health Services of Kırıkkale University, Türkiye. The study was conducted between May and June 2024. Participants were recruited through institutional announcements and the distribution of informational flyers. These efforts were implemented to reach as many eligible students as possible within the target population. In the process of developing a new scale, it is recommended in the literature that the sample size should be at least five times the number of items in the scale [21]. Considering that the draft scale consisted of 25 items, a minimum of 125 participants was deemed necessary. The study population consisted of approximately 1,000 associate degree students, and data from 320 individuals who met the inclusion criteria were analyzed. The inclusion criteria were being between 18 and 64 years of age, not following a vegan, vegetarian, or flexitarian diet, not being pregnant or breastfeeding, and volunteering to participate in the study. The study included students from six different programs (First Aid and Emergency, Anesthesia, Medical Documentation and Secretarial, Medical Laboratory Techniques, Medical Imaging Techniques, Dental Prosthetics Technology, Oral and Dental Health, Home Patient Care) across three departments (Medical Services and Techniques, Dental Services, Healthcare Services) at Kırıkkale University to prevent over- or under-representation of the population. All volunteers who agreed to participate in the study completed the questionnaire in full, despite being informed that they could withdraw at any time without giving a reason. The exclusion criteria for this study were as follows being vegan, vegetarian, or flexitarian, pregnant or lactating, a student in the Department of Nutrition and Dietetics, a registered dietitian, or enrolled in or having graduated from a nutrition-related academic program. The study was announced to the students with the permission of the responsible lecturer, through a brief introduction given before classes. Those who expressed interest in participating completed the questionnaire prepared by the researchers via face-to-face interviews in a suitable setting.

Data collection

The first section of the questionnaire included an item pool developed by the three nutritionists based on a literature review to assess adherence to the climatarian diet. The item pool is the pool of items created by researchers prior to expert consultation, based on a literature review to develop items suitable for the scale’s purpose. The literature review was conducted by searching databases such as PubMed, Science Direct, Proquest, EBSCO and Google Scholar for keywords like climate-friendly nutrition, climatarian, eco-friendly, and reviewing articles that were relevant to the scale’s purpose. This draft scale was designed in a five-point Likert format, with response options ranging from Always, Often, Sometimes, Rarely, and Never. The second section consisted of the PREDIMED (2012), a validated scale for evaluating adherence to the Mediterranean diet. The final section collected data on participants’ demographic and personal characteristics, including age, gender, marital status, employment status, and self-reported body weight and height. Body mass index (BMI) (kg/m²) values were calculated from body weight and height measurements and were classified as < 18.5 kg/m² (underweight), 18.5–24.9 kg/m² (normal weight), 25.0–29.9 kg/m² (overweight), and ≥ 30 kg/m² (obese) [22]. This survey form took approximately 10–15 min to complete. Although a separate pilot testing phase was not conducted in the present study, the comprehensibility and clarity of the items were carefully evaluated during the expert review process. In addition to assessing the content relevance and representativeness of each item, the experts were specifically asked to evaluate whether the wording was clear, understandable, unambiguous, and appropriate for the target population. The feedback obtained during this process was evaluated by the research team, and necessary revisions were made to improve the wording and comprehensibility of the items before the main psychometric evaluation. Following this process, the final version of the scale was established.

Prevention with Mediterranean diet (PREDIMED)

The PREDIMED scale consists of 14 items. Responses are scored by assigning + 1 point for each “yes” answer and 0 points for each “no” answer. Based on the total score, a PREDIMED score of 5 or below indicates “low compliance,” a score between 6 and 9 indicates “moderate compliance,” and a score of 10 or above indicates “high compliance” with the Mediterranean diet [23]. Concurrent validity was evaluated using the PREDIMED based assessment. Although the PREDIMED scale is climate-friendly, its intended use is different; therefore, it was used as a tool to support the validity of the scale when developing a scale for climatarian dietary tendencies.

Statistical analysis

In this study, descriptive data were presented as the mean and standard deviation (SD), and nominal data were presented as the number (n) and frequency (%). The normality of the data distribution was assessed using the Kolmogorov–Smirnov test. For comparisons of more than two groups, a one-way analysis of variance (ANOVA) was conducted, followed by Tukey’s post hoc test. The correlation between the two variables was evaluated using “Pearson Correlation Analysis”. The correlation coefficient evaluation was as follows: 0.00-0.10 (negligible), 0.10–0.39 (weak), 0.40–0.69 (moderate), 0.70–0.89 (strong), 0.90-1.00 (excellent) [24]. The data were analyzed using IBM SPSS Statistics for Windows version 23.0 and AMOS 23.0 [25, 26]. The statistical significance was established at a p-value < 0.05, and all p-values reported were two-tailed.

Content analysis

The Content Validity Index (CVI) and Content Validity Ratio (CVR) were calculated using the Lawshe method [26], which involved 10 experts with over five years of experience in Nutrition and Dietetics evaluating three options: “appropriate”, “appropriate but should be reviewed”, and “not appropriate”.

Item analysis

Correlations between the scores of each item and the total scale score were calculated. Items with item–total correlation values lower than 0.25 were considered for removal.

Construct validity

The theoretical structure of the scale comprised six factors, including Factor 1 (I1, I2, I3, I4, I5, I8 - food production), Factor 2 (I19, I20, I21, I22 - eco-friendly), Factor 3 (I11, I23, I24, I25 - plant-based nutrition), Factor 4 (I6, I7, I10 - domestic food production), Factor 5 (I12, I13, I14, I15 - food waste), and Factor 6 (I9, I16, I17, I18 - environmental awareness/sustainability). To test this theoretical structure and construct validity, an explanatory factor analysis (EFA) with promax rotation was performed.

Reliability

To assess the reliability of the scale, internal consistency analysis was conducted. Cronbach’s alpha coefficient was examined, with values between 0.80 and 1.00 considered to indicate high reliability. Additionally, the Spearman–Brown coefficient was also evaluated.

Ethical approval

The study was carried out in accordance with the ethical standards of the Declaration of Helsinki and received approval from the Non-Interventional Research Ethics Committee of Kırıkkale University (decision no 2024.04.03, date 17.04.2024).

Results

A total of 320 students, 235 (73.4%) female and 85 (26.6%) male, with a mean age of 20.2 ± 3.2 years, participated in the study. The mean BMI of the participants was 22.9 ± 3.5 kg/m², and 67.5% (n = 216) were of normal weight. The majority were unemployed (n = 296, 92.5%), single (n = 312, 97.5%), healthy (n = 280, 87.5%), and had not heard of the concept of the climatarian diet (n = 303, 94.7%) (Table 1).

Table 1.

Students’ sociodemographic characteristics and BMI classifications (n = 320)

		Mean ± SD	Min-Max
Age (years)		20.2 ± 3.2	18–40
BMI (kg/m2)		22.9 ± 3.5	14.9–35.3

		N	Percentage (%)
Sex	Female	235	73.4
	Male	85	26.6
Education status	1st degree	122	38.1
	2nd degree	198	61.9
Working status	Yes	24	7.5
	No	296	92.5
Marital status	Married	8	2.5
	Single	312	97.5
Presence of diseasea	Yes	40	12.5
	No	280	87.5
Heard of the climatarian diet before	Yes	17	5.3
	No	303	94.7
BMI classification	Underweight	23	7.2
	Normal weight	216	67.5
	Overweight	66	20.6
	Obese	15	4.7

BMI Body mass index, SD Standard deviation, N Number

^aHypertension, type 2 diabetes, kidney diseases, epilepsy, thyroid diseases, psychiatric disorders, allergic diseases

Content validity

Following expert evaluation of the initial item pool consisting of 26 items, one item with a Content Validity Ratio (CVR) below 0.62 was excluded from the draft scale. The remaining 25 items had a Content Validity Index (CVI) of 0.977, which is greater than 0.67 and satisfies the content validity of the scale.

Item results

When the item-total correlations in Table 2 were examined, it was observed that the correlations were positive and between 0.341 and 0.699. There was no item from the scale with the item-total correlation values lower than 0.25. The CDAS is a Likert-type scale and no reverse-coded items are included. Total and subdimension scores are obtained by summing item responses, with higher scores indicating a higher level of adherence to the climatarian diet.

Table 2.

The CDAS item analyses results in university students

Item no	Items	Item total
I1	I consume less red meat (such as veal, lamb, beef, and goat meat) because they harm the environment during their production.	0.491
I2	I consume less white meat (such as chicken, turkey, and fish) because they harm the environment during their production.	0.533
I3	I prefer less imported foods because they harm the environment while being delivered to the consumer.	0.600
I4	Since less water is used during the production of vegetables and fruits, I consume more of these foods.	0.519
I5	Since the production of fruits and vegetables causes less damage to the environment, I consume more of these foods.	0.526
I6	I consume vegetables and fruits in season.	0.422
I7	I prefer markets/markets/vendors that sell vegetables and fruits produced nearby.	0.368
I8	To save energy, I prefer foods that do not need to be kept in the refrigerator or freezer.	0.458
I9	I consume less ultra-processed foods (such as salami, sausages, jellybeans, biscuits, chips) because they harm the environment during their production.	0.437
I10	I prefer restaurants/diners/cafes that use local (produced within the country’s borders) food.	0.371
I11	Since legumes (such as chickpeas, lentils, and beans) cause less harm to the environment during their production, I consume them as a protein source instead of meat.	0.536
I12	To reduce food waste, I use leftovers the next day or use them in a different dish.	0.355
I13	I am careful to store/preserve food under appropriate conditions to reduce food waste.	0.344
I14	To reduce food waste, I reduce the amount I consume at meals.	0.423
I15	I reuse food leftovers to reduce food waste.	0.341
I16	By making a list and/or going shopping on a full stomach, I avoid buying unnecessary food.	0.521
I17	Since food in plastic packaging harms the environment, I prefer them less.	0.550
I18	I am careful that the packaging of the foods I buy is made of environmentally friendly materials that dissolve quickly in nature and cause little harm to the environment.	0.699
I19	I am careful that the food I buy has a recycling symbol on its packaging.	0.697
I20	I am careful that the food I buy has terms like “eco” or “environmentally friendly” on its packaging.	0.679
I21	I check the origin information of the grains I buy and prefer those produced locally (produced within the borders of the country).	0.586
I22	I check the origin information of the legumes I buy and prefer those produced locally (produced within the borders of the country).	0.592
I23	Since the production of animal milk harms the environment, I prefer plant-based drinks (such as almond drinks, hazelnut drinks, soy drinks) instead.	0.434
I24	Since plant-based foods (vegetables, fruits, whole grains, legumes, oilseeds) cause less damage to the environment, I increase my consumption of them.	0.642
I25	Since whole grain products do less harm to the environment, I prefer them.	0.643

CDAS The Climatarian Diet Adherence Scale, I item

Exploratory and confirmatory factor analysis

The Kaiser-Meyer-Olkin (KMO) test was conducted to determine whether the sample size was appropriate for factor analysis. KMO values of 0.5–0.6 are classified as acceptable, 0.6–0.7 as appropriate, 0.7–0.8 as moderate, 0.8–0.9 as good, and 0.9-1 as excellent [27]. Accordingly, the results of the KMO test statistics in this study (KMO = 0.844) indicate that the sample size is sufficient. The Bartlett Test of Sphericity was used to investigate whether there was sufficient correlation between the items, a prerequisite for factor analysis. Regarding the test results, a sufficient correlation between the items was determined to be suitable for factor analysis (c²=3096.049; p < 0.001).

Figure 1 shows the path diagram of the six-factor theoretical structure model (F1 Food production, Factor 2 Eco-friendly, Factor 3 Plant-based nutrition, Factor 4 Domestic food production, Factor 5 Food waste, and Factor 6 Environmental awareness/sustainability).

Fig. 1.

Path diagram illustrating the hypothesized six-factor theoretical model underlying climatarian food-related behaviors. The model demonstrates that Environmental Awareness/Sustainability is conceptually associated with Food Production, Eco-friendly Practices, Domestic Food Production, Plant-based Nutrition, and Food Waste, which together represent interrelated dimensions of sustainability-oriented food behaviors. Circles represent latent variables and rectangles represent observed indicators. Single-headed arrows indicate factor loadings, and double-headed arrows represent correlations among latent constructs. Measurement error terms are shown as small circles (e1–e25). Model parameters were estimated using confirmatory factor analysis

When the standardized factor loadings (λ) and t were examined for the model, the factor loadings ranged from 0.470 to 0.882. Table 3 presents the standardized factor loadings, t values, and p values of the items that were calculated for the theoretical model.

Table 3.

Factor loadings, t values, and variances of CDAS in university students

Items	λ	t	p
I8	0.576
I5	0.687	9.559	< 0.001
I4	0.739	10.026	< 0.001
I3	0.737	10.149	< 0.001
I2	0.707	9.782	< 0.001
I1	0.720	9.793	< 0.001
I19	0.882
I20	0.862	33.010	< 0.001
I22	0.815	17.698	< 0.001
I21	0.804	17.109	< 0.001
I11	0.752
I23	0.720	13.361	< 0.001
I24	0.818	15.127	< 0.001
I25	0.84	14.765	< 0.001
I10	0.673
I7	0.470	7.529	< 0.001
I6	0.495	7.897	< 0.001
I9	0.580
I16	0.669	9.756	< 0.001
I17	0.831	11.862	< 0.001
I18	0.876	11.207	< 0.001
I14	0.750
I13	0.722	11.720	< 0.001
I12	0.609	10.343	< 0.001
I15	0.731	12.156	< 0.001

CDAS The Climatarian Diet Adherence Scale, I Item

Figure 2 indicates the scree plot of numbers of factors. The six-factor structure was maintained, despite a notable decrease in the scree plot after the first point, taking into account the theoretical distribution of items, the interpretability of the factors, and the fit indices from the confirmatory factor analysis. The exploratory factor analysis revealed that all six factors had eigenvalues greater than 1.00 [28]. This finding supports the six-factor structure of the scale. The six-factor solution accounted for 59.26% of the total variance (Table 4).

Fig. 2.

Scree plot of the number of factors

Table 4.

Eigenvalues and explained variance of the extracted factors

Factors	Eigenvalue	% Variance	Cumulative %
Factor 1	6.83	27.31	27.31
Factor 2	2.42	9.66	36.97
Factor 3	1.89	7.57	44.55
Factor 4	1.42	5.66	50.21
Factor 5	1.18	4.74	54.94
Factor 6	1.08	4.31	59.26

Factor 1: Food production, Factor 2: Eco-friendly, Factor 3: Plant-based nutrition, Factor 4: Domestic food production, Factor 5: Food waste, Factor 6: Environmental awareness/sustainability

The exploratory factor analysis revealed that all items had factor loadings above 0.40. According to the criteria suggested by Hair et al. (2019) [29], loading values of 0.40 and above indicate a good level of item-factor relationship. This finding demonstrates that the scale’s factor structure is clear and interpretable, supporting its construct validity (Table 5).

Table 5.

Pattern matrix of factor loadings

Items	F1	F2	F3	F4	F5	F6
I1	0.786
I2	0.852
I3	0.707
I4	0.658
I5	0.537
I6				0.703
I7				0.720
I8	0.459
I9						0.620
I10				0.523
I11			0.409
I12					0.745
I13					0.524
I14					0.677
I15					0.715
I16						0.425
I17						0.678
I18						0.459
I19		0.577
I20		0.643
I21		0.906
I22		0.849
I23			0.591
I24			0.803
I25			0.796

I Item

Formal discriminant validity was assessed using the Fornell–Larcker criterion. The Average Variance Extracted (AVE) is a commonly employed validity measure in scale development research, indicating the percentage of variance in a construct explained by its component items [29, 30]. AVE is calculated by averaging the squares of the standardized factor loadings (AVE = Σλ² / n). Here, λ represents the factor loadings, and n represents the number of items. An AVE value of 0.50 or higher indicates that the construct explains at least 50% of the variance and has sufficient convergent validity [30]. According to the analysis results, five of the six factors had AVE values above 0.50, demonstrating sufficient convergent validity. Factor 4’s average variance extracted value was below 0.50. In the initial stages of developing new scales, low AVE values may be observed for some factors due to the heterogeneity of item content. Therefore, it is recommended that this factor be re-evaluated in subsequent validation studies. AVE of factors was 0.513, 0.703, 0.607, 0.314, 0.524, and 0.618, respectively. However, since this study represents a new scale development process, some factors may have low AVE values due to the heterogeneity of item contents and the initial refinement process of conceptual structures. Factor 4 has been retained due to its theoretical contribution, and its re-evaluation in future studies is recommended.

In the confirmatory factor analysis, the fit indices χ2/df, NFI, TLI/NNFI, CFI, and RMSEA were calculated. Some authors recommend N ≥ 200 as a minimum for SEM; Wolf et al. (2013) demonstrated via simulation that models of this complexity often require N = 300–500 for stable estimates [31], and the sample size of this study (n = 320) met this criterion. Upon examining the scale values according to the criteria in Table 6, the χ²/df (2.226), NFI (0.914), TLI (0.939), CFI (0.950), and RMSEA (0.059) values indicated an acceptable-fitting model level [32–34].

Table 6.

Compliance statistics of CDAS in university students

Compliance indices	Criteria	The Climatarian Diet Adherence Scale
χ²/df	≤ 2 or 3	2.226
NFI	0.90–0.95	0.914
TLI (NNFI)	≥ 0.95 can be 0 > TLI > 1	0.939
CFI	≥ 0.95	0.950
RMSEA	< 0.06	0.059

CDAS The Climatarian Diet Adherence Scale, NFI normed fit index, TLI/NNFI Tucker-Lewis Index/non-normed fit index, CFI comparative fit index, RMSEA root mean square error of approximation

The mean PREDIMED score of the students was 8.3 ± 2.5, and 52.8% (n = 169) were in the moderate compliance group. The possible score range from CDAS was 25–125, and the mean value of the participants was 69.5 ± 15.9. The mean CDAS score of those with high adherence to the Mediterranean diet (71.5 ± 16.2) was higher than that of those with low adherence (64.0 ± 14.7) (F = 3.681, p = 0.026). No statistically significant difference was found between the mean CDAS scores of the BMI groups (F = 0.493, p = 0.687). The correlation coefficient between PREDIMED and CDAS scores was r = 0.179, p = 0.001, and this indicates a weak but significant relationship (Table 7). The relationship between CDAS factors and adherence to the Mediterranean diet score was also examined (F1 r = 0.164 p = 0.003; F2 r = 0.183 p = 0.001; F3 r = 0.218 p < 0.001; F4 r=-0.005 p = 0.931; F5 r = 0.013 p = 0.820; F6 r = 0.111 p = 0.047).

Table 7.

Students' CDAS scores according to PREDIMED and BMI classifications

		Mean±SD		Min-Max
PREDIMED		8.3±2.5		0-14
CDAS total		69.5±15.9		25-109
Factor 1		13.8±5.1		6-30
Factor 2		10.8±4.3		4-20
Factor 3		9.1±3.6		4-20
Factor 4		11.3±2.6		3-15
Factor 5		13.1±3.5		4-20
Factor 6		11.4±3.5		4-20

		CDAS
		Mean±SD	Min-Max	F p
PREDIMED	Low adherence (n=46, 14.4%)	64.0±14.7a	29-93	3.681 0.026*
	Moderate compliance(n=169, 52.8%)	69.7±15.7ab	25-108
	High compliance(n=105, 32.8%)	71.5±16.2b	25-109
CDAS*PREDIMED correlation		r=0.179 p=0.001
BMI	Underweight	65.8±16.6	36-97	0.493 0.687
	Normal weight	70.0±15.9	25-108
	Overweight	69.3±13.9	35-102
	Obese	68.8±22.0	25-109

CDAS The Climatarian Diet Adherence Scale, BMI Body mass index, SD Standard deviation

Factor 1: Food production, Factor 2: Eco-friendly, Factor 3: Plant-based nutrition, Factor 4: Domestic food production, Factor 5: Food waste, Factor 6: Environmental awareness/sustainability

ANOVA test was used. ^*p<0.05

Values with different superscript letters (a, b) differ significantly between groups (p < 0.05)

Reliability

The reliability of the scores obtained from the CDAS, developed within the study, was assessed using Cronbach’s alpha coefficient to evaluate how well it distinguishes participants’ eco-friendly behaviors. Cronbach’s alpha, Spearman-Brown (unequal length), and Guttman Split-Half Coefficients were 0.884, 0.781, and 0.778, respectively.

Discussion

As awareness of the adverse impacts of human activities on the planet continues to grow, reducing carbon footprints and adopting more sustainable lifestyles has become increasingly important. The climatarian diet provides guidelines on how to eat foods in a more environmentally conscious manner. The priority of the diet is to reduce the effects of climate change and improve the health of our planet [6]. In this current study, most participants expressed that they had not heard of the climatarian diet concept. Because the concept of the climatarian diet is relatively new, the body of research on this topic in the current literature remains limited. The extent to which the concept of the climatarian diet is known is likely to vary across different populations and should be further explored in future research. However, the finding that the majority of participants in the present study had not previously heard of the climatarian diet underscores the importance of fostering awareness and understanding of this dietary approach. The EAT-Lancet Commission also proposed a global healthy reference diet in 2019, which countries could adapt to suit their individual nutritional and cultural requirements, prioritizing environmental sustainability. The planetary health diet is a predominantly plant based diet rich in fruits, vegetables, whole grains, legumes, nuts and unsaturated oils, with a low-to-moderate amount of seafood and poultry, and a small quantity of red meat, milk and dairy products [35]. The climatarian diet’s concept has only recently appeared in writings, yet studies on environmentally low-impact, plant-based diets related to health and sustainability have been comprehensive, and the idea of flexitarian eating has gained prominence in recent years [6, 19, 36]. According to a study in recent years, the dietary patterns identified as having the lowest environmental impacts were the vegan, climatarian, and Mediterranean diets [6].

Climatarian diet is driven by environmental concern [15]. The scale of adherence to the climatarian diet consists of 6 sub-dimensions that take into account environmental effects. These sub-dimensions include food production, consumption, plant-based nutrition, food selection, food waste, environmental awareness and sustainability. In addition, these sub-dimensions will also help understand which dimension is more effective when determining the levels of adherence to climatarian diet. The findings of the present study provide evidence for the psychometric adequacy of the developed scale and are largely consistent with established criteria and prior scale development research [37–39]. Item–total correlation coefficients ranged from 0.341 to 0.699, and no item exhibited a value below the commonly accepted threshold of 0.25. Item–total correlations exceeding 0.30 are generally interpreted as indicative of satisfactory item discrimination and internal consistency [40]. In this respect, the observed coefficients suggest that all items contribute meaningfully to the construct measured by the scale and support the internal homogeneity of the instrument [41]. The exploratory factor analysis yielded a six-factor structure explaining 59.26% of the total variance. In the social and behavioral sciences, explained variance values above 50% are considered acceptable, particularly for multidimensional constructs [29]. Similar proportions of explained variance have been reported in previous scale development studies, suggesting that the factor structure obtained in the present study is consistent with established methodological standards [42, 43]. The proposed six-factor model was further examined through confirmatory factor analysis. The fit indices obtained—χ²/df = 2.226, NFI = 0.914, TLI = 0.939, CFI = 0.950, and RMSEA = 0.059—indicated an acceptable to good model fit according to widely cited cutoff criteria [44]. Specifically, comparative fit indices (CFI and TLI) above 0.90 and an RMSEA value below 0.06 suggest that the hypothesized measurement model adequately represents the observed data. These results are comparable to, and in some cases stronger than, those reported in similar scale development and validation studies [19]. The high Cronbach’s α coefficient of the scale reflects the consistency level of the scale statements. Cronbach’s alpha coefficients were greater than 0.80, indicating that the scale is highly reliable [45]. The main results of the study were good fit statistics and a highly reliable Cronbach’s α (0.884). Since this study was conducted to measure the adherence to climatarian diet, a valid and reliable measurement tool emerged. The findings indicate that the scale exhibits satisfactory reliability and is suitable for use in scientific research. To our knowledge, it is the first scale in the literature designed to assess adherence to a climatarian diet. Accordingly, this study provides a pioneering contribution and offers a foundation for future research. The scale may be useful for identifying individuals who follow, or are inclined to follow, a climatarian dietary pattern within different populations and for estimating its prevalence. Furthermore, it can be adapted and validated for use in other languages.

The Mediterranean diet has long been recognised not only for its well-documented health benefits but also for its comparatively low environmental impact. Recognized for its low environmental impact, this dietary approach emphasizes foods that minimize ecological footprints across life cycles [46]. Its reliance on plant-based foods, including cereals, fruits, vegetables, and legumes, inherently decreases greenhouse gas emissions and reduces the intensive use of natural resources compared to diets high in animal products [47]. Adopting the Mediterranean Diet appears to significantly reduce greenhouse gas emissions, land use, energy consumption and water use by up to 72%, 58%, 52% and 33% respectively [48]. Our findings indicate that individuals with higher adherence to the Mediterranean diet also exhibit higher levels of adherence to climatarian diet. Incorporating a Mediterranean Diet Adherence Scale (PREDIMED) alongside the Climatarian Diet Adherence Scale has the potential to substantially strengthen the reliability and interpretative power of the present study. Assessing adherence to the well-established Mediterranean diet, which has been extensively validated and is known for its health and environmental benefits, provides a valuable point of reference for evaluating the new climatarian diet adherence scale. The joint use of both scales in this way not only increases the methodological robustness of the study, but also provides a stronger empirical basis for situating climatarian nutrition within the broader framework of sustainable dietary patterns.

Future research directions

Conducting validity and reliability studies of the scale in different age groups and societies will also be effective in raising awareness of climatarian nutrition worldwide. Future research to validate the scale should include expert opinions from different fields (environmental sciences, sustainability studies, climate research, or public health). However, the validation process for future research can be strengthened by incorporating additional sustainability-oriented dietary indices, plant-based dietary indices, sustainable healthy diet index, environmental footprint-related dietary assessment tools, or dietary intake-based approaches. The climatarian diet has considerable potential for wider dissemination and uptake through the engagement of key stakeholders, ambassadors, and influencers operating within corporate settings and across social media platforms. Intervention studies represent another important avenue, using the CDAS as both an outcome and process measure to evaluate the effectiveness of educational, behavioral, or policy-based strategies targeting climatarian nutrition. It would also be informative to investigate the associations between climatarian adherence and health-related outcomes, such as cardiometabolic risk factors, quality of life, and psychological determinants (e.g. environmental concern, pro-environmental attitudes). Finally, future research may seek to establish cut-off points or categorisations (e.g. low, moderate, high adherence) and to integrate the CDAS into digital tools or mobile applications, thereby facilitating its use in public health surveillance, personalised feedback, and large-scale planetary health initiatives. Future studies should aim to validate the Climatarian Diet Adherence Scale (CDAS) in more diverse and larger populations, including different age groups, socioeconomic strata, and cultural contexts, in order to enhance the generalisability of the present findings. Cross-cultural adaptations and translations of the scale, accompanied by rigorous psychometric testing (e.g. measurement invariance across countries or cultures), would be particularly valuable for enabling international comparisons of climatarian dietary behavior. Future studies should establish empirically derived adherence categories or evidence-based cut-off points to enhance the interpretability and practical applicability of the scale.

Strengths and limitations

This study has several notable strengths. First, it introduces, to our knowledge, the first psychometric instrument specifically developed to assess adherence to the climatarian diet, thereby filling an important gap in the literature on sustainable dietary patterns. The scale development process followed a rigorous methodological framework, including content validation based on the Lawshe technique and construct validation through confirmatory factor analysis, which yielded good model fit indices. Furthermore, the six-dimensional structure (food production, eco-friendly behaviour, plant-based nutrition, domestic food production, food waste, and environmental awareness/sustainability) reflects a theoretically grounded and multidimensional conceptualization of climatarian nutrition. The high Cronbach’s α coefficient (0.884) indicates strong internal consistency, supporting the reliability of the Climatarian Diet Adherence Scale (CDAS) for use in research settings. Overall, the study provides a methodologically robust and conceptually comprehensive tool that can serve as a basis for future work in the fields of nutrition, public health, and planetary health.

Despite these strengths, several limitations should be acknowledged. The study sample consisted of healthy young adult volunteers from a single vocational school in Türkiye, which may limit the generalizability of the findings to broader populations with different sociodemographic, cultural, or health profiles. The cross-sectional design precludes any conclusions about the stability of climatarian adherence over time or the scale’s sensitivity to change, for example in response to interventions aimed at promoting sustainable eating behaviors. In addition, all data were obtained via self-report, which may be subject to recall bias and social desirability bias, particularly given the increasing social salience of environmental issues. The inclusion of participants from health-related programs that may be associated with higher health literacy could have influenced item interpretation and self-reported responses. The use of a five-point Likert scale may have restricted response variability and influenced the recovery of the factor structure. Also, the sample consisted predominantly of young, single, female, and unemployed students, which substantially limits the generalizability of the findings to broader populations. The assessment of construct validity was limited by the use of PREDIMED as the primary external dietary measure. Although some conceptual overlap exists between adherence to the Mediterranean diet and climate-oriented dietary practices, PREDIMED does not directly assess dietary sustainability or the environmental impact of food consumption. Therefore, the present findings should be interpreted as providing preliminary evidence of convergent validity rather than definitive criterion validity. Future studies should incorporate sustainability-specific dietary indices, such as the SHED Index, environmental footprint measures, and dietary intake-based assessments of the environmental impact of diet to provide more comprehensive validation of the scale. Another methodological limitation is that the exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were conducted using the same sample. Although this approach has been described as acceptable in certain scale-development contexts, the use of a single sample may increase the risk of capitalizing on chance and may result in an overly optimistic estimation of the stability of the factor structure. Although item comprehensibility was extensively evaluated through expert review, the absence of a separate pilot testing or cognitive interviewing phase represents a limitation, as participants’ direct understanding and interpretation of the items could not be assessed independently.

Conclusions

The current study provides preliminary evidence that the Climatarian Diet Adherence Scale (CDAS) demonstrates acceptable validity and reliability for assessing adherence to the climatarian diet. Establishing a standardized measurement instrument may help reduce ambiguity and inconsistency in the emerging literature on the climatarian diet, although further validation studies are warranted. The environmental consequences of human behavior are occupying an increasingly prominent place in public consciousness as climate change continues to progress and intensify. In addition, today’s adherence to a climatarian diet has become even more important due to climate change. The importance of adherence to the climatarian diet comes to the fore due to its impact on sustainability and environmental health.

As a result, the climatarian diet adherence scale developed for young adults comprises six sub-dimensions and provides preliminary evidence of being a valid and reliable measure of individuals’ adherence to a climatarian diet.

Abbreviations

CDAS

Climatarian Diet Adherence Scale

PREDIMED

Prevention with Mediterranean diet

IFIC

International Food Information Council

IPCC

Intergovernmental Panel on Climate Change

CVI

Content Validity Index

CVR

Content Validity Ratio

EFA

Explanatory factor analysis

KMO

Kaiser-Meyer-Olkin

NFI

Normed Fit İndex

TLI/NNFI

Tucker-Lewis Index/non-normed fit index

CFI

Comparative Fit Index

RMSEA

Root Mean Square Error of Approximation

BMI

Body Mass Index

Authors’ contributions

SED: Conceptualization; data curation; formal analysis; methodology; writing–original draft; writing–review and editing AB: Conceptualization; data curation; formal analysis; methodology; writing–review and editing MA: Conceptualization; data curation; methodology; writing–review and editing EÖ: Methodology; formal analysis, validation, visualization writing–review and editing.

Funding

The current study was conducted without.

Data availability

Data available on request from the authors.

Declarations

Ethics approval and consent to participate

The study was carried out in accordance with the ethical standards of the Declaration of Helsinki and received approval from the Non-Interventional Research Ethics Committee of Kırıkkale University (decision no 2024.04.03, date 17.04.2024). The participants were asked to sign a written informed consent form stating that they participated in the study voluntarily.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.