Type 2 diabetes (T2D) is a complex metabolic disorder characterized by chronic hyperglycemia resulting from insulin resistance and/or β-cell dysfunction (1). Globally, its prevalence has risen alarmingly, affecting an estimated 537 million adults in 2021, with projections suggesting an increase to 783 million by 2045 (2). Saudi Arabia faces a particularly high burden, with a national prevalence of 18.3%—ranking among the top ten countries worldwide for T2D rates (3). This surge has been linked to rapid urbanization, sedentary lifestyles, Westernized diets, and high obesity rates (4).

Type 2 diabetes is associated with severe complications, including cardiovascular disease, nephropathy, neuropathy, retinopathy, and premature mortality (5). These conditions not only impair quality of life but also impose substantial economic and healthcare burdens, underscoring the need for effective preventive strategies targeting modifiable risk factors (5).

The development of T2D is influenced by both non-modifiable factors (e.g., genetics, age, ethnicity) and modifiable lifestyle factors, such as physical inactivity, obesity, poor diet, and smoking (6). Among these, dietary habits play a pivotal role by affecting body weight, glycemic control, and systemic inflammation—key pathways in T2D pathogenesis (7).

Nutritional interventions promoting healthy eating patterns are crucial for T2D prevention and management. Evidence consistently supports diets rich in fruits, vegetables, whole grains, legumes, nuts, and healthy fats, while discouraging processed foods, refined grains, added sugars, and saturated fats, for improving insulin sensitivity and reducing T2D risk (8–10).

Recently, the Dietary Obesity-Prevention Score (DOS) was developed to quantify adherence to dietary patterns associated with lower obesity risk—a major T2D driver (11). The DOS emphasizes protective foods (e.g., fruits, vegetables, legumes, yogurt, nuts, fish) and limits red meat, processed foods, saturated fats, and sugary beverages. However, despite growing recognition of dietary patterns’ importance, the specific relationship between DOS and T2D risk remains understudied.

Given Saudi Arabia’s high T2D prevalence and the established link between obesity-related diets and T2D, this case-control study aimed to investigate the association between DOS adherence and T2D incidence in a Saudi adult population.

The demographic and anthropometric characteristics of the study participants are detailed in Table 1. The mean age of participants was 43.1 years, with an overall mean BMI of 27.8 kg/m². Participants diagnosed with T2D exhibited significantly higher mean body weight (71.5 vs. 65.3 kg) and BMI (29.4 vs. 26.2 kg/m²) compared to the control group (p < 0.05). Additionally, the T2D group demonstrated greater mean waist circumference (WC) and waist-to-height ratio (WHtR) (106. vs. 92.4 cm), a difference that was statistically significant (p = 0.036). Marital status and educational attainment also differed between groups: individuals with T2D were more likely to be married and less likely to have attained a college-level education (p < 0.05 for both comparisons). No other statistically significant differences were observed between the case and control groups (p > 0.05).

Table 2 presents the mean and standard error of dietary intakes across DOS tertiles. Participants in the highest DOS tertile had significantly greater daily energy intake (2,611 vs. 2,102 kcal/d) and carbohydrate intake (341 vs. 291 g/d) compared to those in the lowest tertile (p < 0.05). Intakes of iron, zinc, magnesium, vitamin E, vitamin C, vitamin B9, vitamin B1, vitamin B6, fruit, vegetables, whole grains, fiber, legumes, and the vegetable-to-animal protein ratio were also significantly higher in the highest DOS tertile (p < 0.05). Conversely, saturated fatty acid, vitamin A, refined grain, ultra-processed food, and sugary beverage intakes were significantly lower in the highest DOS tertile (p < 0.05). No statistically significant differences (p > 0.05) were observed between DOS tertiles for protein, fat, cholesterol, polyunsaturated fatty acids (PUFAs), monounsaturated fatty acids (MUFAs), calcium, selenium, vitamin D, vitamin B12, yogurt, nuts, fish, red meat, processed meat, and animal fat consumption.

Table 3 presents the odds ratios (OR) and 95% confidence intervals (CI) for the association between the Dietary Obesity-Prevention Score (DOS) and the odds of type 2 diabetes (T2D) across different models. In the crude model, higher DOS scores (tertiles 2 and 3) were associated with a statistically significant reduction in T2D odds (OR = 0.63, 95% CI: 0.43, 0.85; P-trend = 0.012). This protective trend remained significant after adjusting for age, sex, and daily energy intake in Model 1 (OR = 0.71, 95% CI: 0.60, 0.91; P-trend = 0.042). Further adjustments for education, marital status, waist circumference, WHtR, and physical activity in Model 2 strengthened the association (OR = 0.53, 95% CI: 0.34, 0.76; P-trend = 0.032). Finally, in Model 3, which included additional adjustment for BMI, higher DOS scores were associated with a statistically significant reduction in T2D odds (OR = 0.58, 95% CI: 0.38, 0.87; P-trend = 0.038).

This case-control study provides novel evidence that higher adherence to the Dietary Obesity-Prevention Score (DOS) is significantly associated with lower odds of type 2 diabetes (T2D) among Saudi adults, even after comprehensive adjustment for potential confounders. Our findings indicate that individuals in the highest DOS tertile were substantially less likely to develop T2D compared to those in the lowest tertile, supporting the hypothesis that a diet rich in plant-based foods and low in processed and sugary products confers metabolic protection.

The DOS, originally developed to predict the risk of overweight and obesity, captures a dietary pattern characterized by high consumption of fruits, vegetables, legumes, nuts, and whole grains, and low intake of processed foods, red and processed meats, saturated fats, and sugar-sweetened beverages (14). This dietary pattern aligns closely with global recommendations for chronic disease prevention, including those from the World Health Organization and the American Heart Association, which emphasize plant-forward, minimally processed diets for reducing the burden of metabolic and cardiovascular diseases (15–17).

Several studies have investigated the association between DOS and the risk of various chronic diseases. One study reported that greater adherence to the DOS was associated with reduced risks of obesity, lower blood pressure, and decreased serum LDL levels in individuals with obesity (18). In another study, Mahabady et al. found a significant inverse association between DOS adherence and inflammation markers. However, no significant relationship was observed between DOS and the odds of developing polycystic ovary syndrome (PCOS) (19). To date, no studies have examined the association between the Dietary Obesity-Prevention Score and the risk of type 2 diabetes.

Mechanistically, the protective effects of a high DOS diet may be attributed to several factors. Diets rich in fiber, antioxidants, and anti-inflammatory compounds-such as those emphasized by the DOS-are known to improve insulin sensitivity, reduce systemic inflammation, and enhance glycemic control (16). In our study, participants in the highest DOS tertile reported greater intake of fruits, vegetables, legumes, and whole grains, consistent with a fiber-rich dietary pattern. Dietary fiber not only slows gastric emptying and reduces postprandial glucose spikes, but also undergoes fermentation by gut microbiota to produce short-chain fatty acids (SCFAs), such as butyrate, which have been shown to improve beta-cell function and increase GLP-1 secretion, further supporting glycemic regulation (20, 21). Dietary fiber plays a significant role in glycemic control and improving insulin sensitivity among individuals with type 2 diabetes. One of the key mechanisms involves slowing gastric emptying and reducing the rate of glucose absorption in the intestine, which leads to lower postprandial glycemic responses (21, 22). These mechanisms are supported by a growing body of evidence linking high-fiber diets to lower T2D risk and improved blood glucose control in both healthy and diabetic populations.

Our findings also reinforce the role of limiting unhealthy dietary components-such as refined grains, processed meats, and sugar-sweetened beverages-in diabetes prevention. Numerous large-scale studies have shown that high intake of processed and red meats, as well as sugary drinks, is consistently associated with increased T2D risk, while diets emphasizing whole foods confer protective effects (23–26). In our sample, higher DOS scores were associated with lower consumption of these risk-enhancing foods, which likely contributed to the observed reduction in T2D odds.

Notably, although the DOS was designed as an obesity-prevention tool (14), our analysis found no significant difference in BMI across DOS tertiles. This suggests that the observed association with T2D risk may be mediated more by overall dietary quality and metabolic effects than by differences in body composition per se.

Our results also resonate with broader research on diet quality indices, such as the DASH, Mediterranean, and AHEI patterns, which have been linked to reduced risk of T2D, cardiovascular disease, and some cancers (27, 28). The DOS, by capturing both positive (protective) and negative (risk-enhancing) food group intakes, offers a practical and evidence-based tool for identifying individuals at higher metabolic risk and guiding dietary counseling in clinical and public health settings.

Although the total fruit and vegetable intake exceeded the 400 g/day recommended by the World Health Organization (WHO) across all tertiles of the DOS, this likely reflects culturally specific dietary habits in the studied population. High fruit consumption, while generally beneficial due to its fiber, vitamins, and antioxidant content, may pose glycemic challenges in individuals at risk of T2D, particularly when consumed in large quantities with high glycemic fruits. Additionally, higher DOS tertiles were associated with increased consumption of whole grains and decreased intake of refined grains and sugary foods, which may contribute to better glycemic control and lower T2D risk. These findings support the potential of DOS as a useful tool to capture adherence to health-promoting dietary behaviors, especially when aligned with broader dietary quality indices. This adjustment strengthens the validity of our findings, ensuring that observed associations are more likely to be due to dietary differences rather than confounding influences.

Our study’s strengths include the use of a validated FFQ tailored for the local population, application of a comprehensive DOS, and adjustment for multiple confounders. Despite these strengths, several limitations should be considered. As a case-control study, causality cannot be established, and recall bias in dietary assessment is possible. Although we adjusted for a wide range of confounders, residual confounding cannot be ruled out. Additionally, the cross-sectional nature of the dietary assessment precludes evaluation of long-term dietary patterns and their temporal relationship with T2D onset. Future longitudinal and interventional studies are warranted to confirm these associations and elucidate underlying mechanisms.

Adherence to a DOS-aligned dietary pattern, emphasizing nutrient-dense foods and minimizing processed and sugary products, is associated with lower odds of T2D among Saudi adults. Further longitudinal studies and randomized controlled trials are required to confirm these findings and elucidate causal pathways.