Adherence to the Mediterranean diet and its association with atherogenic indices and lipid profile in individuals seeking a weight-loss dietary program: what role for body fat?

Background: The Mediterranean diet is widely recognized for its cardiovascular benefits, but its specific effects on atherogenic indices remain unclear, particularly in individuals seeking a weight-loss dietary program, where excess fat mass may mitigate the diet's protective effects. Methods: To explore this relationship, a cross-sectional study was conducted involving 10,286 participants enrolled in a weight-loss dietary program. Anthropometric and biochemical data were collected, and adherence to the Mediterranean diet was assessed using the 14-item Mediterranean Diet Adherence Screener questionnaire. Lipid profiles, including total cholesterol, LDL-C, HDL-C, and triglycerides, were analyzed to calculate the following atherogenic indices: atherogenic index of plasma, Castelli risk indices I and II, lipoprotein combine index, atherogenic coefficient, and atherogenic combined index. Results: Multivariate linear regression models, adjusted for sex, age, body mass index, smoking, physical activity, sociodemographic factors, and use of lipid-lowering medications, showed that each one-point increase in the Mediterranean diet adherence score was significantly associated with reductions in the atherogenic index of plasma (- 0.003, 95%CI: 0.006, - 0.000), the atherogenic coefficient (- 0.013, 95%CI: - 0.024, - 0.001), Castelli risk index I (- 0.013, 95%CI: - 0.024, - 0.001), and the atherogenic combined index (- 0.004, 95%CI: - 0.007, - 0.000), with a marginal association observed for Castelli risk index II (- 0.009, 95%CI: - 0.019, 0.000). Significant associations were also observed for total cholesterol (- 3.453 mg/dl, 95%CI: -5.911, -0.995), LDL (- 3.225 mg/dl, 95%CI: -5.402, -1.048), and HDL-C concentrations (+ 0.255 mg/dl, 95%CI: 0.098, 0.412). However, except for HDL, these associations lost statistical significance after adjusting for body fat percentage. Significant interactions between Mediterranean diet adherence score and body fat percentage were observed for several atherogenic indices, including the atherogenic coefficient, Castelli risk index I, Castelli risk index II, and the atherogenic combined index as well as for total cholesterol and LDL, suggesting that the protective effects of the Mediterranean diet diminish as fat mass increases. Conclusions: Although adherence to the Mediterranean diet is associated with more favorable lipid profiles and atherogenic indices, these benefits are modulated by body composition, particularly fat mass. These findings highlight the importance of integrated dietary strategies that combine nutritional quality with body fat reduction to support cardiovascular prevention.