Association between Mediterranean and Nordic diet scores and changes in weight and waist circumference: influence of FTO and TCF7L2 loci

Background: Several studies have shown that adherence to the Mediterranean Diet measured by using the Mediterranean diet score (MDS) is associated with lower obesity risk. The newly proposed Nordic Diet could hold similar beneficial effects. Because of the increasing focus on the interaction between diet and genetic predisposition to adiposity, studies should consider both diet and genetics. Objective: We investigated whether FTO rs9939609 and TCF7L2 rs7903146 modified the association between the MDS and Nordic diet score (NDS) and changes in weight (Delta weigh), waist circumference (Delta WC), and waist circumference adjusted for body mass index (BMI) (Delta WCBMI). Design: We conducted a case-cohort study with a median follow-up of 6.8 y that included 11,048 participants from 5 European countries; 5552 of these subjects were cases defined as individuals with the greatest degree of unexplained weight gain during follow-up. A randomly selected subcohort included 6548 participants, including 5496 noncases. Cases and noncases were compared in analyses by using logistic regression. Continuous traits (ie, Delta weight, Delta WC, and Delta WCBMI) were analyzed by using linear regression models in the random subcohort. Interactions were tested by including interaction terms in models. Results: A higher MDS was significantly inversely associated with case status (OR: 0.98; 95% CI: 0.96, 1.00), Delta WC (beta = -0.010 cm/y; 95% CI: -0.020, -0.001 cm/y), and Delta WCBMI (beta = -0.008; 95% CI:-0.015, -0.001) per 1-point increment but not Delta weight (P = 0.53). The NDS was not significantly associated with any outcome. There was a borderline significant interaction between the MDS and TCF7L2 rs7903146 on weight gain (P = 0.05), which suggested a beneficial effect of the MDS only in subjects who carried 1 or 2 risk alleles. FTO did not modify observed associations. Conclusions: A high MDS is associated with a lower Delta WC and Delta WCBMI, regardless of FTO and TCF7L2 risk alleles. For Delta weight, findings were less clear, but the effect may depend on the TCF7L2 rs7903146 variant. The NDS was not associated with anthropometric changes during follow-up.