Associations between rs9939609 polymorphism, serum vitamin D, mental health, and eating behaviors in overweight adults.

Despite the significant role of the Fat Mass and Obesity-Associated (FTO) gene in obesity, the underlying mechanisms are not fully elucidated. Besides, vitamin D deficiency and obesity are mostly seen together, and it can be hypothesized that this nutrient may have an impact in the role of FTO genotype in adiposity. Thus, this study aimed to investigate the association of FTO rs9939609 gene polymorphism with eating behaviors, eating disorders, and general mental health in overweight adults, considering their vitamin D intake as a mediate confounding factor. This cross-sectional study was carried out on 197 overweight adults in Shiraz, Iran. Genotyping was performed through amplification refractory mutation system polymerase chain reaction (ARMS PCR). Mental health, vitamin D intake, eating behaviors and disorders were assessed by the validated questionnaires. The risk allele of the FTO rs9939609 polymorphism (A) was significantly associated with a higher risk of eating behavior and mental health disorders (all P < 0.05). After considering vitamin D intake, the AA genotype carriers had significantly higher risks for poorer eating behavior (P = 0.002), mental health (P = 0.007), and general mental health (P = 0.039) compared with the TT carriers if they had insufficient vitamin D intake. In conclusion, these results indicated that the A-allele of the FTO rs9939609 polymorphism may be associated with poorer eating behaviors, mental health, and higher risk of eating disorders. It was also identified that the effect of FTO rs9939609 A risk allele on eating behavior and mental health may be limited to people with insufficient vitamin D intake.