Introduction and objective:
The FTO rs9939609 gene variant has been associated with obesity in humans; however, its role in the regulation of dietary intake remains unclear. The aim of the study is to examine the associations between dietary intake, nutritional status, and familial predisposition to overweight and obesity, as well as to evaluate the contribution of the FTO rs9939609 polymorphism in this context.

Material and methods:
The study included 112 adults (74% women; mean age: 40.1 ± 13.2 years). Body composition was assessed using bioelectrical impedance analysis; weight status was classified according to body mass index (BMI). Dietary intake was evaluated using a three-day food records and a food frequency questionnaire. Genotyping of the FTO rs9939609 polymorphism (AA, AT, and TT) was performed using fast real-time PCR on DNA isolated from buccal swabs. Statistical analyses included analysis of variance, non-parametric tests, and multivariate methods.

Results:
The frequency of the A allele was 0.46. Genotype frequencies (TT = 0.26, AT = 0.56, AA = 0.18) were consistent with Hardy–Weinberg equilibrium. The FTO rs9939609 polymorphism was associated with a higher prevalence of excessive body weight. However, no significant differences were observed in anthropometric measurements or body composition parameters between genotype groups. The polymorphism explained 7.82% of the variability in indicators of nutritional status.

Conclusions:
The study supports an association between the rs9939609 polymorphism of the FTO gene and increased susceptibility to excessive body mass, particularly among carriers of the A allele, and a significant influence of relatives along the maternal line. These observations highlight the potential contribution of shared genetic susceptibility and familial environment to obesity.