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Abstract Background This study aims to verify the relationship between screen and sleep time, body mass index (BMI) and immunological factors with telomere length according to leisure-time physical activity (PA) in children and adolescents. Methods A cross-sectional study involving a sample of 476 schoolchildren of both sexes, aged seven to 17 years, from a community in southern Brazil. Behavioral variables (PA, sleep time, and screen time) were self-reported using a questionnaire. PA was classified as inactive and any PA (doing some physical activity). The associations of screen time, sleep time, BMI, and immunologic factors with telomere length were tested using multiple linear regression models, with the sample divided according to the schoolchildren’s leisure-time physical activity practices. Results An inverse association between BMI and telomere length (β: -0.239; 95% CI: -0.468; -0.010) and a direct association of leukocytes (β: 0.151; 95% CI: 0.029; 0.278) and neutrophils (β: 0.131; 95% CI: 0.008; 0.254) with telomeres were found in the inactive students. No association was found between screen time and sleep time and telomeres. No association was found among students who engaged in any PA. Conclusion The associations between telomeres, BMI, and immunologic factors were found only in inactive students. These results suggest that the association between BMI and immunological factors and telomere length may be influenced by physical activity.

Abstract Background The behavior of anthropometrics and the relationship with genetic factors through a long-term perspective should be better explored. This study aims to verify the odds of maintaining the nutritional status classification after three years, according to the rs9939609 polymorphism (FTO gene). Methods It was a retrospective longitudinal study with 355 schoolchildren (7–17 years). Body mass index, body-fat percentage (BF%), and waist circumference (WC) were measured at baseline and follow-up. The FTO gene was evaluated from blood collection and genotyping performed by real-time polymerase chain reaction. Odds ratios and 95% confidence intervals were calculated. Results For those homozygous with the A allele, the odds of being at less favorable classification at follow-up were 2.29 (1.24; 4.22) and 4.05 (2.08; 7.86) times higher than expected for BF% and WC, respectively, whereas the odds of being in the more favorable classification at follow-up were 0.34 (0.12; 0.93) and 0.11 (0.01; 0.78) for BF% and WC, respectively. The odds of being at less favorable classification were higher for AA carriers with less favorable classification at baseline for BF% and WC compared to AT and TT carriers. Conclusions Schoolchildren with a genetic predisposition to obesity and unfavorable anthropometric profile at baseline had more chances of maintaining their nutritional status after three years of follow-up.