Finnish Health in Teens Study (Fin-HIT)
Common genetic risk factors predict risk of overweight in preadolescents.
Common obesity is considered a polygenic trait, meaning that it is affected by multiple genes and likely their interactions with lifestyle factors. Today, hundreds of common genetic variants, also known as single nucleotide polymorphisms (SNPs), have been consistently associated with body mass index (BMI) in adults. Together, they explain 6% of the variation in BMI. Somewhat different SNPs have been associated with central obesity, which is considered a better indicator/predictor of obesity-related diseases than BMI. In children, waist-to-height ratio (WHtR) is used to describe central obesity.
We combined well-defined SNPs for BMI and central obesity into genetic risk scores (GRSs) and evaluated their performance in 1,142 preadolescents in the Fin-HIT cohort. The BMI-GRS based on early findings of Speliotes et al. in a discovery cohort of 12,5000 individuals, had the best performance, as it explained 3.7% of the variation in BMI with only 30 SNPs. On the other hand, the GRSs for central obesity were not related to WHtR in our study.
While the GRS was poor in predicting short-term changes in BMI or WHtR in this age group, the combined BMI-GRS was still associated with a higher risk for being overweight/obese – the higher the BMI-GRS, the higher the risk for being overweight/obese. When compared with other lifestyle factors, the effect of GRS was comparable with low physical activity level.
Our findings demonstrate that genetic contributors to overweight in preadolescents are similar to adults, but this does not apply to central obesity. Further studies are needed to evaluate the long-term consequences of genetic risk score and health outcomes after adolescence.
Viljakainen H, Dahlström E, Figueiredo R, Sandholm N, Rounge TB, Weiderpass E. Genetic risk score predicts risk for overweight and obesity in Finnish preadolescents. Clin Obes 9: e12342, 2019 (doi: 10.1111/cob.12342).