Why Do Some People Develop Obesity Despite High Levels of Physical Activity?

We know that exercise levels alone don't fully explain a person's tendency to obesity. To explore the potential genetic basis for at least some of this variability, investigators used step count and genetic data from an existing U.S. population-based data set. Genetic risk for obesity was determined by using known loci from a prior genome-wide association study to create quartiles of polygenic risk score (PRS) for 3100 adults (median age, 53) of European ancestry who were not obese at baseline (median body-mass index, ≈24.5 kg/m²).

Participants walked a median 8300 steps daily at baseline and were followed for a median 5.4 years, during which obesity developed in 13% of those in the lowest PRS quartile and 43% in the highest quartile. Both s…