A new study shows the “obesity paradox,” the idea that obese people live longer than those of normal weight, may be explained by muscle mass.

After accounting for muscle mass, high BMI no longer associates with greater survival. Some have hypothesized that excess fat stores are beneficial for counteracting episodes of catabolic stress. However, the risk of death increased with low muscle mass and greater body fat.

This study also found that skeletal muscle mass was an independent risk factor for mortality in the general population, and this was more pronounced among younger adults…which is interesting because most studies on muscle mass and mortality focus on a geriatric population.

Skeletal muscle mass could directly influence survival and could protect against loss of functional status due to aging or the onset of chronic disease. However, since this is an observational nature study, a causal relationship cannot be determined. There is always the possibility that there may be other confounding health-related factors that were not accounted for.