The strong heritability of obesity has been demonstrated in several twin and adoptee studies, in which obese individuals who were reared separately followed the same weight pattern as that of their biological parents and their identical twin. Metabolic rate, spontaneous physical activity, and thermic response to food seem to be heritable to a variable extent.

A study by Freeman et al found that having an overweight or obese father and a healthy-weight mother significantly increased the odds of childhood obesity; however, having an obese mother and a healthy-weight father was not associated with an increased risk of obesity in childhood. This discrepancy suggests a role for epigenetic factors in hereditary risk.