Resistance to weight gain during overfeeding: a NEAT explanation

Individuals vary in susceptibility to weight gain in response to overeating; however, the reason for such variation has never been clear. A recent study of 16 nonobese young adults followed on an ambulatory basis for 8 weeks found that changes in nonexercise activity thermogenesis (NEAT) account for the variations in fat storage that occur in response to experimentally controlled overeating. NEAT is the thermogenesis that accompanies physical activity other than volitional exercise. Individuals in whom overeating effectively activates NEAT dissipate as much as 69% of the excess energy as heat. Those less able to activate NEAT store a higher proportion of the excess calories as fat. Other studies have shown that genotype is an important determinant of resistance to overfeeding-induced weight gain. Spontaneous weight gain is accompanied by rises in plasma norepinephrine, insulin, and leptin levels, suggesting that a change in autonomic nervous system activity or in pattern of hormonal secretion might play a role in the activation of overeating-induced NEAT