Role of nonexercise activity thermogenesis in resistance to fat gain in humans

Humans show considerable interindividual variation in susceptibility to wei ght gain in response to overeating. The physiological basis of this variati on was investigated by measuring changes in energy storage and expenditure in 16 nonobese volunteers who were fed 1000 kilocalories per day in excess of weight-maintenance requirements for 8 weeks, Two-thirds of the increases in total daily energy expenditure was due to increased nonexercise activit y thermogenesis (NEAT), which is associated with fidgeting, maintenance of posture, and other physical activities of daily life. Changes in NEAT accou nted for the 10-fold differences in fat storage that occurred and directly predicted resistance to fat gain with overfeeding (correlation coefficient = 0.77, probability < 0.001). These results suggest that as humans overeat, activation of NEAT dissipates excess energy to preserve Leanness and that failure to activate NEAT may result in ready fat gain.