Role of Nonexercise Activity Thermogenesis in Resistance to Fat Gain in Humans

TLDR

Humans exhibit marked interindividual differences in weight‑gain susceptibility when overfed. The study measured energy storage and expenditure in 16 nonobese volunteers during an 8‑week period of 1000‑kcal/day overfeeding. Increased NEAT accounted for two‑thirds of the rise in total daily energy expenditure, explained the 10‑fold variation in fat storage, and strongly predicted resistance to fat gain during overfeeding (r = 0.77, p < 0.001), showing that NEAT activation preserves leanness while its failure promotes fat gain.

Abstract

Humans show considerable interindividual variation in susceptibility to weight gain in response to overeating. The physiological basis of this variation 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 activity thermogenesis (NEAT), which is associated with fidgeting, maintenance of posture, and other physical activities of daily life. Changes in NEAT accounted for the 10-fold differences in fat storage that occurred and directly predicted resistance to fat gain with overfeeding (correlation coefficient = 0.77, probability &lt; 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.