ENHANCED THERMOGENESIS DURING RECOVERY FROM DIET-INDUCED WEIGHT-GAIN IN THE RAT

The present study examined the contribution of energy expenditure to t he recovery of body weight after a period of overfeeding. Three groups of 2-mo-old female rats (n = 24) were fed, respectively, a 10% (wt/wt )-fat diet (control), a 35% (wt/wt)-fat diet (high fat) or were force fed 130% of the control diet (tube fed). After 30 days, all groups rec eived the control diet for 18 days of recovery. Both overfeeding proto cols significantly increased weight above control levels. This differe nce disappeared after 7 days of recovery. Increases in resting oxygen consumption, serum 3,5,3'-triiodothyronine (T-3) levels, and the therm ogenic response to norepinephrine were observed at the end of overfeed ing. Serum T-3 and resting oxygen consumption returned to control leve ls by day 3 of recovery from overfeeding, whereas the thermogenic resp onse to norepinephrine required 9 days to recover. Whereas total energ y expenditure was not significantly elevated during overfeeding, signi ficant increases of 9.6 and 13.9% were observed in the formerly high-f at and tube-fed animals, respectively, during recovery. These data ind icate that changes in energy expenditure play an important role in mai ntaining the stability of body weight.