AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 5 1380-R1387, Copyright © 1996 by American Physiological Society
Enhanced thermogenesis during recovery from diet-induced weight gain in the rat
N. G. Almeida, D. A. Levitsky and B. Strupp
Department of Psychology, Cornell University, Ithaca, New York 14853-6301, USA.
The present study examined the contribution of energy expenditure to the
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 received the control
diet for 18 days of recovery. Both overfeeding protocols significantly
increased weight above control levels. This difference disappeared after 7
days of recovery. Increases in resting oxygen consumption, serum
3,5,3'-triiodothyronine (T3) levels, and the thermogenic response to
norepinephrine were observed at the end of overfeeding. Serum T3 and
resting oxygen consumption returned to control levels by day 3 of recovery
from overfeeding, whereas the thermogenic response to norepinephrine
required 9 days to recover. Whereas total energy expenditure was not
significantly elevated during overfeeding, significant increases of 9.6 and
13.9% were observed in the formerly high-fat and tube-fed animals,
respectively, during recovery. These data indicate that changes in energy
expenditure play an important role in maintaining the stability of body
weight.
