AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 2 250-R257, Copyright © 1992 by American Physiological Society
Underfeeding and body weight regulation in normal-weight young men
M. B. Heyman, V. R. Young, P. Fuss, R. Tsay, L. Joseph and S. B. Roberts
Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge 02139.
The mechanisms of energy regulation invoked by moderate dietary restriction
were investigated in seven healthy young men of normal body weight leading
unrestricted lives. Following a baseline period of weight maintenance,
subjects were underfed by 806 +/- 162 (mean +/- SE) kcal/day for 21 days.
Changes in total energy expenditure (TEE) and resting energy expenditure
(REE) and subsequent voluntary nutrient intakes were measured. The REE,
averaged for fasting and fed states, decreased during underfeeding by 100
+/- 29 kcal/day (P less than 0.01). TEE decreased nonsignificantly by 296
+/- 170 kcal/day, equivalent to an average of 37% of the decrease in energy
intake. Body energy stores were estimated to decrease by 510 +/- 172
kcal/day (P less than 0.03), thus compensating for 63% of the dietary
energy deficit on average. Voluntary energy intake following dietary
restriction increased above the initial amount required for body weight
maintenance, was proportional to the weight loss during underfeeding (P
less than 0.03), and was associated with a rapid regain of weight lost
during underfeeding. These results indicate that energy balance is
regulated by adaptive variations in both energy intake and energy
expenditure in normal-weight young men leading unrestricted lives but do
not support the hypothesis that energy-wasting mechanisms contribute
substantially to body energy regulation.
