AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 4 874-R883, Copyright © 1995 by American Physiological Society
Dissociation between food intake, diet composition, and metabolism in parabiotic partners of obese rats
R. B. Harris, R. J. Martin and R. C. Bruch
Department of Foods and Nutrition, University of Georgia, Athens 30602 USA.
When one member of a parabiosed pair of rats is overfed, its ad libitum-fed
partner loses body fat in the absence of a statistically significant
decrease in food intake. Three experiments investigated the relationships
between food intake, metabolism, and body composition in this model. In
vivo measurement of lipogenesis confirmed that loss of fat is associated
with decreased fat deposition. When partners of overfed rats were compared
with food-restricted single rats, proportional changes in body composition
and metabolism were similar for the two treatments, although there was no
significant change in the food intake of parabiotic rats, whereas
restricted rats received only 60% of the intake of their controls. The
final experiment demonstrated that changes in body composition of partners
of overfed rats were independent of dietary composition. These results
suggest that, when a rat is made obese by overfeeding, a circulatory factor
is released that inhibits fat deposition and disrupts regulatory mechanisms
that normally stimulate food intake during a period of negative energy
balance.
