Adaptation to low calorie intake in obese mice: contribution of a metabolic component to diminished energy expenditures during and after weight loss
Dulloo, A.G.; Calokatisa, R.
International Journal of Obesity 15(1): 7-16
1991
ISSN/ISBN: 0307-0565 PMID: 2010261 Document Number: 386464
Adaptive changes in energy expenditure (EE) in response to low energy intake were assessed quantitatively in obese mice using techniques that measure EE chronically over weeks (by the comparative carcass method), and also over 24 h (by indirect calorimetry). Grossly obese mice were given 50% of their normal energy intake until their body weight reached that of the lean. They were subsequently maintained in the post-obese state by continued food restriction at 25% below the obese controls, or refed at the same energy intake as controls. Total EE (assessed over 3-week periods) fell by 30% during weight loss (obese controls 1356 vs. obese-slimmed 966 kJ, P<0.001), by 25% during maintenance of the post-obese weight (obese control 1443 vs. post-obese 1062 kJ, P<0.001), and remained reduced by 17% during weight regain upon refeeding (obese control 1443 vs. slimmed/refed 1176 kJ, P<0.001). Similar reductions in daily oxygen consumption were also obtained by indirect calorimetry, and as a function of lean body mass, 24 h VO2 were lower than controls by 17, 9 and 10%, respectively (P<0.01). It is calculated that in these obese mice, a metabolic component (unassociated with changes in lean body mass and activity) comprised nearly two-thirds of the adaptive fall in EE during weight loss, and one-half of the change in EE during both phases of post-obese weight maintenance and during weight regain. Results support the notion that in response to low energy intake, adaptive changes in the efficiency of cellular energy utilization are of considerable quantitative importance in the resistance to weight loss and in the ease with which the obese condition is rapidly regained after slimming.