Effects of the Speed of Body Weight Loss on Body Composition Changes and Energy Density for Body Weight Loss in Exercised Rats

Abstract

We examined the effects of the speed of body weight (BW) loss on changes in the body composition and energy required for BW loss in exercised rats. Rats (average BW: 275 g), were divided into a rapid weight reduction group (Rapid, n = 5), which was fasted for 3 days, and a slow weight reduction group (Slow, n = 5), which had their food restricted for 17 days in order to achieve comparable BW loss to the Rapid group. The rats were placed individually into a metabolic chamber with a 1‐m ladder inside. The water bottle was set at the top of the chamber, forcing the rats to climb the ladder to drink. The BW loss was −42.7 g (standard deviation [SD] 4.2) in the Rapid group and −43.8 g (SD 4.9) in the Slow group. The total energy expenditure was 95.1 kcal (SD 10.7) in the Rapid group and 555.6 kcal (SD 69.3) in the Slow group. Since the metabolizable energy was 0 kcal in the Rapid group and 521.1 kcal (SD 44.9) in the Slow group, the energy deficit was −95.1 kcal (10.7) in the Rapid group and −34.5 kcal (72.7) in the Slow group. Therefore, the energy density for BW loss by 1 kg was not significantly different between the Rapid group (2246 kcal [SD 320.3]) and the Slow group (734.6 kcal [SD 1631.6]). The estimated changes in the lean tissue (LT) and adipose tissue (AT) based on the energy density of LT (1.25 kcal/g) and AT (7.6 kcal/g) and the energy deficit did not differ significantly between the groups (LT: −36.0 g [SD 5.4] and AT: −6.8 g [SD 1.9] in the Rapid group and LT: −47.1 g [SD 11.8] and AT: 3.3 g [SD 11.6] in the Slow group). Therefore, the speed of BW loss had no marked effect on the changes in the body composition and energy required for BW loss in exercised rats. However, the increase in the AT observed in the Slow group is theoretically unlikely, suggesting the overestimation of energy intake (metabolizable energy) due to a decrease in the absorption rate or an increase in the energy density in the AT in this group.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.