Yukari Yokota

Effects of rapid or slow body mass reduction on body composition in adult rats.

Whether the speed of body mass (BM) reduction influences the body composition is uncertain. To investigate the effects of rapid vs slow body mass reduction on body composition, rats were divided into three groups; fed ad libitum for 16-day (Control, C); received restricted food intake during 16-day to decrease BM slowly (Slow, S); or fed ad libitum for 13-days and fasted for the last 3 days to rapidly reach a BM comparable to that of S (Rapid, R). Drinking water was restricted for R on day 16 to rapidly decrease their BM. All rats trained during the study. Final BM and adipose tissues mass were similar for R and S, and both were lesser than C. The skeletal muscle mass did not decrease in R and S. The liver mass was lower in R and S than C, and the decrease tended to be greater in R than S. Both the stomach and small intestine masses were significantly lower in R than C, but did not differ between S and C. In conclusion, differences of the speed of BM reduction affect the splanchnic tissues, and the decrease in splanchnic tissue mass was greater with rapid than slow BM reduction.

Effects of short-term refeeding after rapid or slow body mass reduction on body composition in adult rats

SUMMARY We previously observed that digestive tract mass decreased more in rats experiencing rapid body mass (BM) reduction than in those undergoing slow BM reduction. To determine if BM reduction speed influences body composition after refeeding, rats were assigned to three groups. The control group (C) ate ad libitum, the slow group (S) received restricted food for 21 days to slowly reduce BM, and the rapid group (R) ate ad libitum for 18 days and fasted for the last 3 days to rapidly reach a BM comparable to that of S. Water was restricted for R on day 21. After the BM reduction, both R and S were re-fed ad libitum for 12 h and then were sacrificed with C 4-h later. The BM and masses of the carcass, adipose tissue, and small intestine in both R and S did not return to that of C during the 16-h recovery, although no differences were observed between R and S. The liver and stomach mass in both R and S recovered to that of C. The mass and water, protein, total lipid and glycogen content in the skeletal muscle did not differ between R and S. We concluded that body composition after short-term refeeding is not influenced by the speed of BM reduction.:

Differential effects of rapid and slow body mass reduction on body composition during an equivalent weight loss in rats

SUMMARY It is unclear whether the rate of body mass (BM) reduction affects the body composition with an equivalent BM reduction and whether this is influenced by the intensity of BM reduction. To elucidate this, two experiments (Exp.) were conducted. In Exp. 1, the rats fasted for 3 days to decrease BM rapidly (R3); energy was restricted at 85% of their estimated basal metabolic rate to decrease BM slowly, until it reached the same BM as R3 (S20). In Exp. 2, the rats fasted for 7 days (R7); received a restricted diet as in Exp. 1 (S50). The BM decreased 11% in R3 and S20 showed a BM equivalent to R3 on Day 20. In Exp. 2, the BM decreased 18% in R7 and S50 reached the BM of R7 on Day 50. The mass and water and protein in the skeletal muscle and adipose tissue mass did not differ between the groups in both experiments. In contrast, the stomach mass was 12.9% lower in R3 than S20 (P < 0.05) and the liver mass was 9.9% lower in R3 (P = 0.078). In Exp. 2, the stomach and liver masses were 13.2% and 18.2% lower in R7 than S50 (P < 0.05), respectively. The differences in the rate of BM reduction were seen in splanchnic tissues than in skeletal muscles and adipose tissues regardless of BM intensity. The larger BM reduction appeared to be related to a greater difference in the liver mass between the rapid and slow BM reduction.: