Short-term weight cycling in aging female rats increases rate of weight gain but not body fat content

Abstract

OBJECTIVE: To examine the effects of short-term repeated weight cycling (WC) above and below the baseline (BL) body weight (BW) on body weight regulation, feeding ef®ciency, and fat content in old female Wistar rats when dietary fat content was kept constant. DESIGN: Completely randomized. ANIMALS AND METHODS: Female Wistar rats, 11 months old at the beginning of the study, were randomly divided into six groups (12 per group) after a group of rats (BL) was sacri®ced for baseline data collection: the high fat gain (HFG) group gained weight to 20% above the BL weight with a high fat diet (HF) and returned to BL level by food restriction (50% of ad-libitum amount) for ®ve cycles; the high fat loss (HFL) group lost weight to 20% below the BL weight by food restriction (50% of ad-libitum amount) and regained to BL level by ad-libitum feeding for four cycles; the high fat ad-libitum (HFA) and low fat ad-libitum (LFA) groups were fed HF and low fat (LF) diet, respectively, adlibitum for the entire study; the high fat restricted (HFR group) and low fat restricted rats (LFR group) were fed the HF and LF diet, respectively, in restricted amounts to maintain BW at BL level. RESULTS: A trend of increased rates of weight gain and feeding ef®ciencies from the ®rst to last cycles for both WC groups was observed, and signi®cant increases was observed between cycles 4 and 5. The rate of weight gain and feeding ef®ciency of HFL was signi®cantly higher than that of the HFG group for all cycles (P`0.05). The rates of weight loss were signi®cantly decreasing with each successive cycle for HFG, but were unchanged for HFL. Percentage of body fat was not modi®ed permanently from BL to sacri®ce for both HFG and HFL groups. The body fat of HFA was higher than that of the other groups (P`0.01), while the body fat of LFA was signi®cantly higher than that of the LFR, BL and HFL groups (P`0.01), but was similar to that of the HFG and HFR groups. The body fat of WC groups and HFR were similar to each other. The percentage of internal fat (retroperitoneal omental) were similar for the WC groups. The percentage of internal fat of the HFG, HFR and LFA groups were similar, but were signi®cantly higher than that of the BL and LFR groups (P`0.05). The percentage of internal fat of HFA was signi®cantly higher than that of the rest of the groups (P`0.01). CONCLUSION: Short-term WC did not affect body fat content in these animals, but since weight gain became easier and weight loss became more dif®cult for animals in the HFG group, repeated WC may promote obesity in these rats. International Journal of Obesity (2000) 24, 236±245 Keywords: weight cycling; rates of weight gain and loss; feeding ef®ciency; body fat content Literature reviewObesity is a major health risk in the US, and it has been reported that approximately 33% of adults 20 y of age or older are overweight. 1 Many obese people who are dieting (women 50% and men 33%, 2 are able to lose weight initially, but because daily energy expenditure decreases dramatically, 3 weight maintenance at a...

Weight cycling promotes fat gain and altered clock gene expression in adipose tissue in C57BL/6J mice

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Effect of Low-Fat and/or Low-Energy Diets on Anthropometric Measures in Participants of the Women’s Diet Study

“…Our definition of "cycle" thus was limited to weight changes in the two years prior to randomization, and it was defined as at least one cycle of a gain followed by a loss or a loss followed by a gain. One such weight cycle may not be sufficient to elicit all the potentially adverse changes that have been observed in animals following multiple weight cycles noted in some, but not all, studies [12,21,22], and this is a potential limitation of our study. We could, however, compare subjects who did cycle at least once versus subjects who were of stable weight, lost weight or gained weight in the previous two years.…”

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