Metabolic consequences of weight cycling induced by high fat and protein feedings in female Sprague-Dawley rats

In this study, we examined the effects of weight cycling (WC) on blood substrate, hormone levels and hepatic enzyme activities. WC in female Sprague-Dawley rats was produced by feeding them a high fat diet (HF) to induce obesity and then feeding them restricted amount of casein (3g/day) until body weight reached the control level. This weight gain/loss was repeated 3 times in HF ad-libitum fed rats (HFAL-C group). Rats in another group also weight cycled three times. During the refeeding phase, only 75% of the ad-lib intake of the HF diet was given to these rats (HF75-C). HFAL-NC group was fed the HF diet ad-libitum without any weight cycling. The control rats were fed the low fat rodent diet ad-lib and not cycled (CHAL-NC). After 61 weeks on these feeding regimens, all rats were sacrificed in a non-fasting state. It was observed that WC did not reduce final body weight or total fat content, but it reduced fat free mass compared to noncycled rats. The reduction of HF feeding to 75% reduced body weight of the HF75-C group to the level of the control rats. However, these rats still had a higher body fat content than the CHAL-NC group. Blood glucose and cholesterol levels were not different among the 4 groups. HF feeding significantly elevated blood insulin levels in HF groups, regardless of WC or not. Blood triglyceride levels, on the other hand, were affected by the quantity of energy consumed, rather than by the dietary fat content. Hepatic enzyme activities were not affected by WC or HF feeding. We concluded that WC exerted more influence on body composition than on metabolic parameters in Sprague-Dawley rats.