To investigate whether intermittent fasting alters subsequent utilization of ingested energy, we compared, in six groups of 450-g male Wistar rats, two modalities of food delivery: constant (CO) vs fasting for 3 days and refeeding for 7 days (F/RF). Both modalities were investigated at three planes of nutrition (100, 60 and 40 percent of ad libitum). The F/RF groups were offered, during the 7 days of refeeding, the same amount of food as the CO groups were offered in 10 days. With both 60 and 40 percent food restriction, there were no differences in body weight, body composition, or energy utilization between the F/RF and the CO groups after 4 (40 days) or 8 (80 days) cycles of fasting-refeeding. However, at both 40 and 80 days of study, lipoprotein lipase (LPL) activity was significantly higher in F/RF rats than in CO rats at all three planes of nutrition. Because 100 percent F/RF rats did not eat all food available during each refeeding period, a second experiment was conducted. Rats were fasted for 3 days then refed ad libitum until they reached the weights of 100 percent CO rats. The two groups did not differ in body weight, food intake, body composition or LPL activity after 4 (40 days) fasting-refeeding cycles. Thus, weight cycling produced by repeated bouts of fasting-refeeding did not result in increased efficiency of energy utilization. However, the combination of fasting-refeeding and overall caloric restriction produced greater LPL activity than constant food restriction. It has not been determined whether this elevated LPL activity would affect lipid accumulation upon ad-libitum refeeding.
