Hunger games: The effects of alternate day fasting on food intake, body weight, and leptin and ghrelin in rats

PURPOSE: To determine whether a compensatory increase in food intake occurs following a day of fasting, and to determine whether leptin and/or ghrelin levels change in response to ADF compared with ad libitum feeding.;INTRODUCTION: Recently, alternate-day fasting (ADF) has grown in popularity as an alternative to continuous energy restriction (CER) diets as a method for improving health and controlling food intake. Leptin and ghrelin are two hormones implicated in the regulation of food intake and body weight, however their response to ADF is unclear.;METHODS: Male Wistar rats of the same age and weight were randomly assigned to the ADF group (n=7) or a control group (n=7). The ADF group had alternating 24-hour fasting and feeding days for 30 days. Fasting rats were limited to 3-5g of regular chow on fasting days and were given food ad libitum on feeding days. The control group had food ad libitum everyday for the same 30 days. Food intake for each animal was measured on a digital scale and recorded daily, and body weight was measured weekly. 600 mul blood was taken from the tail of each rat at the end of day 1, day 2, day 29, and day 30, to measure hormone levels after a fasting and feeding day before and after the ADF intervention trial. Leptin and ghrelin levels were determined by radioimmunoassay.;RESULTS: Food intake by ADF rats was increased by 20% on ad libitum feeding days (F =3.484, p = .047), however ADF rats had lower rates of weight gain compared to the control group (290 g vs 355 g; F = 41.604, p < .001). Total percent body fat was significantly higher in the ADF group compared with the control group (19.9% vs 15.6%; t = -2.848, p = .015). Diet had no significant effect on leptin and ghrelin levels.;CONCLUSION: Results of this study indicate that food intake on feeding days did not sufficiently increase to offset the calorie deficit incurred on fasting days. Despite a decrease in weight gain, percent body fat increased in the ADF group. This may be the result of an adaptive change in the use of energy from growth/production to body maintenance and repair.