BACKGROUND: There is a window of opportunity for the overnight period where pre-sleep protein intake yields favorable benefits. Previous studies report that dietary protein consumption prior to sleep is fully digested and absorbed by the body, thereby stimulating overnight muscle protein synthesis, and increases resting metabolism the following morning compared to placebo in college-aged men. However, little is known about how pre-sleep feeding effects the female population or how whole foods influence metabolism the following morning compared to a liquid supplement. PURPOSE: To investigate the extent to which consumption of cottage cheese (CC) effects next-morning resting energy expenditure (REE) and appetite compared to isocaloric casein protein (CP) and a non-energy containing placebo (PL) when consumed before sleep in active, college-aged females. METHODS: In a randomized, partially-blind, crossover design, ten active females (age, 23.1 ± 1.8 yrs; body fat, 22 ± 4.6%) ingested either pre-sleep CC (160 kcals, 30g protein, 10g carbohydrate, 0g fat), CP (160 kcals, 30g protein, 10g carbohydrate, 0g fat) or PL (0 kcals) ~30 min before sleep. To maintain exercise regimen throughout the study, participation in physical activity took place every other day to exclude the 24 hours leading up to an experimental visit. All participants were tested during the follicular phase of their menstrual cycle. Participants slept overnight in the laboratory and upon waking the next morning (0500-0800), measurements of REE and subjective measures of satiety, hunger, and desire to eat were recorded. Statistical analyses were conducted using a one-way ANOVA for metabolic variables and changes in appetite. Significance was accepted at P < 0.05. All values are reported as means ± SD. RESULTS: There were no significant differences in acute and next morning REE as well as no differences in sleep quality, RER and measures of hunger, satiety and desire to eat the following morning across treatments. CONCLUSIONS: In college-aged, active females pre-sleep consumption of 30g of protein (160kcals), from either cottage cheese or casein protein, is not metabolically different than consuming a non-caloric placebo. These results suggest eating at night pre-sleep does not hinder next morning metabolism.
