Effect of Sleep Restriction on Metabolic Disturbances Caused by Overfeeding

General hypothesis : In overfeeding condition, the stress response generated by partial sleep restriction of six days will induce an accumulation of fat in the liver and a decreased insulin sensitivity of adipose tissue , liver and muscle, more pronounced that in overfeeding condition only, provoked by a deregulation of the nocturnal lipolysis . Specific goals : Purpose 1 : To measure the accumulation of fat in the liver (measured by nuclear magnetic resonance ) and the tissue insulin sensitivity ( measured by a test meal ) in response to a sleep restriction in overfeeding condition . Hypothesis 1: In overfeeding condition (130 % of energy requirements ) , hepatic lipid accumulation will be higher after 6 days of sleep restriction (4 hours per night) compared to a control condition (8 hours of sleep per night ) . Decreased sensitivity to insulin in the liver, adipose tissue and the associated muscle will be associated at this ectopic fat accumulation. Purpose 2 : To determine the alteration of lipolysis in response to sleep restriction in overfeeding condition. Hypothesis 2: In overfeeding condition, sleep restriction will increase the concentrations of circulating fatty acids and glycerol in relation to condition of normal sleep.