Sleep deprivation can lead to weight gain or limit the beneficial effects of a reduced calorie diet on total body adiposity. Reduced sleep duration has become a common aspect of the westernized lifestyle defined by physical inactivity and overeating.
A few recent studies (see details below) tie reduced sleep to obesity but little is known on the regulations underlying. Longer lasting prospectif and interventional studies are needed to understand the mechanisms responsible. It might be as simple as the fact that you cannot eat while sleeping?
Does sleeping longer makes you thinner?
One presentation studied healthy overweight volunteers (mean age 40 years, mean BMI 27.5). The subjects completed two 14-day studies at least 3 months apart; during which they spent either 5.5 hours or 8.5 hours in bed per night. During both study periods, they consumed a nutritionally balanced caloric intake equal to 90% of their resting metabolic rate, and weight loss during each treatment was similar (mean 3.0 vs 2.9 kg, respectively).
However, fat represented only 26% of the weight loss during sleep restriction as compared with 57% during the 8.5-hour bedtime condition (p = 0.031), indicating increased loss of lean body mass during reduced sleep conditions.
In another study, 92 healthy adults (22 to 45 years old) spent 2 nights of unrestricted sleep (10 hours time in bed), followed by 5 nights of 4 hours time in bed. Nine control subjects spent 10 hours/night in bed during the 11-day protocol. Sleep restricted subjects experienced a mean weight gain of 1.31 kg during the protocol (p < 0.0001), even though they reported decreases in appetite, food cravings, and food consumption. There was no significant weight gain in the control group.
During real-world periods of sleep restriction ... keeping up regular exercise is just as important as what food you eat, so even though people may feel tired, exercising will help regulate energy intake balance."
Source: presentations at SLEEP 2009, the annual meeting of the Associated Professional Sleep Societies