After a night of sleep deprivation the men's ratings of hunger and ghrelin levels were higher than after the night when the men got sufficient sleep. Before and after breakfast on both occasions the men where shown pictures of 13 foods, including 7 meals and 6 snack foods, and were asked to chose their ideal portion sizes. After the night of sleep deprivation the men chose larger ideal portions of the foods before breakfast. Following breakfast the ideal portion size for meal items did not differ between the two sleep conditions, but the men selected larger ideal portions of snack foods after the sleep deprivation condition.
The researchers suggest that there are two ways sleep deprivation could increase food consumption. In the first, people eat more to make up for the additional energy expenditure associated with being awake all night. In the second, sleep deprivation appears to increase the sensitivity of the brain's reward system to high-calorie foods.