A lack of sleep can contribute to obesity by increasing the appetite in men and preventing women from feeling full after a meal, a study has found.
An experiment on 27 healthy volunteers found that restricted sleep affected levels of different hormones in men than in women.
Scientists have thought that long-term sleep deprivation may contribute to obesity because it increases the number of calories eaten the following day.
It has now been found the mechanism for this differs between the genders.
Lead author Dr Marie-Pierre St-Onge, of the Columbia Medical Centre, said: "Restricting sleep in healthy, normal weight participants has limited effects on metabolic risk factors and may affect food intake regulating hormones differently in men and women.
"We were surprised by the lack of a significant effect of sleep on glucose and insulin, leptin, and sex differences in the hunger-stimulating hormone ghrelin and the satiety hormone GLP-1."
The findings were published in the journal Sleep.
The team measured hormone levels in the blood taken from the volunteers after sleeping for four hours and for nine hours.
Short sleep increased total ghrelin levels in men but not women and reduced GLP-1 levels in women but not in men, a sex difference that has not been reported before.
The results suggest that the common susceptibility to overeat during a period of short sleep is related to increased appetite in men and reduced feelings of fullness in women.
Dr St-Onge said: "Our results point to the complexity of the relationship between sleep duration and energy balance regulation.
"The state of energy balance, whether someone is in a period of weight loss or weight gain, may be critical in the metabolic and hormonal responses to sleep restriction."
Rebecca Smith Telegraph.co.uk