The secret of staying thin could be at least partly down to a good night's rest, an international conference on obesity heard in Amsterdam on Thursday.
"After a bad night's sleep, people ate 550 calories (22 percent) more than normal," said the findings of a study by the European Centre of Taste Science in Dijon in central France, presented at the gathering.
This represented about one large hamburger.
Feelings of hunger were higher among a test group who slept four hours the previous night than among those who slept eight hours, stated an extract of the findings.
"These results indicate that sleep deprivation increases food intake and... could be a factor promoting obesity," it added.
A separate study conducted by researchers at the Netherlands' Maastricht University found that children who got less sleep during puberty than when they were younger also gained more weight compared to children whose sleep patterns did not change.
The World Health Organisation estimates that in 2005, about 1.6 billion adults were overweight, of which at least 400 million were obese.
The conference was organised by the European Association for the Study of Obesity.