To lose weight it's a matter of simply eating less and exercising more, right? But that's not all. You need to sleep well too, say US experts.
It's not the first time scientists have claimed sleep is important for weight loss. But this study goes a step further and suggests sleep is essential for losing body fat as well as for appetite control.
The researchers discovered when dieters had a decent amount of sleep, more than half the weight they lost came from losing fat - something every dieter knows is crucial.
But by cutting back on sleep, the amount of fat they lost was halved. The dieters also felt hungrier when they were getting less sleep, despite having the same amount of food as when they were allowed to sleep more.
So if you're trying to lose weight but you're not getting as much sleep as your body needs, it could explain why the pounds aren't dropping off.
It's all a matter of keeping down levels of a hormone called ghrelin, say the researchers. High ghrelin levels have been shown to make you feel hungry and help your body hang on to fat, as well as reduce the rate at which you burn calories.
And according to this latest study, the less sleep you get, the higher your ghrelin levels become. So when the dieters slept for an average of 7 hours and 25 minutes, their ghrelin levels weren't affected. But when sleeping for just 5 hours and 14 minutes, their ghrelin levels went up.
Why do you think so many people find it difficult to lose weight? Is sleep really an issue?