Bad Idea: Don’t weight up

So it looks like it might not be the biscuits, after all. A new report suggests that if you're under 40, and you usually get less than five hours' sleep a night, you're likely to get fatter, quicker, than someone who has a decent kip on a regular basis. And it's not just any fat, but the worst, most unhealthy kind: visceral fat is the type that bunches menacingly around the internal organs like a group of troublemaking bullies ganging up on a classmate.

“We put a lot of stock in diet," explains Kristen Hairston, lead researcher on the report. Based at Wake Forest University, North Carolina (the proud home of Pepsi-Cola, pork barbecue and Krispy Kreme doughnuts), Hairston suggests that "we may need to start looking at other behaviours", too.

Sadly, regular lie-ins are not the answer: the researchers found similar, if less pronounced, weight gain among those who sleep more than eight hours a night. But it's definitely worth trying to avoid being poor. Hispanic men and black women - two of the poorest demographics in the US - were the most sleep-deprived. Not surprisingly, those working several jobs to make ends meet were also at risk.