People make all kinds of excuses for being a little overweight. But a new study suggests that tensions between our biological clocks and enforced working hours could be making us all pile on the pounds.

We humans are creatures with natural, biological tendencies to work and sleep at certain times—and we're all slightly different. Researcher Till Roenneberg explains to Live Science:

"We are biological beings, and we have a biological clock, and what society - and I don't mean the bad guys, I mean all of us - is ignoring is the biological clock. We think we can do whatever we want with the social clock."

In fact, Roenneberg's new study suggests that the problem is that we all favour waking and sleeping at subtly different times—something that isn't accounted for by enforced business and social schedules. For those whose natural body clocks disagree most with their enforced routines, the result is extra weight.

Roenneberg and his colleagues studied data from more than 65,000 people, looking at their waking and sleep behavior during work and free days. The results, which are published in Current Biology, indicate that for each hour of sleep discrepancy between their natural preferences and enforced routine, people are 33 percent more likley to have a higher Body Mass Index. The likely explanation is that interference with natural waking hours messes with metabolism, in turn making us put on weight.

In days past, our lives were dictated by our body clocks, but nowadays that's virtually impossible to achieve. Instead, Roenneberg suggests that the solution is to try and negotiate with your employer to make your working hours fit your natural rhythms more closely. Good luck with that. [Current Biology via Live Science]

Image by eflon under Creative Commons license