Photo: kkielly, Flickr

Eating dinner or snacking while tuning into David Letterman and Conan O'Brien is probably not a good idea if you're watching your weight. A new obesity study indicates eating during traditional sleep times (aka. the middle of the night) can add on pounds. Your circadian clock, or biological timing system, regulates energy use, so gaining or losing weight is likely more than simply calories in/calories out.

Just published on-line in the journal Obesity, the study examined feeding times in nocturnal mice. Critters fed a high-fat diet during a 12-hour span of normal sleeping hours gained more weight than mice eating the same diet during 12 natural wake-time hours. Like us, mice love high-fat food, and the sleepy-time eaters had a 48-percent increase in weight over baseline versus a 20-percent increase for the wake-time feeders. Interestingly, while both feeding groups consumed and moved the same amount over the six-week study period, mice fed during traditional sleeping hours averaged a 7.8-percent higher fat percentage. Not fair.

This is bad news for the second and third shift, and perhaps you should re-think watching late night TV with a plate of nachos in your lap. Whether you're a vampire-eater or not, total food intake and obesity are intertwined. Stay away from the late night barbecue tonight, and keep counting those calories and writing them down.