A new study says that eating at irregular intervals or at wrong hours might lead to an increased waistline.

A research done on mice showed that a group of them fed with a high-fat diet during sleeping hours gained more weight as compared to another group that was given the same type of food during natural waking hours. Both these groups had similar activity levels.

Findings reported online in the journal Obesity suggest that the reasons of weight gain are complicated and unclear.

"How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out," said study co-author Fred Turek, director of Northwestern's Center for Sleep and Circadian Biology, in a statement.

Researchers suggest that eating midnight meals disrupt the body's circadian clock thereby causing weight gain. The circadian clock controls the body temperature and levels of certain hormones, which gets disturbed with irregular eating habits.

The study's lead author, Deanna Arble said that studies in people have already shown associations between weight gain and irregular eating patterns, such as skipping breakfast.

More research needs to be done to clearly identify the exact mechanism at play.