Cohabitation increases your chance of getting fat, a study conducted by a U.S. nutritionist indicates.

Penny Gordon-Larsen of the University of North Carolina says there are positive health benefits to living together but remaining slim apparently isn't one of them, The Daily Telegraph (Britain) reported Friday.

Gordon-Larsen found the risk of obesity rises the longer people live together.

"Maybe the cause of weight gain is not just age, but the pressure of shifting behaviors that result in weight gain," she writes in a study to be published next month in the journal Obesity.

Gordon-Larsen says people who live together tend to eat meals together and watch television together instead of going to the gym or playing a sport.

Her research found couples living together for more than two years were most likely to display similar obesity patterns and physical behaviors.