It sounds like an even more cruel take on hanging out with a less attractive friend when you were a teenager so you'd be more popular and get asked out on more dates. But when it comes to avoiding weight gain, having a fatter flatmate isn't as cruel an idea as it first seems.
The researchers decided to investigate a phenomenon in the US called 'Freshman 15' (the figure refers to the amount of weight in pounds that students starting college are typically thought to gain during their first year living away from home).
What the researcher team found was that female students with roommates who weighed more than average gained less weight during that first year at college than women who had slimmer roommates.
The reason, they suggest, is that if your roommate has a weight problem she may be more likely to diet and exercise in an attempt to shed pounds - all of which could have a knock-on effect on you too.
So if the research is correct, your flatmate being a bit on the podgy side might encourage you to eat more healthily and be more active. Well, that's the theory anyway.
What do you think? Are the researchers barking up the wrong tree, or could there be some truth in their findings?