From Featuring Dr Chris Steele MBE

Most surprising weight loss tip

Live with a fat person to stay slim

There is much debate about the true causes of the recent rise in obesity levels in rich countries. It is particularly difficult to separate the effects of genetics and our environment. Now a new study has discovered a surprising outcome - living with an overweight person can help reduce our own weight gain.

The study looked at the effect of college room-mates on students' weight gain in the first year. First year college students are of interest because they typically gain weight over the year - thought to be a consequence of changed eating and living habits associated with being on their own for the first time.

Effect of room-mate's weight

Surprisingly, students who were assigned an overweight room-mate were found to have significantly less weight gain than those assigned to a slimmer one - half a pound versus 2.5 pounds.

"This finding seems counterintuitive, but there are some good explanations for why it may be happening," said study author Kandice Kapinos, an assistant research scientist at the University of Michigan Institute for Social Research.

Heavier students are more likely to diet, and typically exercise more and are more likely to use weight-loss supplements. "It's not really the weight of your room-mate that's important, but the behaviours your room-mate engages in," Ms Kapinos said. "These behaviours are what may really be 'contagious.'"

Surprising result

The results are surprising because previous studies have suggested that having an obese spouse, friend or sibling increases one's likelihood of becoming obese. But these relationships are not random - relatives share our genetics and we chose friends and partners because they share common interests and outlooks. Students are normally assigned a room-mate by the college authorities, so the choice of whom they live with is essentially random.

Another part of the study found that students in accommodation with on-site dinning areas gained more weight that those who had to go outside to get food.

"Our hope is that this line of research will have practical implications for university administrators and more generally for public health efforts aimed at reducing obesity," Ms Kapinos said.

The study was presented at the annual meeting of the American Society of Health Economists.

This article was published on Wed 22 September 2010