NEW YORK (Reuters Health) - People's tendency to choose mates with body sizes matching their own could be one factor driving the current obesity epidemic, according to a new study.

Obese people are more likely to marry other obese individuals, while children of two obese parents are at 20-fold risk of being obese compared to offspring of two lean parents, Dr. Peter Jacobson of Sahlgrenska University Hospital in Goteborg, Sweden and colleagues report. The researchers also found that lean people were more likely to marry other thin people.

Both genetic and environmental factors are believed to contribute to obesity, according to Jacobson and his team. Attention has focused on modern lifestyle factors that promote overeating and sedentary habits, but genes that predispose people to obesity might be expected to become increasingly common if people carrying these genes tend to have children together.

To investigate, the researchers looked at information on spouses and families of 7,834 obese people and 829 people randomly chosen from the population, including a total of 8,663 couples. People at either extreme of the body mass index (BMI) spectrum were more likely to marry others of the same body size, the researchers found.

And among adults with two obese parents, 20.1 percent were obese, compared to 8.2 percent of those with a single obese parent and 1.4 percent of people with two lean parents. While pairs of obese individuals represented just 16 percent of the couples in the study, they accounted for 35 percent of the obese offspring.

Identifying the BMI of both of a person's parents could provide a "powerful" way to spot those who will benefit the most from obesity prevention programs, the researchers conclude.