Understanding thinness may be key to fighting obesity, eating disorders, VCU study finds

By Joe Kuttenkuler

RICHMOND, Va. – Heredity, as opposed to social and environmental factors, largely determines why some people stay thin while others get larger, according to a new study by Virginia Commonwealth University.

The study, conducted over 10 months by a team of researchers at VCU’s Virginia Institute for Psychiatric and Behavioral Genetics, concludes that about 68% of a person’s tendency to remain thin is controlled by his or her genetic makeup.

"If we can figure out the biology behind what keeps people thin, we might be able to use that information to prevent and treat obesity and eating disorders," said Cynthia Bulik, Ph.D., associate professor of psychiatry in VCU’s School of Medicine and an expert on eating disorders. "So much is being done to discover why people are becoming obese, we decided to take the opposite approach and look at factors that keep people thin."

Rates of obesity have steadily risen for the last 20 years, and even moderately overweight individuals are at risk for developing a variety of health problems. According to the Centers for Disease Control, the prevalence of overweight Americans – those with a body mass index between 25 and 29.9 – nearly doubled between 1980 and 2001, to 50% of the population, and the number of obese Americans (BMI greater than 30) reached 25% of the population.

BMI is a measure of weight to height, with 18.5 to 24.9 being normal, 25 to 29.9 being overweight and over 30 considered obese.

To determine the extent to which genes influence thinness, Bulik and VCU professors Patrick F. Sullivan, M.D., associate professor of psychiatry, and Hermine Maes, Ph.D., assistant professor of human genetics, surveyed 7,829 twins with normal and obese BMIs from VCU’s Mid-Atlantic Twin Registry.

They examined the magnitude of genetic effects and environmental factors on thinness and found that – like for obesity – genetics is the primary force that helps a person stay thin, regardless of socioeconomic status or other common environmental factors.

"Thinness is a very good model in helping us understand body weight regulation," said Bulik. "The next step is to support research to identify the genes that contribute to a person’s tendency to remain thin."

The study will be presented during the International Conference on Eating Disorders in Boston April 25-28.