Study Finds Strong Genetic Component to Obesity

A new finding by the Genetic Investigation of Anthropometric Traits, or GIANT, consortium has identified 97 gene regions associated with obesity, tripling the number of such genes previously known. The study, which stands as the largest genome study conducted to date, was led by Harvard Medical School professor Joel N. Hirschhorn.

According to University of Michigan assistant professor Elizabeth K. Speliotes, the consortium is a "group of investigators that are trying to understand the basis of anthropometric traits,” which includes statistics such as human height, weight, and waist-to-hip ratio.

This medical advancement did not come without time and effort. Ruth J.F. Loos, professor for preventative medicine of Mount Sinai Hospital in New York, said the study has been in the works for many years.

“It took us about four years to combine even more data and that is what was published recently,” she said. According to Loos, the paper is the most recent in a series of publications and represents the work of 125 studies, which used about 340,000 individuals as subjects.

Many of the gene variants were located in the brain, meaning that many of the genes regulated processes such as hunger and energy expenditure. “Obesity is more of a central nervous system disease,” Loos said.

Speliotes said that “our work clearly shows that predisposition to increased BMI is not due to a single gene or genetic change. We report 97 genome-wide hits but we show data that even more regions of the genome are likely to influence the trait. This suggests that different people may be predisposed to become obese by different mechanisms.”

Despite the strong influence of genes in obesity, the environment can play as strong a part. According to Loos, only 40 to 70 percent of the variation in obesity is caused by genetics. The remaining 30 to 60 percent can be attributed to the environment you live in. “We definitely do not claim that it is destiny,” she said.

For Cecilia M. Lindgren, scholar in residence at the Broad Institute of MIT and Harvard and a professor at the University of Oxford, the GIANT consortium marked an important shift towards collaboration in genetics research. Lindgren also noted that genetics is especially suited to large scale collaboration.

“When I started my Ph.D.… nobody was in consortia,” Lindgren said. “[But] in order to test [genetics data] robustly, you have to have really a large sample size. Now I think we have over five hundred authors on these papers… and over 300,000 individuals. I do think that collaboration is kind of the key to the future.”

—Staff writer Melanie Y. Fu can be reached at mfu@college.harvard.edu. Follow her on Twitter @MelanieYFu.

—Staff writer Jiwon Joung can be reached at joung@college.harvard.edu. Follow her on Twitter @YunaJoung.