Loos noted that the more of the gene variants a person has, the greater their susceptibility to obesity. These variants are inherited from both your mother and your father, so you can have as many as 64 variants, she explained.
The average person has about 28 to 32 of these variants; about 2 percent of the population carries more than 38 variants and 2 percent of the population carries less than 21, Loos added.
These genes appear to act in the brain, Loos said. "This suggests that these genes may act through increased food intake -- maybe appetite and reward," she said. "But you still need the environment on top of that to really trigger that susceptibility."
Over the past 30 years, the obesity epidemic has exploded, Loos pointed out. "Our genes haven't changed, our environment has changed," she stated.
However, Loos added, there are several genes whose variants are linked to extreme obesity.
In a second meta-analysis, Loos and colleagues looked at 32 genome-wide studies for genes associated with hip-to-waist ratio, which is a measure of fat distribution. These studies included 77,167 people.
The researchers identified 13 genes associated with hip-to-waist ratio that had not been identified before. Among these genes, seven had a stronger effect on women than men.
These findings show that there are sex-specific genes that regulate fat distribution. Moreover, these genes and the ones in the first study don't overlap, suggesting that different genes regulate BMI and fat distribution.
The differences between where men and women store fat -- men on the waist, women on the thighs -- is likely genetically driven, Loos said.
Obesity expert Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine, said "that there are genes as
All rights reserved