Researchers Identify Genes Linked to Obesity and Body Fat Distribution
Although lifestyle factors are primarily involved in the development of obesity, whether a person is more likely to gain weight in the abdomen or in the hips and thighs is largely determined by genetics. Researchers from the UK have identified more gene variants linked to obesity and body fat distribution, which may help lead toward new dietary advice or medicines to fight the obesity epidemic.
Understanding biology is a vital first step in a long journey towards treatment
Ruth Loos, group leader in the Genetic Aetiology of Obesity Program at the Institute of Metabolic Science in Cambridge, and colleagues conducted two studies. The first, a meta-analysis of data from 46 gene studies, identified genetic variants linked to body mass index (BMI). In all, the studies included over 120,000 people. Loos’ group found 18 new genomic regions associated with weight status and confirmed 14 other previously identified regions.
The genes appear to act in the brain, said Loos. “This suggests that these genes may act through increased food intake – maybe appetite and reward.” But she warns that having a genetic tendency does not eliminate the lifestyle factors that contribute to obesity, such as diet and exercise. “You still need the environment on top of that to really trigger that susceptibility,” she said.
In the second analysis, Loos and colleagues analyzed 32 genome studies (77,167 participants) associated with hip to waist ratio, a measure of fat distribution. The team identified 13 gene variants that appeared to influence the distribution of fat, or whether someone gained weight in the abdomen (“apple” shape) or in the hips and thighs (“pear shape”). Among these, seven had a stronger effect on women than men.
Body fat in the abdomen, also called visceral fat, is more heavily associated with chronic health conditions such as heart disease and diabetes. The newly discovered genes are known to be involved in controlling cholesterol, insulin, and insulin resistance.
Although the genes cannot predict whether a person will become obese or not, Loos noted that the more of the gene variants that a person has, the greater their susceptibility to obesity. The average person has about 28 to 32 variants, while about 2% of the population carries more than 38, causing them to be (on average) 15 to 20 pounds heavier than those who had fewer than 22 such variants.
"Understanding biology through finding genes is just a first step in a long journey towards treatment, but it is a vital one,” said Dr. Cecilia Lingren of the Wellcome Trust Centre for Human Genetics at Oxford University. Loos added, “If we know the biology, perhaps we can invent a more effective preventive strategy. Maybe we can identify proteins that we can target with drugs." Loos said.
But Loos also noted, "It's going to take years before these new discoveries will develop into new interventions." Therefore, it is important to continue to eat a healthful, reduced calorie diet and increase physical activity to shrink fat cells.
"Meta-analysis identifies 13 new loci associated with waist-hip ratio and reveals sexual dimorphism in the genetic basis of fat distribution."
Iris M Heid, Anne U Jackson, Joshua C Randall, Thomas W Winkler, Lu Qi, Valgerdur Steinthorsdottir, Gudmar Thorleifsson, M Carola Zillikens, et al.
Nature Genetics, Published online: 10 October 2010