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When It Comes to Obesity, Genes Just Partly to Blame

THURSDAY, Oct. 26, 2017 -- If you have trouble keeping slim, don't put all the blame on your DNA.

People carrying so-called "obesity" genes tend to gain more weight if they don't work out or don't get enough sleep, said Timothy Frayling, a professor with the University of Exeter Medical School in England.

"You can't change your genes -- but they only explain part of your weight," Frayling said. This means that even people genetically inclined to pile on pounds can curb it by eating right and exercising.

Frayling and his fellow researchers tracked physical activity and sleep patterns for about 85,000 people in England, aged 40 to 70. The participants wore accelerometers that allowed researchers to estimate their amount of exercise and quality of sleep.

The team also computed a genetic risk score for each person based on 76 common variants known to be associated with increased risk for obesity.

Genetics accounted for some, but not all, of a person's obesity risk, the researchers concluded.

For example, a person of average height who had 10 genetic risk factors for obesity gained an average of 8 pounds during the course of their life if they tended to be couch potatoes, but only about 6 pounds if they were more physically active, the study authors said.

The results were similar regarding sleeplessness. People with some genetic risk for obesity tended to have a higher body mass index (BMI) if they woke frequently or slept more restlessly, the study findings showed. BMI is a measurement of body fat based on height and weight.

"For public health and diet and exercise interventions, our study suggests there will be 'bigger bang for the buck' by focusing limited resources on people who are most susceptible due to their genes and their lifestyles," Frayling said.

Obesity experts said the study results make sense, given what's known about the factors that contribute to excess weight.

"Obesity is an energy storage disease that is caused by hormonal imbalances," said Dr. Mitchell Roslin, chief of obesity surgery at Lenox Hill Hospital in New York City. "Your genetic makeup plays a role, but your activity and the environment also influence your genetic expression," he explained.

"Many believe that obesity is an epigenetic disease, meaning it is not the genes themselves but how the environment changes their shape," Roslin continued. "Think of genes as pieces in a jigsaw puzzle. The environment puts the puzzle together. Our actions matter, and while our genes influence our behavior, our behavior influences how genes work and their effect on the body."

Dr. Jamie Kane, chairman of the Center for Weight Management at Northwell Health's Syosset Hospital in Syosset, N.Y., said the study "seems to ring true based on the research that's out there to date, and based on my clinical experience as well."

Kane and his staff try "to look at the lifestyle, and work at the most stringent level with patients because we don't know who has what genetics," he said.

It might require more dedication, but a person can overcome genetics that might otherwise lead to obesity, Kane concluded.

"There are a very small number of people who suffer from morbid obesity where it's purely genetic," he said. "In most of these cases, people might need to exercise way more than the average person, and they might need to change their diet dramatically."

Frayling and his colleagues presented their findings this week at the annual meeting of the American Society of Human Genetics, in Orlando, Fla. Research presented at meetings should be viewed as preliminary until published in a peer-reviewed journal.

More information

The Harvard T.H. Chan School of Public Health has more on the genetics of obesity.

Posted: October 2017

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