Outrunning the fat gene
Pippa Wysong | May 17, 2016Moderate physical activity blunts the effects of a key gene known to cause obesity, according to recent research out of McMaster University. This is good news for people who are prone to being overweight because it runs in the family. It shows your genes are not your destiny, says McMaster human geneticist David Meyre, and that often their effects can be modulated by lifestyle choices. Meyre and his team published a study this year showing just how much of an effect varying levels of exercise have on the activity of several obesity genes. To do this, he and his colleagues looked at the genetics and exercise history of 17,400 people from six ethnic groups from 17 countries. The researchers used data from EpiDREAM, a large international study designed to investigate the interplay of environment (such as lifestyle choices) and genetics on people at risk for developing diabetes. It was launched by researchers at McMaster in 2006. Meyre's team focused on the participants’ self-reported activity levels, genetic predisposition to obesity, body mass index (BMI) and body adiposity index (BAI). The BAI is a relatively new measure used to determine the amount of body fat a person has. Not surprisingly, those who were more physically active had, in general, lower BMI and BAI readings, both at the start of the study and three years later. The researchers also analyzed the mutated form of 14 different genes known to play a role in obesity, and how each was related to participants' obesity and exercise. Of the genes analyzed, they found that people with any of four particular genes (FTO, CDKAL1, TNN13K and GIPR) were more likely to be obese. But what was intriguing was that people who had one particular gene, FTO, had a bigger response to exercise. In fact physical activity decreased the impact of the mutated FTO gene on BMI and BAI by up to 70 per cent — a much stronger effect than exercise had on people who had any of the other genes studied. The study shows that physical activity can combat genetic risks. Gene linked to appetite The mutated FTO gene was discovered in 2007 and is known to be associated with early-onset and severe obesity. This gene occurs in about 22 per cent of people who are prone to obesity and is believed to have a role in modulating appetite. People with one mutated form of FTO are generally about 1.5 kg heavier than their counterparts with normal versions of the gene. But if they have two of the genes, they are about 3 kg heavier. The take-home message from Meyre's study is simple: “Exercise is good for everybody, but it is even more beneficial for this particular subgroup – people with the mutated FTO gene. They lose more weight from physical activity than those whose obesity was associated with other genes,” he says. How much exercise? “Even with one hour a week of something like jogging, these people get a benefit,” he says. Meyre argues that people would benefit from knowing whether or not they have specific genes predisposing them to obesity. If people know how much exercise they need to do, they would be more likely to stick with it, he says. Even better, they could use exercise to prevent packing on the pounds in the first place. Once a person puts on extra weight, “the body works to try to replace those cells, to restore equilibrium,” says Meyre. This is why keeping weight off is so difficult. “The best way to eradicate obesity is to prevent it,” he says.