You might be able to blame your genes for weighing more and increasing your risk of obesity, but you can no longer blame your genes for failing to lose weight, a comprehensive study has found.
There are nearly 100 genes now connected to overweight and obesity, and there’s no question that genes can play an important role in how you break down calories and store fat. But to blame your DNA for the more difficult challenge of losing weight wouldn’t be right. That’s the conclusion of a study led by John Mathers at Newcastle University and published in theBMJ.
Obesity-related genes explain nearly 3% of the differences among people’s body mass index (BMI), a measure of weight and height. And among those, one stands out as having the strongest connection to weight among whites and African-Americans. First identified in 2007, a specific form of the FTO gene, which is involved in regulating how the body either burns calories for heat or turns them into fat, has been associated with being heavier.
Carriers of the FTO gene are known to be on average 3 kilos (6.6lbs) heavier and 70% more likely to be obese. However, researchers at Newcastle University, publishing in The BMJ today, report that in a review of eight studies involving over 9,000 people, carrying this gene did not prevent them losing weight.
John Mathers, Professor of Human Nutrition at Newcastle University, who led the study, said: "You can no longer blame your genes. Our study shows that improving your diet and being more physically active will help you lose weight, regardless of your genetic makeup."
Getting the weight off
Obesity is a major health problem and, in the UK, more than 25% of adults are obese. For some people, carrying the risk variant of the FTO gene can lead to them being heavier and increasing their risk of obesity. The FTO gene has been shown to have the biggest effect in this area.
In a major collaborative systematic review and meta-analysis, the international team used individual data from 9,563 adults who were enrolled in randomised controlled weight loss trials around the world to find out whether carrying the risk version of the FTO gene affects how much weight people lose.
They found that carrying the risk version of the FTO gene had no effect on weight loss as Professor Mathers explains: "We were excited to find that people with the risk version of FTO respond just as well to weight loss interventions as everyone else.
"This is important news for people trying to lose weight as it means that diet, physical activity or drug-based weight loss plans will work just as well in those who carry the risk version of FTO.
"For public health professionals, it means that the adverse effects of the FTO genotype on weight gain are not an impediment to weight loss interventions."
FTO gene carriers
Importantly, the team found that the response to weight loss interventions for people carrying the risk variant of the FTO gene was similar for men and women, younger and older and people of different ethnicities. However, most people in the studies were Caucasians with smaller numbers of those from Black/ African American and Hispanic backgrounds. The team say future research should explore effects of FTO on weight loss in other ethnic groups. In addition, the effects of other obesity-related genes on weight loss remain to be investigated.
In a linked editorial in The BMJ, Dr Alison Tedstone, chief nutritionist at Public Health England, says the causes of the obesity epidemic are multiple and complex, but current evidence suggests they have little to do with gene profiles.
She argues that, if we are to turn back the tide of obesity, a focus on personalised interventions based on the genome "may not pay off, at least in the short term." Instead, she says "a rebalancing of research towards whole systems approaches including environmental drivers may be of greater benefit to the population in the long term."
Among a group of nearly 9,000 people who were enrolled in 11 studies in which they agreed to genetic analysis and were randomly assigned to a variety of weight loss methods, including diet, exercise or drug-based therapies, Mathers found the answer was a surprising no.
He found that whether or not they had the weight-inducing form of the FTO gene didn’t seem to matter when it came to how much weight the people lost. While previous studies found that people with that variant were on average six to seven pounds heavier than people with other forms of the FTO gene, when it came to losing weight, there was no effect. And there were no differences among people with and without the FTO variant and their weight loss whether they tried dieting, exercise or weight-loss drugs.
“We found no evidence at all that FTO genotype affected weight loss,” says Mathers. “It didn’t affect weight loss when we simply looked at kilograms of weight lost, or BMI or waist circumference; however we looked, the FTO genotype did not seem to matter. We think this is good news — carrying the high risk [form of the gene] makes you more likely to be a bit heavier but it shouldn’t prevent you from losing weight. That should encourage people.”
The results mirror those from previous studies of people with variants of the FTO gene, who were able to counteract the effects of their DNA and avoid excessive weight gain with exercise.
The study still doesn’t answer exactly how the FTO gene contributes to weight, but researchers suspect it has something to do with appetite and people’s ability to feel full. The fact that the researchers did not find differences in people’s waist circumference, a stand-in for the type of fat that a body holds, suggests that the gene isn’t strongly related to the build up of unhealthy visceral fat which can lead to weight gain.
That means that for now, the findings “reinforce some very straight forward public health messages,” says Mathers. “No magic genes change anything in that respect. You have to bite the bullet, and eat a bit less, or be more active [to maintain a healthy weight].”
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