It is time to scratch another excuse off the list of reasons you can’t lose weight: According to a new study, improving diet and getting more exercise helps people lose weight—regardless of their genetic makeup.
Yes, there is a so-called “obesity gene.” People who carry a specific variant of the FTO gene have been shown to be an average of 6.6 pounds heavier than those who don’t, and are 70% more likely to be obese. But when researchers at Newcastle University in the United Kingdom compared people who had the FTO gene variant with those who didn’t, they found that it had no effect on how well participants responded to weight loss interventions.
In other words, said co-author and professor of human nutrition John Mathers, PhD, in a press release, “you can no longer blame your genes.”
The new report, published in BMJ, is a scientific review of eight previous studies from around the world, involving more than 9,500 people in total. All eight studies were randomized, controlled trials of weight loss plans that included diet, exercise, medications, or some combination of the three.
When the researchers combined and re-analyzed results from all of the studies, they found that changes in body mass, weight, and waist circumference were not significantly different between people with different FTO variants.
They also found no differences between gene types when they looked at results based on gender, ethnicity, age, or the type of weight loss intervention. (They do point out, though, that most study participants were Caucasian, and that more studies should be done on more diverse groups.)
These findings contradict those of a 2012 review including some of the same studies, which found a small genetic influence on weight loss efforts. But, the researchers say, the new analysis included more participants and more individual data, and they only looked at studies that carefully ruled out or controlled for potential factors that may have influenced the results.
“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,” Mathers said.
It also suggests that a genetic predisposition to obesity “can be at least partially counteracted through such interventions,” the authors wrote.
While the FTO variant seems to play the largest genetic role in a person’s weight, it’s not the only gene that’s been implicated in weight gain or obesity. The gene IRX3, for example, has been found to also play a role in regulating body mass, and a variant of the MC4R gene may make people more prone to overeating.
The authors acknowledge that their study only looked at one obesity-related gene, and that the effects of others are still unknown.
But many experts say that in the grand scheme of things, genes—all of them—likely play a very small role in obesity. In an editorial published with the new study, Alison Tedstone, PhD, writes that “the causes of obesity are multiple and complex,” and that the Newcastle study adds to evidence “suggesting that environmental factors might dominate over at least common obesity-linked genes.”
Tedstone, who is chief nutritionist at the government organization Public Health England, also writes that weight-loss programs marketed as being customized based on a person’s genome “may not pay off, at least in the short term.”
Instead, she says, obesity research should focus on “whole systems approaches” including environmental causes and solutions, in order to benefit more people of all genetic makeups.