Their findings, published in the journal PLoS Medicine, shed more light on the relationship between genes and body weight, and could eventually help to develop treatments for obesity.
Researchers from the MRC Epidemiology Unit in Cambridge had found previously that people who were physically active could reduce the impact of ‘obesity genes’ by 40 per cent, compared with people who were sedentary.
Some studies by other scientists supported this finding, but other studies did not find that physical activity offsets predisposition to obesity.
To get a definitive answer, MRC researchers used an innovative method to re-analyse data on 218,000 adults from 45 previous studies that had looked at body weight, physical activity and a common gene called FTO which is associated with a 20–30 per cent increased risk of obesity.
They found that carrying at least one copy of the FTO gene increased the chance of a person being obese, but that the effect of the gene was reduced by 27 per cent in people classed as physically active compared with their physically inactive counterparts.
The FTO gene is common, with three-quarters of people of European and African-American descent, and 28–44 per cent of people of Asian descent, inheriting at least one copy from their parents.
Dr Ruth Loos from the MRC Epidemiology Unit and lead author of study said:
“Our findings emphasise that daily physical activity does reduce the risk of obesity, even in those who are genetically predisposed. The findings contrast with the determinist view held by some that ‘obesity is in their genes’ and they cannot do anything about it. Knowing about this interaction between genes and lifestyle could give people a sense of control. The effects are seen with 30 min of physical activity five days a week. You do not need to run marathons; cycling to work, walking the dog, weeding the garden all count.”
Professor Nick Wareham, director of the MRC Epidemiology Unit, said:
“Investigating how the interactions between genes and lifestyle contribute to obesity is an important part of understanding one of the most pressing health issues facing the UK population. The interactions may be complex, but the message is simple: there are benefits of being physically active, regardless of any genetic predisposition.”