Twice the exercise needed for those at highest obesity risk

People who are genetically pre-disposed to putting on weight need to do twice as much exercise as those with the lowest genetic risk of obesity for the same result, a study has found.

It is well known that genes play a key role in obesity, with studies variously putting their contribution at 40 to 70 per cent of weight gain.

Now, for the first time, scientists have quantified what these genetic differences mean for the amount of exercise we need to do to keep our weight down.

Previous research has found that walking about 8,000 steps a day substantially reduces the risk of obesity. But that does not take into account a person’s genetic risk of obesity.

Researchers from Vanderbilt University Medical Centre in Nashville, US, followed 3,124 participants – three quarters of them women, with an average age of 53 – for five years.

The participants, aged between 36 and 62, already owned a Fitbit device that measures steps and were without obesity – at the start of the trial – walking an average of 8,326 steps a day.

The researchers found that those in the top quarter of society for genetic obesity risk would need to walk 26 per cent further a day than those with an average risk.

That meant that those at highest genetic risk needed to walk 11,020 steps a day to have an even chance of becoming obese over five years – 2,280 more than those with an average risk of obesity, who needed to take 8,740 steps for the same result.

But someone in the bottom quarter of genetic risk would have the same 50/50 chance of obesity if they walked just 5,080 steps a day – 54 per cent fewer than those in the top quarter for risk and 3,660 fewer steps (40 per cent less) than the average person.

“What is new and important from this study is that we were able to put a number on the amount of activity needed to reduce the risk of obesity,” said lead author Evan Brittain.