People who carry a variant in the so-called obesity gene, FTO, react just as well to diet and exercise as those without it, a research paper said Wednesday.
This means that people with the variant, which appears to be linked to a higher risk for being overweight, are not necessarily doomed to remain so, according to a meta-analysis published in The BMJ medical journal.
"Individuals carrying the (variant) respond equally well to dietary, physical activity, or drug based weight loss interventions," wrote the authors of the review of eight studies involving some 10,000 people.
This meant that genetic predisposition to obesity "can be at least partly counteracted through such interventions."
Scientists have previously shown an association between a variant of the FTO gene and surplus body fat, but little is understood about how the link works.
The relative contribution of genetics and lifestyle to the global obesity epidemic is still very much in dispute.
The latest review showed that participants in weight loss programmes who had the FTO variant started out almost a kilo (about two pounds) heavier on average than those without it.
But changes in weight were similar in people with the variant and those without it, regardless of other factors such as ethnicity or gender, the authors said.
In 2014, according to the World Health Organization, more than 1.9 billion adults globally were overweight. Of those, more than 600 million were obese.
Carrying excess weight has been linked to heart disease, stroke and certain cancers.
Commenting on the latest research, Public Health England agency chief nutritionist Alison Tedstone said the causes of the obesity epidemic may have little to do with genes.
The study, she said, "adds to the evidence suggesting that environmental factors might dominate over at least common obesity linked genes".
Such factors could include a high-sugar diet or insufficient physical exercise.
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Katherine M Livingstone et al. FTO genotype and weight loss: systematic review and meta-analysis of 9563 individual participant data from eight randomised controlled trials, BMJ (2016). dx.doi.org/10.1136/bmj.i4707