People with 'obesity gene' can still lose weight

"No excuses not to slim as 'fat gene' found not to affect ability to lose weight," reports The Daily Telegraph.

It is one of several news outlets to report on research suggesting people who put on weight easily because of a genetic variant do just as well as other people on weight loss interventions such as diet, exercise and drug-based treatments.

A variant of the FTO gene is one of 97 potential gene variants thought to influence people's chances of being overweight or obese. The FTO variant has been shown to have the strongest association with obesity. People with two copies of the variant weigh on average 3kg more and are 1.7 times more likely to be obese.

The study included 9,563 people from eight separate studies of weight loss programmes involving various combinations of diet, exercise, medication and behaviour change treatment.

Researchers looked at how people with an obesity-promoting variant of the FTO gene fared, either on treatment or in control groups, compared to those without the gene variant. They also looked to see whether people with the gene variant responded better to one type of weight loss treatment than another.

They concluded that, while FTO variant genes make it more likely that people will be overweight, it doesn't affect their ability to lose weight through diet and exercise or other treatment. In addition, no one treatment or intervention worked better for them than any other.

The researchers also suggest there would be little point in screening overweight people for the FTO gene variant, as this would not predict the success of their treatment programmes.

Where did the story come from?

The study was carried out by researchers from 25 different international institutions, led by Newcastle University in the UK, and was funded by the Alfred Deakin postdoctoral research fellowship and the UK Medical Research Council.

The study was published in the peer-reviewed British Medical Journal (BMJ) on an open-access basis meaning it is free to read online.

While The Guardian gave a good overview of the science behind the study, the Mail Online confused the ability to lose weight with the chances of gaining weight and its headline seemed to take pleasure in pointing a finger at obese people: "It's not in the genes! You can't blame your DNA for piling on the pounds".

Although the Mail's story later made clear the FTO gene variant does in fact increase the chances of "piling on the pounds", the tone is set by the headline.

The Telegraph decided the research showed there were "No excuses not to slim" and that carriers of the gene variant will be "bang out of excuses" for their weight.

What kind of research was this?

This was a systematic review and meta-analysis of randomised controlled trials. This type of study is sometimes called the "gold standard" for research, because it pools data from the best quality studies that compare how people respond to different types of treatment. However, it is reliant on the quality of the underlying studies.

What did the research involve?

Researchers looked for all randomised controlled studies of weight loss treatments carried out in overweight or obese adults, which had information about people's FTO genotype. They asked the study authors to provide data on the individual patients, not just the summarised published data. They then pooled the data from the studies, and ran a number of tests for potential bias or confounding factors.

They calculated whether there was a difference in the measures of weight of people with and without the FTO variant; whether treatment response varied by FTO variant, and whether this was affected by factors including age, sex, initial weight and ethnic background.

They included studies with measures of body mass index (BMI), waist circumference and body weight. They excluded three studies which they'd wanted to include, but where they could not get individual patient data. They searched only for studies published with an English language abstract, which means some foreign language studies might have been missed.

What were the basic results?

The researchers found no significant differences between weight loss outcomes in people with and without the FTP variant, regardless of the type of weight loss treatment used. This applied to all measures of weight loss – waist circumference, BMI and body weight – and to all lengths of treatment and study follow up (from eight weeks to three years).

How did the researchers interpret the results?

The researchers said their results showed that "people who carry obesity risk FTO genotypes respond equally well to weight loss treatment."

They say their findings show the genetic predisposition to obesity associated with the FTO variant "can be at least partly counteracted through dietary, exercise, or drug-based weight loss interventions."

Conclusion

There's been a lot of interest in how our genes interact with our environment and lifestyle when it comes to body weight.

The discovery that certain gene variants are associated with a higher chance of becoming overweight or obese has been taken by some to mean that people's weight is genetically determined. That could lead to people fearing there's no point in them trying to lose weight, but this study shows that isn't the case.

The results sound like good news for anyone who wants to lose weight for health reasons. Diet and exercise programmes can help, and even if you carry the "obesity gene" variant, these results suggest you have as much chance of success as anyone else.

This is particularly important for the increasing numbers of adults who are overweight or obese. According to the 2014 Health Survey for England, 62% of adults were either overweight or obese and 23% were obese.

There are a few points to bear in mind:

• the summary included only eight studies, with a relatively low number of participants overall for a meta-analysis
• the study only looked at one type of genetic variant, although this was the one most strongly linked to obesity. It's possible that other genetic variants or combinations do have an effect on weight loss
• the majority of the studies were carried out in white people from Europe or the US, so we don't have a clear picture from this study whether ethnic background affects outcomes differently
• due to the short follow up of some studies, we can't tell whether the genetic variant might affect the chances of putting weight back on after initial weight loss

For information about how to reach and maintain a healthy weight with diet and exercise, see our 12 week weight loss guide.