medwireNews: Overweight and obese people who carry two minor alleles of the fat mass and obesity associated gene (FTO) respond just as well to weight loss interventions as noncarriers, shows a meta-analysis of individual participant data.
John Mathers (Newcastle University, UK) and study co-authors assessed data from 9563 participants in eight randomised controlled trials of weight loss interventions and found that carriers of the minor allele lost, by and large, no more or less weight than noncarriers.
For example, although each copy of the minor allele was associated with a very slightly larger reduction in body mass index, with a regression coefficient of –0.02, this was not statistically significant, with the 95% confidence interval ranging from –0.13 to 0.09.
The same was true of the other major outcomes of bodyweight and waist circumference, reports the team, and occurred despite a clear baseline effect of the FTO minor allele. Each copy of the minor allele was associated with a 0.31 kg/m2 higher baseline body mass index, a 0.89 kg increase in weight and a 0.63 cm increase in waist circumference.
Alison Tedstone, chief nutritionist from Public Health England, London, writes in a linked editorial that, even using the previously quoted 3 kg excess weight gain associated with the FTO gene, when gained over 20 years, this only amounts to the consumption of around 500 excess kcal per year.
By contrast, she says that people in England currently consume an average 200–300 kcal/day more than they need. “It is therefore hard to see the over-consumption driven by the FTO gene as a serious problem for public health”, she writes in The BMJ.
The weight differences attributed to the FTO gene “are minor compared with the degree of excess weight gain seen across populations”, Tedstone stresses.
She writes: “If we are to turn back the tide of obesity, an understanding of how diet and lifestyle interact with the genome might help some people, particularly those with rare conditions that cause devastating levels of weight gain in early life.
“It is increasingly evident, however, that the idea that personalised interventions based on the genome will yield population benefit, may not pay off, at least in the short term.”
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