Obesity-associated FTO gene does not affect outcome after weight loss intervention

A worldwide review of randomised controlled trials, looking at the effect of the fat mass and obesity associated FTO gene on weight loss, has found that people carrying it respond as well as the rest of the population to weight loss treatments.
In 2007, the FTO genotype was identified in genome-wide association studies (GWAS) as a heritable risk factor for obesity. A correlation between different FTO variants and risk of type 2 diabetes was also detected.
Research then shown strong associations between certain variations of the FTO gene in the fat mass and body mass index (BMI) in multiple populations, with the gene’s main effect thought to be on controlling feeding behaviour and energy expenditure.
According to the authors of the current study, people who carry two copies of the gene weigh about 3 kg more and have 1.7 times increased odds of becoming obese, compared with those who have only one copy of the gene.
The research, published online in the BMJ, analysed data from over 9500 overweight or obese (with a mean BMI of 32.2) participants involved in eight different trials conducting dietary, physical activity, or drug-based interventions.
It compared the changes seen in BMI, body weight, or waist circumference by obesity susceptibility FTO variants following these interventions.
At the start, individuals who carried one copy of the gene had significantly increased BMI, body weight, and waistline circumference.
However, the researchers found that the (minor allele) FTO genotype had no detectable effect on weight loss in response to intervention. The changes did not differ by intervention type or length either and were independent of the participants’ ethnicity, gender, age, and baseline BMI.
For Katherine Livingstone from Newcastle University, and one of the authors of the review, the findings suggest that the genetic predisposition to obesity associated with the FTO minor allele can be at least partly counteracted through the interventions (dietary, physical activity, or drug-based).
While the findings are promising, weight loss interventions based on an individual’s genes may not be the answer for the larger population.
The management of obesity through long-term improvements in lifestyle behaviours, principally eating patterns and physical activity, will be of greater benefit to the population and will be effective irrespective of FTO genotype.