April 17, 2007
FTO Gene Ups Odds Of Obesity

Why let your spouse blame your diet for your unwanted fat when you can blame your genes instead?

Scientists have identified the most clear genetic link yet to obesity in the general population as part of a major study of diseases funded by the Wellcome Trust, the UK's largest medical research charity. People with two copies of a particular gene variant have a 70 per cent higher risk of being obese than those with no copies.

We can probably expect discovery of more genetic variations that contribute to obesity. They all serve as clues for how the brain and body regulate weight. All these clues will lead to the development of drugs and other treatments that make obesity rare in developed countries. 20 years from now I expect obesity to be rare.

A variation of the gene FTO makes a big weight difference.

Scientists from the Peninsula Medical School, Exeter, and the University of Oxford first identified a genetic link to obesity through a genome-wide study of 2000 people with type 2 diabetes and 3000 controls. This study was part of the Wellcome Trust Case Control Consortium, one of the biggest projects ever undertaken to identify the genetic variations that may predispose people to or protect them from major diseases. Through this genome-wide study, the researchers identified a strong association between an increase in BMI and a variation, or 'allele', of the gene FTO. Their findings are published online today in the journal 'Science'.

The researchers then tested a further 37 000 samples for this gene from Bristol, Dundee and Exeter as well as a number of other regions in the UK and Finland.

Carrying 2 copies of the FTO allele brings with it about 3 kg or 6.6 lb more weight.

The study found that people carrying one copy of the FTO allele have a 30 per cent increased risk of being obese compared to a person with no copies. However, a person carrying two copies of the allele has a 70 per cent increased risk of being obese, being on average 3 kg heavier than a similar person with no copies. Among white Europeans, approximately one in six people carries both copies of the allele.

The existence of genetic variations that cause weight gain is not surprising. Calorie malnutrition was probably the biggest cause of death for most of human history. So genetic variations that cause weight gain during good times would have conferred survival advantages. But why don't all people have the same strongest tendency to weight gain? To put it another way: what diadvantages of this FTO allele prevented it from becoming the only version of the FTO gene in humans?

A continued decline in the cost of DNA testing will accelerate the rate of discovery of important genetic variations. In the next decade we are going to find out in enormous detail most of the genetic variations that control many aspects of who we are.

Share |      Randall Parker, 2007 April 17 10:29 PM  Brain Appetite


Comments
Kurt9 said at April 18, 2007 10:17 AM:

The theory that humans, particularly caucasians, have a genetic propensity to gain weight as a genetic adaptation to the threat of famine is well-known to all.

This theory fails to account for the fact that the East Asians (Japanese, Korean, and Chinese) do not have this propensity to get fat easily even though it is well known that the East Asian populations have other genetic adaptations to cold weather.

Eric said at April 21, 2007 10:31 PM:

So what exactly does this gene do? Does it cause decreased insulin sensitivity? Does it reduce leptin signalling? Does it alter the receptors on adipocytes? Does it reduce satiety signaling?

I think it's essentially worthless to know there is an obesity gene if you don't know what it does. When they figure out how it works, let me know.

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