Gene helps explain high levels of obesity in Samoa: study

Transcript

American researchers have discovered close to half of all Samoans have a gene that increases their risk of becoming obese.

It's thought the gene is likely to be an adaptation to their ancestors' migrations across the Pacific, with survivors most likely to be those with the gene.

Karen Brown reports.

The US study identified a gene researchers say gives those who have it a 35 percent higher chance than others of being obese.  They say it helps explain why 80 percent of Samoan men and 91 percent of Samoan women were overweight or obese in 2010.  But they also say it explains just two percent of weight differences overall, with the usual factors of diet, physical activity and early life nutrition and growth responsible for the remainder.  And, perversely, those with the gene were less likely to have type two diabetes.  Auckland University professor Peter Shepherd says the gene acts like a master switch for other genes.

PETER SHEPHERD: "What it does is it stores a little bit of extra fat into fat tissue every time the people who have the gene eat food so in times gone by that ability to store an extra bit of fat would've been a really good protection against times of starvation and the way the gene has been inherited suggests that that's the reason it's accumulated in certain people."

Professor Shepherd says the gene protects against type two diabetes because fat is stored in cells where it can't cause harm rather than in organs.  He says more research is needed, but the findings are valuable.

PETER SHEPHERD: "This is the first study to find any gene linked to obesity and diabetes in the Samoan population so it's a really important finding because it gives us for the first time a starting point from which we can develop targeted intervention strategies."

An Otago University geneticist, Tony Merriman, says 45 percent of Samoans have the gene, but elsewhere it's rare.

TONY MERRIMAN: "So it's telling us that there's something unique about weight control and obesity in Samoans, and this may be translatable to people, Samoan people, Tongan, Pacific and Maori living in New Zealand."

Professor Merriman says studies are already under way here, at the Maurice Wilkins Centre, to see if it's present in Maori and Pacific people.

TONY MERRIMAN: "We will look at this genetic variant with a study that we're doing with the Maurice Wilkins Centre in New Zealand in Maori and Pacific people to see if it's having the same effect in New Zealand. We can't assume it is, we need to do that study in New Zealand as well."

The US researchers stress Samoan people should not believe they're fated to be obese and that it's the environment not them that's changed.  An Auckland doctor, Robyn Toomath, who founded the Fight The Obesity Epidemic, agrees.

ROBYN TOOMATH: "The people who are genetically susceptible are very very sensitive to an adverse physical environment so this is why obesity rates are so much higher when the genetic susceptibilities haven't changed for centuries."

An Auckland-based Pacific health researcher, Ofa Dewes, says Samoans want more information about obesity.

OFA DEWES: "They are saying, well I'm doing more of this and I have family, but why are only some of us prone to overweight or obesity, or even type 2 diabetes and others are not?"

Researchers here and in the US say answers are coming, it's just taking time.

The findings have been published in the journal, Nature Genetics.