PARIS (AFP) - Scientists revealed a "thrifty" gene variant Monday (July 25) that likely helped Samoans store fat and survive in bygone lean times, but has made them among the portliest people in times of plenty.
The variant in the gene CREBRF was common among Samoans - it was present in 45 per cent of some 5,000 participants in a study, a research team reported in the journal Nature Genetics.
"Those with it were likely to have a higher BMI than those who didn't have it," they wrote - referring to the international measure of "body mass index" - a ratio of weight-to-height squared.
Having the variant was associated with 35 per cent higher odds of being obese, said a statement from Brown University in the United States, which was involved in the study.
The variant is virtually non-existent in Africans, Europeans or their descendents, and is "very, very rare" in East Asians.
According to the study authors, 80 per cent of Samoan men and 91 per cent of Samoan women were overweight or obese in 2010.
And while genetics cannot bear all the blame, it does complicate matters.
"We believe that this variant became so much more common in Samoans because it was historically advantageous to them as a population," study author Stephen McGarvey of the Brown University School of Public Health told AFP.
A gene that makes the body "thrifty" by storing fat and energy would have been useful in the face of food scarcity when early Samoans first settled the South Pacific islands.
This would have led to natural selection favouring those carrying the gene variant, and it becoming more prominent.
But today's reality of high-calory diets and limited exercise "may place people with this variant at an additional disadvantage in terms of being overweight and obese," he said.
On the other hand, it did seem to offer protection against type 2, so-called adult-onset, diabetes, which is linked to overweight.
"Samoans weren't obese 200 years ago," said McGarvey.
"The gene hasn't changed that rapidly - it's the nutritional environment that changed that rapidly."
But this did not mean obesity was inevitable.
"Don't take this as 'You are Samoan, you are fated to be obese,'" he said.
"We don't think that's true. We don't have any evidence that that's the case. A healthy diet and physical activity are still key to maintaining a healthy weight."