By John Kerr 26/07/2016


High rates of obesity in Samoa have been linked to a particular version of a gene which is prevalent among the island’s population. However, relying on the often repeated formula of ‘gene X’ causes ‘condition Y’ risks oversimplification, say experts.

The results, published today in Nature Genetics, were based on an analysis of DNA samples and basic health data collected from over 5,000 Samoan volunteers. The researchers found that individuals carrying a particular version of a gene called CREBRF had about 35 percent higher odds of being obese compared to not having the gene variant.

While this elevated risk is much greater than any other common known genetic link to body-mass index, overall it explains only about 2 percent of the variation in weight among Samoans. Other factors such as diet, physical activity and early life nutrition and growth are important, and their influences on obesity in the context of this gene variant will be investigated in future studies, say the authors.

The CREBRF variant is common in Samoans (present in about 45 percent of the population) but is extremely rare in other populations, most likely as a consequence of Samoa’s small founding population and relatively isolated existence over the last 3,000 years.

Genes only part of the picture in Samoa

Stephen McGarvey, corresponding author of the Nature Genetics study and professor in the Brown University School of Public Health cautioned against interpreting the discovery to mean that obesity is inevitable for Samoans. “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.”

“Samoans weren’t obese 200 years ago,” he said. “The gene hasn’t changed that rapidly – it’s the nutritional environment that changed that rapidly.”

You can read more about the study on Scimex.org.

A market in West Samoa
A market in West Samoa. Credit: Flickr / Sarah Kelemen Garber.

Genes, ethnicity and health: tread lightly

While the results have been welcomed as a new insight into the links between genetics and obesity, independent experts also caution against over-interpreting the results in a social context.

Dr Mike King, a Bioethics lecturer at Otago University commented to the Science Media Centre:

“Obesity is a phenotype that is generally socially disfavoured, and this research risks creating or strengthening in the minds of others an association between Samoan people and obesity, and therefore promoting or supporting social disfavour and harmful discrimination.

“The role of environmental factors not only on the claimed function of this gene variant, but also on the occurrence of obesity should always be explained in research of this type. These environmental factors can be cultural, social, economic, and political. They are extremely important, and often influenced by the views and actions of the population in question, and others.”

In New Zealand, scientists have come to understand the importance of accurately reporting genetics results the hard way. In 2006 a now infamous study by New Zealand scientists reported a link between a particular gene variant involved in neurotransmitter metabolism and aggression in Māori males. The study, based on a small sample, caused an uproar at the time, with many researchers decrying the potentially racist undertones of the research and how it was reported.

In the decade since, there has been progress in New Zealand in developing ethical frameworks that acknowledge the potential for results from gene association studies, especially those focusing on minority groups, to spill over in the social and political realms with unplanned consequences.

The need for nuance in describing and reporting results of genetics research drawing from particular ethnic groups was not lost on Dr Ofa Dewes, a Pacific Health researcher at the University of Auckland and the Maurice Wilkins Centre. Commenting to the Science Media Centre on the new research, she said:

“Further studies to better understand the genetic variants and causes of obesity among ethnic-specific Pacific populations, and community engagement to raise awareness, advocacy and knowledge-transfer to other population groups in New Zealand and in the Pacific region at risk of obesity and/or non-communicable diseases, will be required.

“Meanwhile, this scientific discovery and its implications will need to be clearly explained to Pacific communities and stakeholders as a priority, and the New Zealand public as a whole.”