An overseas study could have unlocked the secret as to why Samoans have some of the world's highest obesity levels.

The Brown University study found a gene variant increases the risk of obesity, but decreases the risk of Type 2 diabetes.

Auckland University professor, Peter Shepherd, said it's a fascinating starting point.

"The initial clues seem to suggest that this helps store fat tissue, and surprisingly this protects these people against getting Type 2 diabetes."

Professor Shepherd said there's a growing realisation that metabolism can be controlled in many different ways in different people.

"Now, this sort of genetic information tells us that that really is the case, so we're going to need individualised strategies to help really in the control of weight and metabolic diseases."