Scientists have discovered an obesity gene which may partly explain why Samoans have some of the highest obesity rates in the world.
But just how much can it be to blame for being overweight?
The gene seems to originate from the days when Samoans took long ocean voyages, so their bodies became great at storing fat.
It's known as a 'thrifty gene' - and some scientists think Aboriginals in Australia may also have something similar.
But while figures show 80 percent of Samoan men and 91 percent of women are classified as overweight, only 45 percent of Samoans actually carry the obesity gene.
The gene gives you a 35 percent higher chance of being overweight - but scientists say factors like diet and exercise are still important.
Similar patterns are found in Mexico, where those who carry an obesity gene are on average 5cm bigger around the waist than those who don't - but Mexico is also the world's leading consumer of Coca-Cola per capita.
Several other obesity genes have been documented in the past, but they each have only a small effect on weight.
A 2015 University of Michigan study found 97 different regions of the human genome were associated with increased BMI.
The most well-known of these genes - called FTO - is associated with a modest 0.4 increase in BMI, and affects a large number of people.
Then there's a study which shows chubby Labradors may be genetically predisposed to obesity.
But new, and obvious, research shows that moderate exercise - even as little as one or two hours per week - can substantially weaken an obesity gene's influence.