In the largest study of its kind to date, researchers have looked at why a few people manage to stay thin while others gain weight easily. They have discovered that the hereditary dice are loaded in favour of thin people and against those at the obese end of the spectrum.
More than six in ten adults are overweight, and one in four adults is obese. By age five, almost one in four children is either obese or overweight. Excess weight increases the risk of related health problems including heart disease and type 2 diabetes.
While it is well known that changes in our environment, for example, easy access to high calorie foods and sedentary lifestyles, have driven the rise in obesity in recent years, there is considerable individual variation in weight inside a populace that shares the same environment. A few people seem able to eat what they like and remain thin. This has led a few people to characterise overweight people as lazy or lacking willpower.
The researchers examine why and how some people find it easier to stay thin than others. Studies of twins have demonstrated that variation in body weight is generally affected by our genes. To date studies have overwhelmingly focused on people who are overweight. Hundreds of genes have been discovered that increase the possibility of an individual being overweight and in some people faulty genes can cause severe obesity from a young age.
Our DNA contains of a sequence of molecules known as base pairs, represented by the letters A, C, G and T. Strings of these base pairs form genetic regions. Our genes provide the code for how our body functions and changes in the spelling.
The team found a few regular genetic variants already identified as playing a role in obesity. Moreover, they found new genetic regions involved in severe obesity and some involved in healthy thinness.
To see what impact these genes had on an individual’s weight, the specialists included the contribution of the different genetic variants to calculate a genetic risk score. As anticipated, we found that obese people had a higher genetic risk score than normal weight individuals, which contributes to their risk of being overweight. The genetic dice are loaded against them.
Importantly, the team also showed that thin individuals, had a much lower hereditary risk score they had less genetic variants that we know increased an individual’s chances of being overweight.
This examination shows for the first time that healthy individuals are commonly thin because they have a lower burden of genes that increase an individual’s chances of being overweight and not because they are morally superior, as certain individuals like to suggest. It’s easy to rush to judgement and criticise individuals for their weight, but the science shows that things are far more complex. We have far less power over our weight than we may wish to think.
We already know that individuals can be thin for various reasons. A few individuals are just not that interested in food whereas others can eat what they like, but never put on weight. If we can find the genes that prevent them from putting on weight, we might most likely focus on those genes to discover new weight loss strategies and help individuals who do not have this advantage.