We recently discovered why some people manage to stay thin while others gain weight.
To find out why and how some people find it easier to stay thin than others, we established the Study Into Lean and Thin Subjects – STILTS. We recruited 2,000 people who were thin (defined as a body mass index (BMI) of less than 18 kg/m2) but healthy, with no medical conditions or eating disorders. With Dr Inês Barroso’s team at the Wellcome Sanger Institute we compared the DNA of 1,622 thin volunteers from the STILTS cohort, 1,985 severely obese people and 10,433 normal weight people. We found new genetic regions involved in severe obesity and some involved in healthy thinness.
When we added up the contribution of different genetic variants to calculate a genetic risk score, we found that obese people had a higher score than normal weight people, which contributes to their risk of being overweight. Importantly, we also showed that thin people, had a much lower genetic risk score – they had fewer genetic variants that we know increase a person’s chances of being overweight.
This research shows for the first time that healthy thin people are generally thin because they have a lower burden of genes that increase a person’s chances of being overweight and not because they are morally superior, as some people like to suggest.
We already know that people can be thin for different reasons. Some people 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 those people from putting on weight, we may be able to target those genes to find new weight loss strategies.