In the largest study of its kind to date, Sadaf Farooqi’s team looked at how some people manage to stay thin while others gain weight. With support from Wellcome and the European Research Council, the team recruited 2,000 people who were thin (body mass index (BMI) of less than 18 kg/m2) but healthy into the Study Into Lean and Thin Subjects – STILTS. In a paper published in PLOS Genetics, and working with Dr Inês Barroso’s team at the Wellcome Sanger Institute, the team examined genetic variants in 1,622 thin volunteers from the STILTS cohort, 1,985 severely obese people and 10,433 normal weight people. The team 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 researchers added up the contribution of the different genetic variants to calculate a risk score. Obese people had a higher genetic risk score than normal weight people, whereas thin people, had a much lower genetic risk score – they had fewer genetic variants that we know can 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,” says Professor Farooqi. “It’s easy to rush to judgement and criticise people for their weight, but the science shows that things are far more complex. We have far less control over our weight than we might wish to think.”
Three out of four people (74%) in the STILTS cohort had a family history of being thin and healthy and the team found some genetic changes that were significantly more common in thin people. This research may allow them to pinpoint new genes and biological mechanisms that help people stay thin and ultimately target those mechanisms for new weight loss strategies.