Why some people who live on junk food are thin

Slim people are lean as the result of genetic advantage and not always because they are more disciplined when it comes to portion control, a study has suggested. New research from Cambridge University indicates that the genetic cards are stacked in favour of slim people and against those considered obese.

“We have far less control over our weight than we might wish to think.” DNA from 1,622 thin volunteers from the cohort, called the Study Into Lean and Thin Subjects (STILTS), was compared with that of 1,985 severely obese people and a further 10,433 normal weight controls.

Researchers acknowledged that factors such as easy access to high calorie foods and sedentary lifestyles can impact on a person’s weight, but said there is considerable individual variation within a population that shares the same environment. “We already know that people can be thin for different reasons,” said professor Farooqi after the study was published in the journal PLOS Genetics.

“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,” said professor Sadaf Farooqi of Cambridge’s Wellcome-MRC Institute of Metabolic Science who led the study. While it may be easy to judge and criticise an individual for their weight, “the science shows that things are far more complex,” he added.

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. The study’s authors said it may allow them to pinpoint new genes and biological mechanisms that help people to stay thin.

More than 6 in 10 (59-65%) adults in the UK are overweight, while one in four adults and one in five children aged 10-11 is obese, according to the NHS. The researchers acknowledged that external factors, such as easy access to high calorie foods and sedentary lifestyles, can influence a person’s weight. However, they say there is substantial individual variation within a population that shares the same environment. “We already know that people can be thin for different reasons,” said Prof Farooqi.

“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 them from putting on weight, we may be able to target those genes to find new weight loss strategies and help people who do not have this advantage.”