Slim people should thank genes not 'moral superiority' for weight, study suggests

‘We have far less control over our weight than we might wish to think’

It may be easy to judge and criticise an individual for their weight but “the science shows that things are far more complex' (Getty Images)

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.

“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. “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 Prof Farooqi after the study was published in the journal PLOS Genetics. "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."

Three out of four people (74 per cent) 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 per cent) 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.”

Dr Ines Barroso of the Wellcome Sanger Institute, which collaborated on the study, adds: “As anticipated, we found that obese people had a higher genetic risk score than normal weight people, which contributes to their risk of being overweight. The genetic dice are loaded against them.”