British scientists have discovered that people with fewer copies of the AMY1 “carb breakdown” gene are more likely to become obese.
They put on weight when they eat foods like bread and potatoes because they have fewer AMY1 genes and make less of an enzyme called Amylase, which helps digest carbohydrates.
Researchers at King’s College London and Imperial College London said it showed a “one size fits all” diet is pointless.
Prof Tim Spector, of King’s College, said six million people may have too few copies of AMY1.
He said: “A calorie for one person is not the same for another person. In the future a simple blood or saliva test might be used to measure enzymes like amylase and therefore shape dietary advice.”
Published in Nature Genetics, the study found AMY1 was consistently linked to obesity after examining the DNA of nearly 5,000 people.