People are defined as overweight if their body mass index or BMI – a ratio of weight to height – is more than 25 kg per metre squared (kg/m2) and obese if it is more than 30 kg/m2. Being overweight or obese increases the risk of many illnesses such as cancer, heart disease and stroke. Together, strokes, heart attacks and other cardiovascular diseases are the biggest killers worldwide and claim more than 17 million lives a year.

Researchers who led the study said its results prove for the first time that people can lose weight without trying to.”The weight reduction..when people ate less fat was remarkably consistent – we saw it in almost every trial. Those who cut down more on fat lost more weight,” said Lee Hooper from the University of East Anglia medical school, who led the work.”The effect isn’t dramatic, like going on a diet,” the research specifically looked at people who were cutting down on fat, but didn’t aim to lose weight – so were continuing to consume a normal amount of food.”What surprised us was that they did lose weight, their BMI (body mass index) decreased and their waists became slimmer,” Hooper said. The lower fat eaters also kept their weight down over at least seven years.