LONDON - Exercise plays a much lesser role in weight loss than healthy eating, say doctors.

Cutting out excess sugar and carbohydrates is the key.

In an editorial in the British Journal Of Sports Medicine, three international experts said it was time to "bust the myth" about exercise, a BBC report said. While physical activity was a key part of staving off diseases such as diabetes, heart disease and dementia, its impact on obesity was minimal.

The experts blamed the food industry for encouraging the belief that exercise could counteract the impact of unhealthy eating. They described its tactics as "chillingly similar" to those of Big Tobacco on smoking, BBC said.

The experts, who included London cardiologist Aseem Malhotra, pointed to evidence that up to 40 per cent of people whose weight was in the normal range would still have harmful metabolic abnormalities typically associated with obesity.

And yet, public health messaging had "unhelpfully" focused on calorie-counting to maintain a healthy weight when it was the source of calories that mattered most, they said.

Research has shown that diabetes increases 11-fold for every 150 additional sugar calories consumed compared to fat calories.

And they pointed to evidence from The Lancet medical journal's global burden of disease study, which showed that unhealthy eating was linked to more ill health than lack of exercise, alcohol and smoking combined.

Dr Malhotra said: "An obese person does not need to do one iota of exercise to lose weight. He just needs to eat less.

"My biggest concern is that the messaging that is coming to the public suggests you can eat what you like as long as you exercise. That is unscientific and wrong. You cannot outrun a bad diet."

Still, others said it was risky to play down the role of exercise. Professor Mark Baker of the National Institute for Health and Care Excellence, which recommends "well-balanced diets combined with physical activity", said it would be "idiotic" to rule out the importance of exercise.

A Food and Drink Federation spokesman was quoted by the BBC as saying that the benefits of physical activity were not food industry hype or conspiracy, and a healthy lifestyle would include both a balanced diet and exercise.