A low-carb, high-fat diet is a more effective way to lose weight than calorie counting, scientists claim.
A study led by researchers at Harvard suggests cutting carbohydrate-rich foods such as pasta, bread and sugar helps keep the kilos off in the long-term.
And the scientists found that a low-carb diet actually helped the body burn off more energy.
Most dieters who rely on calorie counting alone put the weight back on within a year or two. This is because the body adapts by slowing the metabolism and burning fewer calories, leading to yo-yo dieting.
But the experts found that those who focused on cutting carbs saw their metabolism increase, burning more calories and reducing weight.
The scientists, writing in the British Medical Journal, said this effect would lead to an extra 20lb (9kg) weight loss over three years, even if someone did not change their overall calorie intake at all.
The key, they said, is to limit the ‘glycaemic load’ on the body – a measure of how much a food will cause blood sugar to rise. Carbohydrates are broken down by the body into sugar, giving them a higher glycaemic load than fat.
‘A low glycaemic-load, high-fat diet might facilitate weight loss maintenance beyond the conventional focus on restricting energy intake and encouraging physical activity,’ they wrote. The experts tracked 234 overweight adults who were put on an initial weight-loss diet for about ten weeks.
They were then split into groups to follow high, moderate or low-carbohydrate diets – with carbs comprising 60, 40 or 20 per cent of total calories – for an additional 20 weeks.
In all three groups, calorie intake was adjusted so participants’ weight did not change notably. The goal was to compare energy expenditure, to see how the groups burned calories at the same weight.
The scientists found that total energy expenditure was significantly greater on the low-carb diet versus high-carb.
At the same average body weight, participants on the low-carb diet burned about 250 calories a day more than those on the high-carb diet.
The findings are the latest in the decades-old row over the merits of low-fat diets versus low-carb diets.
British health officials advise a daily diet based on ‘starchy carbohydrates’, with a limited intake of saturated fat – in contrast to this study.
Researcher Dr David Ludwig said: ‘Processed carbohydrates that flooded our diets during the low-fat era have raised insulin levels, driving fat cells to store excessive calories.
‘With fewer calories available to the rest of the body, hunger increases and metabolism slows – a recipe for weight gain.’
But Professor Tom Sanders, of King’s College London, warned the low-carb diet contained ‘a horrendous amount of saturated fat’ which would ‘increase blood cholesterol levels and risk of heart disease’.