NEW YORK - Sticking to diets with strict proportions of fat, carbs and protein may not be more effective for people who want to lose weight and fat mass than simply cutting back on calories, according to a new comparison of four diets.
The results suggest that it doesn't matter where the calories come from, as long as dieters reduce them.
"If you're happier doing it low fat, or happier doing it low carb, this paper says it's OK to do it either way. They were equally successful," said Christopher Gardner, a Stanford University professor who was not involved in the study.
Dr. George Bray, who worked on the new study, said earlier research had found certain diets -- in particular, those with very little carbohydrate -- work better than others. Diet books also often guide consumers to adopt a particular type of meal plan, such as low-fat or low-carb-high-protein diets.
But there hasn't been a consensus among scientists.
So Bray, of Pennington Biomedical Research Center in Baton Rouge, Louisiana, and his colleagues randomly assigned several hundred overweight or obese people to one of four diets: average protein, low fat and higher carbs; high protein, low fat, and higher carbs; average protein, high fat and lower carbs; or high protein, high fat and lower carbs.
Each of the diets was designed to eliminate 750 calories a day from the people's energy needs.
After six months and again at two years after the diets started, the researchers checked in on people's weight, fat mass and lean mass.
At six months, people had lost more than nine pounds of fat and close to five pounds of lean mass, but some of this was regained by the two-year mark.
People were able to maintain a weight loss of more than eight pounds after two years. Included in that was a nearly three-pound loss of abdominal fat, a reduction of more than seven per cent.
The team found no differences in weight loss or fat reductions between the diets.
"The major predictor for weight loss was 'adherence.' Those participants who adhered better, lost more weight than those who did not," Bray told Reuters Health in an email.
But sticking to a diet is tough, Gardner said. Many of the people who started in Bray's study dropped out, and the diets of those who completed it were not exactly what had been assigned.
For example, the researchers hoped to see two diet groups get 25 per cent of their calories from protein and the other two groups get 15 per cent of their calories from protein. But all four groups ended up getting about 20 per cent of their calories from protein after two years.
"They did have difficulties with adherence, so that really tempers what you can conclude," Gardner told Reuters Health.
Because many people struggle with dieting, Gardner said, they should select the one that's easiest for them to stick with.
Bray recommended a diet developed by some of his co-authors, and which is also endorsed by the National Institutes of Health, called the DASH plan, or Dietary Approaches to Stop Hypertension.
"We would encourage patients to follow this diet modified as they and their Health Care Provider chose to emphasize macronutrient changes that they thought might work best for them," Bray said.
He added that it will be important for future research to determine how best to get people to maintain their diets.
"This area of 'weight loss and weight maintenance' seems to me to be one where fresh insights are most needed," Bray concluded.