Workers who were put on a Mediterranean diet for two years tended to regain less weight over the years afterward than volunteers placed on a low-fat or low-carbohydrate diet, new data show.
They also had the biggest long-term drop in cholesterol - although the differences between groups weren't always clear-cut.
The findings, reported online in The New England Journal of Medicine, suggest dietary programmes promoted in the workplace can have long-lasting benefits, especially among people on Mediterranean and low-carb diets, researchers said.
One of the traditional limitations with weight-loss programmes is that once the intervention ends, dieters regain the weight.
How the study was done
So for the new study, researchers assigned 322 moderately-obese people to one of the three diets for two years, and then continued following them for four more years.
The participants had an average body mass index of 31, and most were men.
Lead researcher Dr Dan Schwarzfuchs of the Nuclear Research Center Negev in Dimona, Israel reported that after two years on the diets, average weight loss was 2.9 kg (6.4 lb) in the low-fat diet group, 4.4 kg (9.7 lb) in the Mediterranean diet group, and 4.7 kg (10.3 lb) in the low-carb dieters.
Four years later, data from 259 of the original participants showed 67% had stayed with their original diet, 11% had switched to another diet and 22% had stopped dieting.
And although people in the low-fat and low-carb groups had regained almost all the weight they'd originally lost, volunteers assigned to the Mediterranean diet only regained 3.1 pounds during the four-year follow-up, on average.
People in the study didn't know they were going to be tracked after the original study ended, Dr Schwarzfuchs said. "They were free to do what they wanted. We wanted to see what goes on in real life."
What the study found
He said the findings were not particularly surprising. "The restricted-calorie low-fat diet is difficult for people to stick to. With the Mediterranean diet, you can eat almost everything," he said. "It's more compatible with life."
The team also found that the Mediterranean diet produced the best long-term reduction in total cholesterol, with an average drop of 13.9 mg/dL after six years. However, the low-carbohydrate diet group had the biggest reduction in the ratio of LDL to HDL cholesterol.
Dr Meghana Gadgil of the Johns Hopkins University School of Medicine in Baltimore said the study "hints that the beneficial changes seen with a high-fibre, high monounsaturated fat diet are sustainable in the longer-term."
But given that one-third of the participants stopped dieting or switched diets, she noted that it's hard to draw conclusions about which diet worked best.
"Those randomised to the Mediterranean diet were able to maintain the highest degree of weight loss, however it is unclear whether it is those who have maintained the Mediterranean diet who are driving those results," said Dr Gadgil, who wasn't involved in the research.
She also said the cholesterol improvements in the low-carb group were "interesting," given that those dieters regained the most weight over the follow-up period.
The study was supported by the Nuclear Research Center Negev, the Chief Scientist Office of the Israeli Ministry of Health, and the Dr Robert C and Veronica Atkins Research Foundation.
(Reuters Health, October 2012)
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