Clinical Question

What is the effect of a Mediterranean-type diet on body weight?

Bottom Line

In addition to improving cardiovascular outlook, a Mediterranean diet produced greater sustained weight loss than a low-fat diet and similar weight loss to other diets in patients who were overweight or obese, most of whom had type 2 diabetes mellitus. The range of average weight loss was 3.8 to 10.1 kg (8.4 to 22.3 lb) after one year with a Mediterranean diet vs. a loss of 5.0 kg (11.0 lb) to a gain of 2.9 kg (6.4 lb) with a low-fat diet. (Level of Evidence = 1a−)

Synopsis

The so-called Mediterranean diet consists of high consumption of fruits and vegetables; monounsaturated fats, usually from olive oil; moderate consumption of poultry, fish, and dairy; and little or no red meat. To identify studies for this meta-analysis, the authors searched three databases, including the Cochrane Library, and identified five studies (N = 998) of at least 12 months' duration that investigated the diet's effect on weight loss. The authors also searched reference lists of identified studies, reviews, and other meta-analyses. The included studies were published in English or French. Several of the studies had high dropout rates but were otherwise at low risk of bias. Study results were heterogeneous, and therefore the authors were unable to combine the results. The patients in the studies were between 44 and 67 years of age and were obese or borderline obese, with an average body mass index (BMI) of 29.7 to 33.5 kg per m². Most of the patients in the studies had type 2 diabetes. After 12 months, the Mediterranean diet produced moderate weight loss, an average range of 3.8 to 10.1 kg across the studies, with an average BMI change of −1.0 to −3.33 kg per m². These averages were greater than those found with a low-fat diet but similar to a low-carbohydrate diet and an American Diabetes Association diet with similar proportions of protein, fat, and carbohydrates.

Study design: Systematic review

Funding source: Self-funded or unfunded

Setting: Various (meta-analysis)

Reference: ManciniJGFilionKBAtallahREisenbergMJSystematic review of the Mediterranean diet for long-term weight loss. Am J Med2016;129(4):407–415.