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Mediterranean diet and the metabolic syndrome--prevention and reversal without weight changes.

Babio N, Toledo E, Estruch R, Ros E, Martinez-Gonzalea MA, Castaner O et al. 2014. Mediterranean diets and metabolic syndrome status in the PREDIMED randomised trial. CMAJ In Press. DOI:10.1505/cmaj.140764

Increasing the risk of type 2 diabetes and cardiovascular disease, metabolic syndrome is a cluster of 3 or more related cardiometabolic risk factors including central obesity, hypertension, hypertriglyceridaemia, low plasma high-density lipoprotein (HDL) cholesterol levels and hyperglycaemia. Whilst studies have demonstrated lifestyle modifications to be associated with reversion of metabolic syndrome and its components, little information exists on the effect of changes in overall dietary pattern without weight loss in preventing and managing the condition. Using data from the PREDIMED study, which was a large, parallel-group, multicentre, randomised, controlled trial investigating the effect of the Mediterranean diet on primary prevention of cardiovascular disease, study authors evaluated the effect of this diet on the incidence and reversion of metabolic syndrome.

To evaluate the effect of dietary intervention on metabolic syndrome status, the data of participants whom biochemical determinants were available from baseline and at least 2 years of follow up were analysed. Two separate analyses were undertaken: the first on the incidence of metabolic syndrome in participants who did not have the condition at baseline, and secondly, on reversion of metabolic syndrome in participants who had the condition at baseline. Only the first change in status was considered. Participants included men and women (age 55-80) who were at risk of cardiovascular disease and were randomly assigned to one of three dietary interventions: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with nuts, or a control group advised to follow a lowfat diet. Patients were not advised on calorie restriction and physical activity was not promoted for any of the intervention groups.

Of the 7447 participants in the PREDIMED trial, biochemical determinants were available for 5801 participants. Throughout the follow up period, changes in body weight and physical activity were small and did not differ significantly between groups. At baseline, 63.9% (n=3707) met the criteria for metabolic syndrome. After a median follow-up of 4.8 years, metabolic syndrome developed in 960 participants (50%) who did not have the condition at baseline. The risk of developing metabolic syndrome did not differ between control group and the supplemented Mediterranean diets. Reversion occurred in 958 (28.2%) participants who had the condition at baseline with participants on either of the Mediterranean diets significantly more likely to undergo reversion compared to the low-fat control group. Additionally, participants in the Mediterranean group receiving olive oil supplementation also showed significant decreases in both central obesity and fasting glucose levels whilst those supplemented with nuts demonstrated a significant decease in central obesity only.

In contrast to other observational studies assessing the Mediterranean diet, the authors found no beneficial effect of the Mediterranean diet on incidence of new-onset metabolic syndrome. Despite previously reported benefits of the Mediterranean diet, the role of dietary intervention without weight loss was not sufficient to prevent the development of metabolic syndrome in the study population. Limitations of this study include that reversion and incidence of the condition were secondary endpoints making the analyses exploratory. Additionally, the generalisation of the results are limited. Only the first change in metabolic syndrome status was considered which may have been different to long term status. The onset of cardiovascular disease and metabolic syndrome are multifactorial, and whilst it is important to understand the individual roles of different interventions, prevention and treatment strategies that incorporate only dietary changes in the absence of lifestyle medication such as weight management and exercise, will unlikely provide optimal clinical outcomes.
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Author:Tester, Jodie
Publication:Australian Journal of Herbal Medicine
Article Type:Report
Date:Jun 1, 2015
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