Weight and Anthropometric Measures

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Reference: Mancini, J.G., et al., Systematic Review of the Mediterranean Diet for Long-Term Weight Loss. Am J Med, 2016. 129(4): p. 407-415 e4.

One-sentence summary: The Mediterranean diet was efficacious for long-term weight loss in overweight or obese individuals compared with low-fat diets, but not compared with other diets (a low carbohydrate diet or the American Diabetes Association diet).

Study type: A systematic review of 5 RCTs on the Mediterranean diet and weight loss over 12 months or more.

Diet: The Mediterranean diet (6 treatment arms) vs. a low fat diet (4 treatment arms), a low-carbohydrate diet (1 treatment arm), or the American Diabetes Association diet (1 treatment arm).

Outcomes measured: Primary outcomes were weight loss, BMI and waist circumference.

Population: Adults with overweight or obesity who were trying to lose weight. Only 1 RCT assessed the effects of the Mediterranean diet in overweight but otherwise healthy individuals. The remaining 4 RCTs included participants with type 2 diabetes (3 trials), coronary heart disease (1 trial), or a recent myocardial infarction (1 trial). Country of origin was not specified by the authors.

Key results:

A Mediterranean diet at 12 months resulted in:

• Reduction in body weight = range of 3.8 to 10.1 kg weight loss vs. pre-intervention.
  • Significant vs. low-fat diet in 3 of 3 RCTs
  • Not significant vs. other diets in 2 of 2 RCTs
• Reduction in BMI = mean range of -1.0 to -3.3 kg/m² decrease vs. pre-intervention
• Reduction in waist circumference = mean range of -3.5 to -9.3 cm lost vs. pre-intervention

Quality assessment: The quality of trials was assessed using the Cochrane Collaboration’s tool for assessing the risk of bias in RCTs. Most trials had a low or unclear risk of bias for sequence generation (5 trials), allocation concealment (4 trials), and blinding (4 trials).

Limitations:

• Only 5 RCTs were included.
• Heterogeneity in design, population, and comparator meant the authors were unable to statistically pool the data across trials.
• 90% of included participants had established cardiovascular disease or type 2 diabetes, meaning the generalisability of the results to the general population with overweight or obesity who are otherwise healthy is unclear.

The bottom line: The Mediterranean diet resulted in weight loss and a reduction in BMI and waist circumference over the longer-term in overweight or obese individuals. It was more efficacious than a low fat diet, but not compared to other diets.

Other reviews:

Anton, S.D., et al., Effects of Popular Diets without Specific Calorie Targets on Weight Loss Outcomes: Systematic Review of Findings from Clinical Trials. Nutrients, 2017. 9(8).

Bendall, C.L., et al., Central obesity and the Mediterranean diet: A systematic review of intervention trials. Crit Rev Food Sci Nutr, 2017: p. 1-15.

Sayon-Orea, C., S. Carlos, and M.A. Martinez-Gonzalez, Does cooking with vegetable oils increase the risk of chronic diseases?: a systematic review. Br J Nutr, 2015. 113 Suppl 2: p. S36-48.

Esposito, K., et al., Mediterranean diet and weight loss: meta-analysis of randomized controlled trials. Metab Syndr Relat Disord, 2011. 9(1): p. 1-12.

Nordmann, A.J., et al., Meta-analysis comparing Mediterranean to low-fat diets for modification of cardiovascular risk factors. Am J Med, 2011. 124(9): p. 841-51 e2.

Kastorini, C.M., et al., Mediterranean diet and coronary heart disease: is obesity a link? – A systematic review. Nutr Metab Cardiovasc Dis, 2010. 20(7): p. 536-51.

Buckland, G., A. Bach, and L. Serra-Majem, Obesity and the Mediterranean diet: a systematic review of observational and intervention studies. Obes Rev, 2008. 9(6): p. 582-93.