Can the Mediterranean diet help me lose weight?

A Mediterranean diet is an eating model based on the dietary patterns of countries surrounding the Mediterranean Sea.¹ Its key components are its high monounsaturated/saturated fat ratio and high intake of plant-based foods. Evidence indicates that a Mediterranean diet is effective at reducing body weight, BMI, and waist circumference (WC).^2-8 While some studies suggest that it is superior to low fat diets,^2-3 they also suggest that its weight reducing effect is similar to other weight loss diets.^2,3,9,10 Nevertheless, studies find overall that the Mediterranean diet has a beneficial weight-reducing effect compared to a usual diet.

A 2018 umbrella review by Dinu et al. assessed 16 medium-to-high quality meta-analyses of randomized controlled trials (RCTs) (n=202 148) that investigated the Mediterranean diet’s effect on multiple health outcomes.⁶ Although only RCTs will be discussed further, it should be noted that they examined meta-analyses of both observational studies and RCTs (N=12 827 449). Studies that compared a Mediterranean diet intervention to a control diet (typically a low-fat diet, low-carbohydrate (carb) diet, or usual American dietary habits) were included. Fifteen studies (n=3525) found that those following a Mediterranean diet had a significant reduction in weight of 1.75 kg (95% confidence interval [CI] [2.86 – 0.64]). Moreover, 12 studies (n=3161) showed a significant reduction in BMI of 0.57 (95% CI [0.93 – 0.21]). Thirty-nine studies found a significant reduction in WC of 0.51 cm (95% CI [0.65 – 0.36]). Therefore, the authors concluded that the analysis showed suggestive evidence for the beneficial effect of the Mediterranean diet on these three components.

A more recent study by Pan et al. made comparisons between multiple weight loss diets through a network meta-analysis.⁴ The authors analyzed ten RCTs (n=921) that involved five dietary patterns: the Mediterranean diet, low-carb diet, high-carb diet, low-fat diet, and regular diet. Directly compared to the low-fat diet, the Mediterranean diet led to significant reductions in weight of 1.18 kg (95% CI [1.99 – 0.37]) and in WC of 0.73 cm (95% CI [1.26 – 0.19]). The authors then ranked the dietary patterns with the P-score, which measures the mean extent of certainty that one treatment is better than its competitors.¹² They found that the Mediterranean diet had the highest P-scores for weight (P-score=0.7922), BMI (P-score=0.7483), and WC (P-score=0.7557); these results indicated that the Mediterranean diet was probably the best dietary intervention for reducing these components.

However, some studies indicate that a Mediterranean diet is similar in effectiveness to other weight loss diets.^{2,3, 9,10} Mancini et al. conducted a systematic review that examined five RCTs (n=998) looking at the long-term effect of a Mediterranean diet in comparison to alternate diets.² These alternate diets included a low-fat diet, a low-carb diet, and the American Diabetes Association diet. The follow-ups ranged from 12 to 48 months. The authors found that the Mediterranean diet was modestly effective at weight reduction with a range of mean changes from 3.8 kg to 10.1 kg. Furthermore, there was evidence that it was significantly more effective for weight loss than a low-fat diet. However, it produced similar weight loss results compared to the other diets in the study. Similar patterns were also seen with regards to BMI and WC. The authors conclude that their findings contribute to the existing literature: that there is no ideal diet for sustained weight loss among overweight and obese individuals.

Shai et al. conducted one of the studies within this systematic review.³ They randomized 322 moderately obese subjects to either a low-fat, restricted-calorie; Mediterranean, restricted-calorie; or low-carb, non–restricted-calorie diet for two years. The daily energy intake significantly decreased for all groups at the 6-, 12-, and 24-month marks compared to baseline. At 24 months, the mean weight changes among the 272 participants who completed the low-fat, Mediterranean, or low-carb intervention were -3.3 + 4.1 kg, -4.6 + 6.0 kg, and -5.5 + 7.0 kg, respectively. Similarly, the mean changes in BMI were -1.0 + 1.4 kg m^-2, -1.5 + 2.2 kg m^-2, and –1.5 + 2.1 kg m^-2, respectively. While all groups lost weight, those on a Mediterranean diet or low-carb diet achieved significantly greater weight loss than those on the low-fat diet (p<0.001). All groups also had significant reductions in WC compared to baseline, but there was no significant difference between groups. Overall, the authors concluded that the Mediterranean diet and low-carb diet are effective alternatives to a low-fat diet for weight reduction.

Based on both systematic reviews and RCTs, evidence suggests that compared to baseline or a usual diet, a Mediterranean diet can lead to weight loss. Furthermore, the more a Mediterranean diet is adhered to, the greater the benefits. ¹¹ Evidence shows that replacing individual dietary components with those characteristic of a Mediterranean diet aids in weight reduction.¹¹ However, many studies also suggest that a Mediterranean diet is only more effective than a low-fat diet at reducing weight. It is similarly effective in comparison to other weight loss diets.

^References

1. Rees K, Takeda A, Martin N, et al. Mediterranean-style diet for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2019;3:Cd009825.
2. Mancini JG, Filion KB, Atallah R, Eisenberg MJ. Systematic review of the Mediterranean diet for long-term weight loss. Am J Med. 2016;129(4):407-415.e404.
3. Shai I, Schwarzfuchs D, Henkin Y, et al. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med. 2008;359(3):229-241.
4. Pan B, Wu Y, Yang Q, et al. The impact of major dietary patterns on glycemic control, cardiovascular risk factors, and weight loss in patients with type 2 diabetes: A network meta-analysis. J Evid Based Med. 2019;12(1):29-39.
5. Ajala O, English P, Pinkney J. Systematic review and meta-analysis of different dietary approaches to the management of type 2 diabetes. Am J Clin Nutr. 2013;97(3):505-516.
6. Dinu M, Pagliai G, Casini A, Sofi F. Mediterranean diet and multiple health outcomes: an umbrella review of meta-analyses of observational studies and randomised trials. Eur J Clin Nutr. 2018;72(1):30-43.
7. Esposito K, Maiorino MI, Bellastella G, Chiodini P, Panagiotakos D, Giugliano D. A journey into a Mediterranean diet and type 2 diabetes: a systematic review with meta-analyses. BMJ Open. 2015;5(8):e008222.
8. Huo R, Du T, Xu Y, et al. Effects of Mediterranean-style diet on glycemic control, weight loss and cardiovascular risk factors among type 2 diabetes individuals: a meta-analysis. Eur J Clin Nutr. 2015;69(11):1200-1208.
9. Fortin A, Rabasa-Lhoret R, Lemieux S, Labonte ME, Gingras V. Comparison of a Mediterranean to a low-fat diet intervention in adults with type 1 diabetes and metabolic syndrome: A 6-month randomized trial. Nutr Metab Cardiovasc Dis. 2018;28(12):1275-1284.
10. Sofi F, Dinu M, Pagliai G, et al. Low-calorie vegetarian versus Mediterranean diets for reducing body weight and improving cardiovascular risk profile: CARDIVEG Study (Cardiovascular Prevention With Vegetarian Diet). Circulation. 2018;137(11):1103-1113.
11. Beulen Y, Martinez-Gonzalez MA, van de Rest O, et al. Quality of dietary fat intake and body weight and obesity in a Mediterranean population: secondary analyses within the PREDIMED Trial. Nutrients. 2018;10(12).