A lot has been written about the Mediterranean diet and its effect on health, including weight loss and obesity. A new study has been published that examined the effects of this diet on the rate of obesity, and the results seem promising.
I know there have been and will continue to be fad diets that make some outlandish claims for weight loss. In the end, a diet will only work if the calories consumed are less than the calories burned. It’s a simple equation that cannot be violated despite the unscientific claims of many people pushing many diets.
Let’s look at this new science about the Mediterranean diet and obesity.
The Mediterranean diet
The Mediterranean diet is a diet that is common to the eating habits of people living in areas of the Mediterranean, including Greece, Southern Italy, and Spain. The diet generally includes proportionally high amounts of olive oil, legumes, unrefined grains, nuts, fruits, and vegetables. It also includes moderate to high consumption of fish, moderate consumption of dairy products (generally, cheese and yogurt), moderate wine consumption, and low consumption of other types of meat foods.
Unfortunately, there is not a solid definition of this diet. In general, it is low in red meat and high in whole grains, fruits, vegetables, and legumes. But, it does vary from region to region around the Mediterranean.
During the 1940s and 50s, scientists observed that people who consumed the Mediterranean diet seemed to be objectively healthier (broadly defined) and suffered from lower rates of obesity than other populations that ate other types of diets that included refined grains and non-fish meats.
I’ve previously written about this diet concerning cardiovascular diseases, where an extensive study seemed to show positive benefits, although there were some issues in the original research that were eventually corrected. There is also some moderate to good evidence that the diet has a benefit in preventing Alzheimer’s disease, lowering risks for some cancers, and improving blood glucose control for type 2 diabetics.
A systematic review, considered the pinnacle of the hierarchy of biomedical research, provides good evidence that the Mediterranean diet has numerous beneficial outcomes for humans. Another large meta-analysis showed that a Mediterranean diet may reduce the risk of mortality in elderly individuals.
I am usually fairly skeptical of nutritional and diet studies for a few reasons:
- First, these types of studies rely upon observational data — it’s not a clinical trial where the researchers put the subjects in a locked room and only feed them the diet. Data depends upon the memories of the subjects.
- Second, these types of studies may be skewed by confounding data — for example, people who consume Mediterranean diets may have a healthier lifestyle which could include more exercise (like walking), less smoking, or something else.
- Third, correlation does not imply causation. We don’t know if the Mediterranean diet reduces the risk of obesity or if those who aren’t at risk of obesity tend to consume foods in this diet.
Mediterranean diet and obesity paper
In a systematic review published on 30 September 2022, Giovanna Muscogiuri, Department of Clinical Medicine and Surgery, Endocrinology Unit, University Medical School of Naples, Naples, Italy, and colleagues examined the effect of the Mediterranean diet on obesity.
The authors review studies that show that following a Mediterranean diet even without restricting calories is associated with weight maintenance and not weight gain. In other words, this diet does not contribute to obesity.
The study found the following (and I’m just picking the most interesting, the analysis was extensive):
- The Mediterranean diet is an effective tool in reducing body weight, particularly when energy is restricted and in combination with increased exercise.
- A higher Mediterranean diet intake was related to a 30% relative risk decrease in type 2 diabetes incidence during a 20-year follow-up.
- Mean glycated hemoglobin (HbA1c, an indicator of glucose levels in diabetics) was 8.57%, 7.63%, and 6.47% in patients with low, moderate, and high adherence to the Mediterranean diet, respectively. Surprisingly, the high adherence cohort showed a nearly 25% decrease in HbA1c, which is a convincing number.
- Adherence to the Mediterranean exerts several health benefits by improving cardiometabolic risk factors, including glucose and lipid metabolism, obesity indexes, and non-alcoholic fatty liver disease.
- Evidence of protection for the Mediterranean diet was most robust for colorectal, gastric, and breast cancers, especially after the exclusion of alcohol.
The chart above shows all of the health improvements that have been linked to the Mediterranean diet.
Summary
Reading this article made me think that the Mediterranean diet could be a miracle diet that should be recommended to everyone. But we need to temper the enthusiasm a bit.
- It’s not a magic diet that you will suddenly lose weight if you eat nuts, olive oil, and fish. But the Mediterranean diet tends to be higher in fibrous foods and much lower in red meat which can lead to a reduction in obesity. But I have to remind the reader that weight loss still requires that calories consumed are less than calories burned.
- The effect on cardiometabolic issues, such as type 2 diabetes, is very intriguing. The evidence is approaching overwhelming that this type of diet can be useful in managing blood glucose levels and reversing type 2 diabetes (in some individuals, type 2 diabetes is a complex disease).
- The diet’s effect on some cancers is impressive. Again, I don’t want you to think that this diet is a magical cancer prevention one, but, as I’ve written before, a healthy diet does help reduce the risk of cancer.
- The Mediterranean diet is ill-defined, but I believe there is consensus that it includes a lot of fruits, vegetables, whole grains, and nuts; moderate amounts of fish and chicken; and very low amounts of red meat. I think any physician or nutritionist.
I’m basically sold on this diet, with the caveat that it is not a panacea for all that ails you. But it can be a start.
Citations
- Bonaccio M, Di Castelnuovo A, Costanzo S, Gialluisi A, Persichillo M, Cerletti C, Donati MB, de Gaetano G, Iacoviello L. Mediterranean diet and mortality in the elderly: a prospective cohort study and a meta-analysis. Br J Nutr. 2018 Oct;120(8):841-854. doi: 10.1017/S0007114518002179. Epub 2018 Aug 30. PMID: 30157978.
- 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 Jan;72(1):30-43. doi: 10.1038/ejcn.2017.58. Epub 2017 May 10. Review. PubMed PMID: 28488692.
- 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 Aug 10;5(8):e008222. doi: 10.1136/bmjopen-2015-008222. Review. PubMed PMID: 26260349; PubMed Central PMCID: PMC4538272.
- Estruch R, Martínez-González MA, Corella D, Salas-Salvadó J, Fitó M, Chiva-Blanch G, Fiol M, Gómez-Gracia E, Arós F, Lapetra J, Serra-Majem L, Pintó X, Buil-Cosiales P, Sorlí JV, Muñoz MA, Basora-Gallisá J, Lamuela-Raventós RM, Serra-Mir M, Ros E; PREDIMED Study Investigators. Effect of a high-fat Mediterranean diet on bodyweight and waist circumference: a prespecified secondary outcomes analysis of the PREDIMED randomised controlled trial. Lancet Diabetes Endocrinol. 2019 May;7(5):e6-e17. doi: 10.1016/S2213-8587(19)30074-9. PMID: 31003626.
- Lavalette C, Adjibade M, Srour B, Sellem L, Fiolet T, Hercberg S, Latino-Martel P, Fassier P, Deschasaux M, Kesse-Guyot E, Touvier M. Cancer-Specific and General Nutritional Scores and Cancer Risk: Results from the Prospective NutriNet-Santé Cohort.Cancer Res. 2018 Aug 1;78(15):4427-4435. doi: 10.1158/0008-5472.CAN-18-0155. Epub 2018 Jul 26. PubMed PMID: 30049821.
- Muscogiuri G, Verde L, Sulu C, Katsiki N, Hassapidou M, Frias-Toral E, Cucalón G, Pazderska A, Yumuk VD, Colao A, Barrea L. Mediterranean Diet and Obesity-related Disorders: What is the Evidence? Curr Obes Rep. 2022 Dec;11(4):287-304. doi: 10.1007/s13679-022-00481-1. Epub 2022 Sep 30. PMID: 36178601; PMCID: PMC9729142.
- Solfrizzi V, Panza F, Frisardi V, Seripa D, Logroscino G, Imbimbo BP, Pilotto A. Diet and Alzheimer’s disease risk factors or prevention: the current evidence. Expert Rev Neurother. 2011 May;11(5):677-708. doi: 10.1586/ern.11.56. Review. PubMed PMID: 21539488.
