Research challenges report that Mediterranean is one of the best general weight loss plan

February 16, 2021

4 min read

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Barnard reports having received royalties and royalties from books, articles, and lectures on nutrition and health. In the study you will find all relevant financial information from all other authors.

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US News & World Report recently named Mediterranean Best Overall Diet. However, one study found that a vegan diet improves lipid levels, body weight, and insulin sensitivity better than the Mediterranean diet.

However, the study also showed that the Mediterranean diet was linked to greater reductions in blood pressure, according to researchers.

“Previous studies haven’t compared them yet [Mediterranean and vegan] Diets head to head ” Hana Kahleova, MD, PhD, The director of clinical research at the Medical Committee for Responsible Medicine, a nonprofit that promotes plant-based nutrition and research, told Healio Primary Care, “Our goal was to test the diets in an attempt to determine which diet is more effective. “

Hana Kahleova

In their randomized crossover study, Kahleova and colleagues assigned 62 middle-aged adults with a BMI between 30 kg / m2 and 37 kg / m2 to a Mediterranean or vegan diet for 16 weeks. After measuring a variety of parameters, participants reverted to their base diet for 4 weeks and then followed the opposite diet for 16 weeks. The same parameters were measured again after a 10 hour fast, which coincided with the end of the second 16 week period. People with type 1 diabetes or substance use disorders as well as people who were pregnant or already followed a vegan or Mediterranean diet were excluded.

Kahleova and colleagues wrote that “self-reported general adherence to both diets was high”. Among the participants, 52 completed the study. The researchers found that the total changes in net weight after 16 weeks were 0 kg for the Mediterranean diet and -6 kg for the vegan diet (treatment effect) [TE] = -6 kg; 95% CI, -7.5 to -4.5). The vegan diet was associated with a decrease in insulin resistance, as measured by the insulin reactivity of the homeostasis model (TE = -0.7; 95% CI, -1.8 to +0.4), and an increase in oral glucose-insulin sensitivity (TE = +35.8 ml) / min / m²; 95% CI, +13.2 to +58.3); However, the Mediterranean diet was not associated with significant changes in these parameters. The predicted insulin sensitivity did not change significantly in either group.

In addition, among all participants with no drug changes, the researchers reported that total cholesterol decreased by 18.7 mg / dL and LDL cholesterol decreased by 15.3 mg / dL with the vegan diet, but there were no significant changes related to the Mediterranean diet (TE =) -15.6 mg / dl; 95% CI, -24.6 to -6.6). The systolic and diastolic blood pressure decreased with the Mediterranean diet by 9.3 mm / Hg and 7.3 mm / Hg (TE = +5.9 mm Hg; 95% CI; +1 to +10.9]compared to 3.4 mmHg and 4.1 mm Hg with the vegan diet (TE) = +1.8 mm / Hg; 95% CI, -4.6 to +8.1).

“We weren’t surprised to see people seeing improvements in the plant-based diet,” said Kahleova. “Previous epidemiological studies have shown that people who follow a plant-based diet tend to have lower body weight and fewer cardiometabolic risk factors compared to other diets.

“However, since the Mediterranean diet is widely touted for weight loss, it was surprising to see that the participants in our study did not lose any significant weight on this diet,” she continued. “However, previous clinical studies have shown that significant weight loss on the Mediterranean diet involves either additional exercise or calorie restriction, confusing the effects of diet changes. In our study, every diet was tested without these additional factors that likely played a role in the results. “

Neal Barnard

Neal Barnard, MD, The President of the Medical Committee for Responsible Medicine and co-author of the study said in a press release that the Mediterranean diet “crashed and burned when we put it to the test” to serve as a weight loss tool.

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David S. Seres, MD, ScM, PNS, FASP

Although the study was properly conducted by Barnard and colleagues, its interpretation must be greeted with a grain of salt. Pun intended.

While their results are hopeful that the patients in this short-term study lost more weight and improved their cholesterol and insulin levels, questions remain as to whether the patients’ weight loss is sustainable. In addition, the authors did not control the number of calories consumed. The changes in cholesterol they report are consistent with the great weight loss. However, it is inappropriate to generalize that a vegan diet is healthier based on a relatively short-term study like this one.

It is also important to make readers aware that only three of the 12 authors are academic and that 10 of the 12 are members of the Medical Committee for Responsible Medicine, which has long supported the vegan diet. Long-term commitment to an idea can increase the risk of inadvertently skewing the design or interpretation of a study.

Another point I want to make is that healthy markers don’t always lead to completely healthy individuals. For example, there are many people with low cholesterol who have had a heart attack for reasons other than their cholesterol levels. Therefore, based on a person’s cholesterol level alone, you cannot assume that that person will have a heart attack or not.

To find out if the changes Barnard and colleagues described lead to better health, you will need a much longer study because the health effects of dieting are slow to manifest themselves. Longer and more comprehensive studies would be needed to determine the magnitude of the effects, how many people would have to follow a strictly vegan diet to achieve the desired result, and how long they would have to follow that diet to be able to determine if it is worth the effort and whether people can stick to the diet without harm. So far, the diet-related impact on actual outcomes, such as the incidence of heart attacks, has been minor, even over an extended period. I can imagine that adhering to a strictly vegan diet would have a relatively small effect with a lot of effort.

Hence, and unfortunately, there is not much that doctors can take away from this study.

David S. Seres, MD, ScM, PNS, FASP

Diet Section Editor, UpToDate
Former Chairman of the American Society for Nutrition’s Medical Nutrition Council
Professor of Medicine, Institute for Human Nutrition
Director of Medical Nutrition and Associate Clinical Ethicist at Irving Medical Center, Columbia University

Disclosure: Seres does not report any relevant financial information.

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Heather Hutchins-Wiese, PhD, RD

Barnard and his colleagues are members of the Medical Committee for Responsible Medicine, a nonprofit group that promotes vegan nutrition and is funding the study. This potential bias must be taken into account when interpreting the study methodology and the study results.

Her main result was greater weight loss on the low-fat vegan diet compared to the Mediterranean diet. This finding is not surprising, even in an ad libitum intake study, since a low-fat vegan diet is a more restrictive diet compared to the Mediterranean diet. Short-term diet comparisons like this one usually favor the more restrictive diet plan, but when the diets are studied for a year or more we see similar weight loss overall.

This leads us to the more important question of what is more practical for a patient to follow over the long term. Both diets are beneficial for cardiometabolic results. Both encourage the consumption of grains, vegetables, fruits, and legumes. The low-fat vegan diet restricts all animal products and limits oils with a goal of 10% of the energy from fats. One of the pillars of the Mediterranean diet is the consumption of olive oil and the use of herbs and spices to flavor foods. The PREDIMED diet intervention, adopted by Barnard and colleagues for their Mediterranean diet recommendations, also encouraged nut consumption to favorably influence the ratio of monounsaturated to saturated fatty acids. A moderate intake of fish, eggs, poultry, and wine with a limited intake of red and processed meats and sweets is also recommended. As we learn more about precision nutrition, we may be able to suggest one diet over another based on genetic interactions.

Regardless of our genetic makeup, we are all human and have personal preferences and habits that are difficult to change in the long run. The best way to help a patient change behavior is to use a medical team approach. Talk to the patient, learn about their values ​​and goals, what they like to eat, what they are willing to change, and work from there. Successful behavior changes can occur, but support, knowledge, and skills are required. and that happens to more than just a diet recipe.

Heather Hutchins-Wiese, PhD, RD

Associate Professor of Dietetics and Human Nutrition Programs at Eastern Michigan University

Disclosure: Hutchins-Wiese does not report any relevant financial information.

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