In a study published in February 2021 in the Journal of the American College of Nutrition, people who followed a low-fat vegan diet lost an average of 6.0 kilograms (13.2 pounds) over 16 weeks. But when these same people followed a Mediterranean diet for the same amount of time, they typically didn’t lose weight. “Because the Mediterranean diet is often touted for weight loss, it was surprising to see that participants experienced very small changes — if any at all — when it came to their weight on this diet,” says the study’s senior author, Hana Kahleova, MD, PhD, the director of clinical research at the Physicians Committee for Responsible Medicine in Washington, DC. RELATED: Why Are Healthy Eating Habits Important?
Mediterranean vs. Vegan Diet: Which Led to Better Health and Weight Results?
For the study, researchers examined the results of both diets in 62 adults who were overweight but had no history of diabetes. Nobody was told to cut or count calories, and participants also weren’t asked to change their normal exercise or medication regimens. Half these participants started the study by following a low-fat vegan diet for 16 weeks. Their eating plan was rich in vegetables, fruits, whole grains, and legumes (such as beans, peas, and lentils) and free of all animal products. The other half of the study participants started with a Mediterranean diet that included everything in a vegan diet but also allowed dairy, fish, and poultry, while limiting saturated fats and red and processed meats. After this initial 16-week period, everyone resumed their normal eating habits for one month. Then they switched diets for 16 weeks to follow the diet they didn’t do before. On the vegan diet, participants ate about 500 calories less each day than they did with their normal eating habits. When they went on the Mediterranean diet, however, their calorie intake didn’t significantly change. And the vegan diet didn’t just help people lose weight. They also lost more fat mass — a total of 3.6 kilograms (7.9 pounds) — compared with only 0.2 kilograms (0.4 pounds) on the Mediterranean diet. Cholesterol levels also improved with the vegan diet, while remaining essentially unchanged on the Mediterranean diet. People following the vegan diet experienced an average reduction in total cholesterol of 0.187 grams per liter and an average decline of 0.153 grams per liter in “bad” LDL cholesterol. While both diets helped lower blood pressure, the effect was more pronounced with the Mediterranean diet, the study also found. Without any medication changes, the vegan diet was tied to a 3.2 mmHg (millimeters of mercury) reduction in systolic blood pressure, compared with 6.0 mmHg for the Mediterranean diet. Both cholesterol and blood pressure levels play a role in heart disease risk, as the Centers for Disease Control and Prevention points out. One limitation to the study is that food intake was self-reported and assessed only at baseline and in the final week of each diet phase, making it possible that the data didn’t give an accurate picture of how people ate. People also tended to lose more weight during the first 16-week diet period, regardless of which diet they started with. RELATED: 21 Tips for Weight Loss That Actually Work
Previous Studies Suggest a Vegan Diet Helps With Weight Loss
The weight loss results with the vegan diet in this study are similar to outcomes experienced by adults with obesity in a study published in November 2020 in JAMA Network Open. After 16 weeks on a vegan diet in this study, participants lost an average of 5.9 kilograms (13 pounds). And an earlier study published in Diabetes Care suggested that a vegan diet may be more effective for weight loss than other ways of eating. This study examined the body mass index (BMI) and eating habits of more than 22,000 men and more than 38,000 women. Vegans had the lowest average BMI — 23.6 — well within the range of 18 to 24.9 that’s considered a normal or healthy weight. The groups with other types of diets all had average BMIs within the overweight range from 25 to 29.9: Vegetarians who ate dairy and eggs had an average BMI of 25.7; vegetarians who ate fish had an average BMI of 26.3; and nonvegetarians had an average BMI of 28.8. RELATED: A Detailed Guide to Following a Plant-Based Diet
A Vegan Diet Isn’t Necessarily Better Than a Well-Followed Mediterranean Diet
Perhaps the biggest disadvantage of a vegan diet is that it may be too restrictive and unsustainable. That may be particularly true for people who are used to a Western-style, meat-and-potatoes approach to meals, says J. David Spence, MD, the director of stroke prevention and atherosclerosis research at the Robarts Research Institute of Western University in London, Ontario. “I think persuading omnivore North Americans to consume a vegan diet in the long term would be pretty hopeless,” says Dr. Spence, who wasn’t involved in the current study. People looking for slow, steady weight loss — and a diet that helps keep those pounds from creeping back on — may do better with a Mediterranean diet, Spence says. They will get the best results from this diet if they focus on cutting out red and processed meats and other unhealthy fats — something that participants in the current study didn’t do very well. In fact, the study participants don’t appear to have followed the Mediterranean diet in an optimal way, Spence says. In the study, people on the Mediterranean diet got a lot of cholesterol and saturated fat (likely from eggs and red meat) that added extra calories to their diet and got in the way of weight loss and other health improvements, Spence says. RELATED: What You Need to Know About the New U.S. Dietary Guidelines
A Well-Designed Mediterranean Diet Is Linked With Several Health Benefits
Other scientific evidence suggests that when followed well, the Mediterranean diet may lead to sustained weight loss. For instance, a study published in April 2016 in the American Journal of Medicine reviewed five clinical trials of the Mediterranean diet and found that people who followed it for at least a year lost up to 10 kilograms (22 pounds). Another study, published in April 2018 in Nutrition and Diabetes, found that people whose eating habits most closely followed a Mediterranean diet had less weight gain, a lower risk of becoming overweight or obese, and accumulated less fat around their midsection than people whose food choices had less in common with a Mediterranean diet. “I think the best diet for most patients is a better version of the Mediterranean diet; vegan might be even better for the very small percentage of patients who would do it,” Spence says. Besides, weight loss is just one piece of overall health, and a Mediterranean diet is linked with additional health perks. For example, this eating style may help stave off health conditions including type 2 diabetes, heart disease, and certain cancers when followed in a healthy way, notes an article published in August 2019 in Nutrients. RELATED: 8 Scientific Health Benefits of the Mediterranean Diet
If You Want to Try a Vegan Diet for Weight Loss, Here’s How
For the quickest weight loss results with a vegan diet, you may want to dive right in the way people did in the study, advises Dr. Kahleova. “In order to see the results quickly, a full immersion is a good approach,” Kahleova says. She recommends an intense three-week kick-start diet from the Physicians Committee for Responsible Medicine. If this sounds too overwhelming, you can still benefit from nudging your diet gradually and incrementally toward a more plant-based eating pattern without completely giving up all animal products, says Vandana Sheth, RDN, CDCES, a private nutrition practitioner in Los Angeles and the author of My Indian Table: Quick & Tasty Vegetarian Recipes. “Food is a very personal process and there is no one-size-fits-all approach,” says Sheth, who wasn’t involved in the new study. “We can encourage people to enjoy more plant-based foods to promote health,” Sheth adds. “The Mediterranean diet may be more approachable and still provides a lot of health benefits.” RELATED: The Best and Worst Diets for Sustained Weight Loss
