A low-fat vegan diet is more effective for weight loss than a Mediterranean diet, according to a new study that compared the diets head to head. The randomized crossover trial found that the vegan diet was more beneficial for weight, body composition, insulin sensitivity, and cholesterol levels, compared with a Mediterranean diet.
The study randomly assigned 62 participants, who were overweight and had no history of diabetes, to a low-fat vegan diet or a Mediterranean diet.
About the diets
The Mediterranean diet recommended participants consume at least two daily servings of vegetables, 2 to 3 daily servings of fresh fruit, at least 3 weekly servings of fish/seafood, at least 3 weekly servings of beans, lentils, nuts or seeds, and to choose leaner white meats instead of red meat. Participants were asked to limit cream, butter, margarine, processed meats, sugary drinks, sweets and pastries, and processed snacks.
The low-fat vegan diet (10 per cent calories from fat, 75 per cent from carbohydrate) consisted of vegetables, whole grains, beans and lentils, and fruit. Participants were instructed to avoid animal foods and added fats.
About the study
For 16 weeks, one-half of the participants started with a low-fat vegan diet that eliminated animal products and focused on fruits, vegetables, whole grains, and legumes. The other half started with the Mediterranean diet, which emphasized fruits, vegetables, legumes, fish, low-fat dairy, and extra virgin olive oil, while limiting or avoiding red meat and saturated fats.
Neither group had a calorie limit. Participants did not change exercise or medication routines, unless directed by their personal doctors.
As part of the study design, participants then went back to their baseline diets for a four-week washout period before switching to the opposite diet group for an additional 16 weeks.
Study findings
After following each diet for 16 weeks, the study turned up the following results:
- Participants lost an average of 6 kg (about 13 lbs) on the vegan diet, compared with no weight change on the Mediterranean diet.
- Participants lost 3.4 kg (about 7.5 lbs) more fat mass on the vegan diet.
- Participants saw a greater reduction in visceral fat on the vegan diet. Visceral fat is fat that wraps around your abdominal organs deep inside your body. Compared to the fat that lies just underneath your skin (subcutaneous fat), visceral fat is more likely to raise your risk for heart disease, Alzheimer’s disease, Type 2 diabetes, stroke, and high cholesterol.
- The vegan diet decreased blood LDL (“bad”) cholesterol levels; there were no significant cholesterol changes on the Mediterranean diet.
- Blood pressure decreased on both diets, but more so on the Mediterranean diet.
According to the researchers, the Mediterranean diet didn’t result in weight loss due to its inclusion of fatty fish, dairy products, and oils, all of which contribute calories to the diet.
Previous studies have found that both Mediterranean and vegan diets improve body weight and cardiometabolic risk factors, but until now, their effectiveness had not been compared in a randomized trial.
The authors noted that the vegan diet likely led to weight loss, because it was associated with an increase in fibre intake and a decrease in fat consumption, which reduce calorie intake. Besides increasing satiety, eating a low-fat plant-based diet has also been shown to increase calorie-burning after eating.
Even so, it’s important to note that improvements in weight and blood tests were most pronounced on both diets during the first study period than the second study period (e.g., the first diet that participants’ switched to).
In other words, compared to participants’ usual diets before entering the study, following either the Mediterranean or a low-fat vegan diet induced meaningful changes.
Source: Journal of the American College of Nutrition, February 5, 2021.
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