A low-fat, plant-based diet is superior in achieving weight loss when compared to a standard Mediterranean diet, according to a study recently published in the Journal of the American College of Nutrition. The randomized crossover trial was conducted by researchers from the Physicians Committee for Responsible Medicine (PCRM)—a group of 12,000 doctors. For the study, overweight participants with no history of diabetes were divided into two groups: one that followed a low-fat plant-based diet and another that followed the Mediterranean diet, (structured around the PREDIMED protocol, which focuses on fruits, vegetables, legumes, fish, low-fat dairy, and extra virgin olive oil, while limiting or avoiding red meat and saturated fats). Participants in each group followed their assigned diets with no calories limited for 16 weeks with no modification in exercise routines or medications. As part of the crossover design, participants then returned to their baseline diets for a four-week “washout” period before switching to the opposite group for an additional 16 weeks. 

“While many people think of the Mediterranean diet as one of the best ways to lose weight, the diet actually crashed and burned when we put it to the test,” study author Neal Barnard, MD, president of PCRM, said. “In a randomized, controlled trial, the Mediterranean diet caused no weight loss at all. The problem seems to be the inclusion of fatty fish, dairy products, and oils. In contrast, a low-fat vegan diet caused significant and consistent weight loss.”

Plant-based weight loss

The study found that participants lost an average of approximately 13 pounds on the vegan diet, compared with no mean change on the Mediterranean diet. Participants lost an average of 7.5 pounds of fat mass and reduced their visceral fat by 315 cm3 on a plant-based diet. A plant-based diet also reduced total and LDL cholesterol levels by 18.7 mg/dL and 15.3 mg/dL, respectively. Participants decreased their blood pressure on both diets, with the Mediterranean diet (6.0 mm Hg compared to 3.2 mmHg on the vegan diet) scoring slightly higher in this metric. 

“Previous studies have suggested that both Mediterranean and vegan diets improve body weight and cardiometabolic risk factors, but until now, their relative efficacy had not been compared in a randomized trial,” study author Hana Kahleova, MD, Ph.D., director of clinical research for PCRM, said. “We decided to test the diets head to head and found that a vegan diet is more effective for both improving health markers and boosting weight loss.”

Researchers propose that the plant-based diet led to weight loss due to a reduction in calorie intake, increase in fiber intake, decrease in fat consumption, and decrease in saturated fat consumption. “If your goal is to lose weight or get healthy in 2021, choosing a plant-based diet is a great way to achieve your resolution,” Kahleova said.

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