The Journal of the American College of Nutrition recently published the results of a fascinating study comparing the effects of eating a traditional Mediterranean Diet and a Low-Fat Vegan Diet on body weight and cardio metabolic risk factors. Whilst there is a good deal of evidence to support both diets in terms of their ability to improve these risk factors, the study aimed to ascertain which of the diets was most effective in doing so. The results were interesting and have inevitably provoked a good deal of discussion amongst health professionals and those interested in the field of nutrition, not least because of the huge toll that excess body weight and cardiovascular disease takes on the health of humans worldwide.
Before considering the results of the study and what conclusions may be drawn, let us first take a look at the design of the study. The study was a randomized crossover trial in which 62 overweight adults were randomly assigned to a Mediterranean or vegan diet for a 16-week period. The participants then reverted to their baseline diets for 4 weeks, after which they began the opposite diet for 16 weeks.
What did both diets actually consist of?
The Mediterranean diet participants were asked to consume a specified amount of vegetables, fresh fruits, legumes, fish or shellfish, nuts or seeds, and white meats and they were also asked to use 50g extra virgin olive oil per day. The low-fat vegan diet consisted of vegetables, grains, legumes, and fruits with the aim of obtaining 75% of energy from carbohydrates, 15% from protein, and 10% from fat. Participants could eat as much as they wanted provided they stuck to these guidelines.
At the end of the study, the actual fat intake was calculated at 43% of calories in the Mediterranean group and 17% in the vegan group. The vegan group also consumed around 500 fewer calories per day than the Mediterranean Group, had a higher intake of fibre and lower intakes of saturated fat and cholesterol.
What were the results and what conclusions can we draw?
For those interested in a detailed analysis of the results of the trial, we suggest reading the full study here. The headline results show that a low-fat plant-based diet reduced body weight, fat mass, and visceral fat, increased insulin sensitivity, and reduced levels of total and LDL cholesterol, compared with a Mediterranean diet. Interestingly, systolic and diastolic blood pressure decreased more on the Mediterranean diet, though reductions were seen in both groups.
What does this study tell us? Does it present a compelling argument for following a low-fat wholefood vegan diet first and foremost? Can we position this diet as the gold standard of diets looking at it from the perspective of maintaining and improving cardiovascular and metabolic health? Certainly, there are solid research-backed studies that show the benefits of following a low-fat plant-based diet for heart health and diabetes as eviden