by Hazel Smith, MedPage Today Staff
February 26, 2018

Low-calorie lacto-ovo-vegetarian and Mediterranean diets appear to be equally effective in losing weight and reducing of certain risk factors in cardiovascular disease, a randomized trial found.

This study — the first to directly compare the effects of these two eating patterns, the authors said — showed “no significant differences” in terms of the trial’s primary outcomes of weight, body mass index (BMI), and body fat mass, with between-diet differences of 0.11 kg (P=0.95), 0.03kg/m² (P=0.84), and 0.23 kg (P=0.50), respectively.

In terms of body fat mass and overall body weight, participants lost roughly the same amount (3 lb of body fat mass and 4 lb of overall weight, on average). Thus, each diet provided “equally effective results,” the researchers stated online in Circulation.

The lacto-ovo-vegetarian diet includes eggs and dairy but excludes meat and fish, whereas the Mediterranean diet allows for consumption of all food groups, including poultry, fish, and some red meat.

To assess the secondary outcomes, detailed measurements of body weight, body composition, and cardiovascular risk factors such as lipids, markers of glycemia, oxidative stress, and inflammation were taken during the study, at five staggered clinical evaluation periods.

The team reported that noteworthy differentiating factors regarding cardiovascular risk profiles included the fact that the vegetarian diet was more effective in lowering LDL cholesterol (-5.4%, P<0.05), and leukocyte-derived reactive oxygen species (-8.4%, P<0.05), while the Mediterranean diet resulted in greater reductions in triglycerides (-5.9%, P<0.05).

Commenting on the vegetarian diet’s lesser effect on triglyceride levels, the study’s lead author, Francesco Sofi, MD, PhD, of Careggi University Hospital and the University of Florence in Italy, postulated this as due to “the high content of carbohydrate and total fat that occurs when meat and meat products are eliminated from the diet.”

The randomized, open, crossover CARDIVEG (Cardiovascular Prevention with Vegetarian Diet) trial was conducted in Florence from 2014 to 2015 and included 118 healthy but overweight omnivorous participants ages 18 to 75 (mean age of 51.1; 78% of whom were female; BMI ≥ 25).

All participants had a low-to-moderate cardiovascular risk profile (<5% at 10 years), with the simultaneous presence of one or more of the following: total cholesterol levels >190 mg/dl, LDL cholesterol levels >115 mg/dl, triglyceride levels >150 g/dl, and glucose levels 110-126 mg/dl.

Participants were randomly assigned to follow either diet for 3 months, before switching over for the same period of time. Diet compliance rates were high (84.7% at the study’s end), with participants given a 1-week menu plan and detailed instructions on foods that could and could not be included. Participants were instructed not to alter their lifestyle and exercise habits during the study, for which no weight-loss goal was assigned.

The “comparability” of the two diets was highlighted by the authors as a key strength of the study. In addition, an accompanying editorial by Cheryl A. M. Anderson, PhD, MPH, of the University of California, San Diego, pointed to the “healthy dietary pattern rich in fruit and vegetables, legumes, whole grains, and nuts, which focused on diet variety, nutrient density, and appropriate amount of food, and limiting the energy intake from saturated fats.”

Marion Nestle, MPH, PhD, of New York University, who was not involved with the study, likened the equivalence of primary outcomes in this trial to that of the recently published DIETFITS trial of low-fat versus low-carbohydrate diets. (For MedPage Today coverage of the trial, click here.)

“The bottom line,” Nestle told MedPage Today via email, “if you want to lose weight, eat less. If you want losing weight to be easier, eat healthfully.”

Study limitations noted by Sofi et al were the limited duration, small sample size, lack of data on blood pressure levels, and the fact that study participants were from a European country with a “relatively low risk” of cardiovascular disease, meaning that the results may not be applicable to high-risk countries such as the U.S.

Kim Williams, Sr., MD, of Rush University Medical Center in Chicago, also not involved with the study, addressed the question of the short time-span of the study, explaining that the cardiovascular diet debate ought to focus on the criterion of “longevity.”

“We need data on reduction in death, particularly CV death, myocardial infarction and stroke,” Williams told MedPage Today. “There is some definite benefit to reducing weight, particularly reducing hypertension and diabetes, but without evaluation of hard long-term outcomes, we are getting less from this study than we would like.”

Sofi applauded the study for offering multiple pathways for healthful living, writing that the reduction in cardiovascular risk demonstrated by the two diets proves that “people have more than one choice for a heart-healthy diet.”