This news release prepared for the Physicians Committee for Responsible Medicine describes a randomized controlled trial involving 74 people with type 2 diabetes that studied the effects of a vegetarian diet on weight loss. The release describes the weight loss effects of the vegetarian diet in comparison to a conventional anti-diabetic diet but it neglects to mention the exercise component of the intervention. This omission makes it seem as if the weight loss effects were solely due to dietary changes. While it’s true that diet was the only major difference between the vegetarian and conventional diet groups, other factors such as exercise may have contributed to the beneficial weight effects in both groups.
The release also neglects to inform readers how long the study lasted — a very big hole. According to the published paper, changes in fat distributions were statistically significant at 3 months but were non-significant at 6 months.
Weight loss is commonly recommended for people with diabetes because it can help manage the symptoms of their disease. It’s also commonly recommended for those at high risk of diabetes to help prevent it. Given the importance of dietary changes in preventing and managing diabetes, research demonstrating the effectiveness of certain diets can greatly influence dietary choices. This could be problematic if the evidence on which these choices are based is premature, which this evidence appears to be.
There may be cost implications in maintaining a balanced vegan or vegetarian diet. This is especially true for people whose conventional meat-based diet currently includes a lot of processed foods and they find they need to shop for expensive veggie burgers and soy-based meals at the Whole Foods or Trader Joe’s to round out their vegetarian diet. It would have been good if the release had at least mentioned there may a cost consideration.
This release describes the weight loss benefits of a vegetarian diet in terms of average weight lost. It states that participants in the vegetarian diet group lost an average of 6.2 kilograms in comparison to participants in the conventional diet group who lost an average of 3.2 kilograms. It also claims those on the vegetarian diet lost more subfascial and intramuscular fat than those on a conventional diet.
The release never tells us how long the study lasted, you have to go to the published report for that. When we did, it wasn’t clear whether the weight loss was maintained at 6 months and beyond. It is very common for weight-loss studies to show that initial weight loss is greater than later weight loss, especially when there is no blinding involved.
The release may encourage people to embark on a vegetarian diet without enough knowledge of the potential downsides. Without careful meal planning, people on vegetarian diets risk not getting enough protein, vitamin B-12, iron, zinc, omega-3 fatty acids. A brief mention of these challenges would have been helpful.
While the news release mentions that this was a randomized controlled trial, it does not go into detail about how various study characteristics may have impacted the findings. Most notably, it does not discuss how well participants adhered to the prescribed diets, or that the sample size was relatively small. It doesn’t say how long the study lasted. It’s well known that short-term weight loss results are difficult to maintain over the long term.
The release also doesn’t mention that there was an exercise component in the trial and the role that exercise played in contributing to weight loss among study participants. In the published study, the researchers noted:
“Our data stress the importance of exercise in weight loss programs to preserve lean mass.”
There was no evidence of disease mongering in this release. However, the fat measures are surrogate markers, which are not necessarily indicative of long term improvement in diabetes, specifically outcomes like death, blindness, leg loss and neuropathy.
The release did not discuss the funding source for the research. However, the organization that the researchers are representing is the Physicians Committee for Responsible Medicine, a group that is a proponent of vegetarian and vegan diets and of dietary management of diseases (where appropriate).
The release does mention one alternative to the vegetarian diet — the anti-diabetic conventional diet which adheres to official recommendations of the European Association for the Study of Diabetes.
The release makes no statement about availability, but it seems at first blush that the diet would be readily available. Then again, perhaps that’s not the case since people who eat a conventional diet containing a lot of processed foods are very likely to turn to processed foods for their vegan or vegetarian meals, as well. Prepared vegetarian foods might be hard to find and expensive, not to mention not very tasty to everyone. To help clarify, the release could have pointed to resources that would help readers eat like participants in the study.
The release describes what the study set out to do — measure changes in weight and in subfascial and intramuscular fat and how these change can impact metabolism. But the study isn’t novel. Numerous studies have been conducted on the effects vegetarian diets have on different types of body fat as well as weight and metabolism.
The release doesn’t rely on sensational, unjustified language.
It does, however, overstate the findings of the research. The first sentence reads:
“Dieters who go vegetarian not only lose weight more effectively than those on conventional low-calorie diets but also improve their metabolism by reducing muscle fat, a new study published in the Journal of the American College of Nutrition has found.”
This is a definitive statement and at no point in the rest of the release does it state that additional research is needed to confirm the findings.