Is a vegetarian diet more successful for weight loss than a conventional one?Recently, the news on implications of the vegetarian diets on weight loss caused debates. In the news article, it is claimed that the vegetarian diet twice as effective for weight loss due to elimination of meat from the diet and changing the fat storage mechanisms.
The news article is based on a study that compares the implications of the conventional diet based on energy limitation and vegetarian diet on the weight loss of type-2 diabetes patients.
Results of the studyThe study was conducted on 74 over-weight, type-2 diabetes patients. Participants were divided in 2 groups- one for conventional weight loss diet and one for vegetarian diet- in order to compare the implications of two diets on the loss of weight. Conventional weight-loss diet was applied in parallel with the principles of Europe Diet Researches Association, Diabetes and Diet Study Group. Total energy provided by conventional weight loss diet and vegetarian diet was determined as 5ookcal. Body weight and fat (kg) were measured before the intervention and they were measured and compared on the third and sixth months of the diet.
As a result, individuals who were applied conventional diet lost 3.2 kg on average while individuals who followed the vegetarian diet lost 6.2 kg which is nearly two-times higher.
In the end of the study, changes in the fat tissue under the skin were found similar for both groups. The amount of fat in the connective tissue and muscle tissue was reduced more with the individuals who followed the vegetarian diet. Fat loss in the muscle tissue of individuals who followed the vegetarian diet was found high and it was associated with muscle loss.
Points of concernResults of this study conducted using random control method may mislead individuals and elimination of meat consumption for the weight loss. So, what are the limitations of the study?
There was lower dietary adherence in the conventional group than the vegetarian group: Half of the group that followed vegetarian diet and one third of the conventional diet group showed full adaptation Some of the individuals in the conventional diet group limited energy intake so, the weight loss may be higher for individuals who followed the vegetarian diet.
The authors describe a ‘vegetarian’ diet, but it was also almost vegan: Vegetarian group consumed very little amount of yoghurt as animal-origin product thus, total fat intake was reduced. This extra limitation in the vegetarian diet can explain the excessive increase in the weight loss.
Follow-up only lasted for six months: Monitoring was done for 6 months in this study conducted on individuals with type-2 diabetes. This monitoring period is not sufficient to evaluate long-term effects of these diets over the blood glucose levels or health. In addition, continued muscle and fat loss may have adverse effects on health in the long term.
Results not applicable to everyone: Results of this study does not apply to individuals who do not suffer from type-2 diabetes. In addition, it should not be generalized to all type-2 diabetes patients as it was conducted for a target group that consisted of only 74 individuals.
Scientific facts• World Health Organization (WHO) does not recommend vegetarian diet in the report released for Europe. In addition, more than half of the European countries do not meet 400 g/day vegetable and fruit consumption recommendation of WHO.
• Meat contains fat or saturated fat. WHO recommends limitation of energy taken from the fats in order to solve the obesity.
• In a Cochrane study, it is reported that reducing the consumption of fat of animal-origin thus, total saturated fat intake and replacement of fat with food containing starch or protein would not have a significant effect. It is reported that replacement of saturated fats with polyunsaturated fatty acids may be effective against the reduction of cardiovascular diseases risk.
• World Health Organization, Media centre. Obesity and overweight, June 2016.
• WHO European Ministerial Conference on Counteracting Obesity, Comparative analysis of nutrition policies in the WHO European Region, Istanbul, May 2006.
• Hooper L, Martin N, Abdelhamid A, Davey Smith G. Effect of cutting down on the saturated fat we eat on our risk of heart disease. Cochrane. June 2015.