12:23am Sunday 05 July 2020

Low-fat or low-carb diet? Study shows branded diets have similar level of effectiveness

In a new study led by The Hospital for Sick Children (SickKids) and McMaster University, researchers compared 11 branded diets and found little difference in effectiveness, suggesting that the key to success is sticking to the diet.

The study is published in the Sept. 3 issue of JAMA.

“We wanted to be the first to compare, in an evidence-based fashion, all existing randomized clinical trials of branded diets to determine their effectiveness with regard to weight loss,” says Dr. Bradley Johnston, the study’s lead author and Epidemiologist and Scientist at SickKids, and assistant professor in clinical epidemiology at McMaster University.

Previous research has not directly compared weight loss between the many branded diets. Through a network meta-analysis of nearly 50 randomized controlled trials, the research team developed a novel algorithm to assess the effectiveness of each of the 11 branded diets.  The existing literature used in the study included more than 7,200 overweight or obese individuals. The research team compared weight loss results at six and 12 months including whether caloric restriction, exercise and behavioural support enhanced the weight loss.

Compared to people on no diet, at the six month followup research found that people on a low-carbohydrate diet lost three to four more pounds compared to those on a low-fat diet. After 12 months that difference was gone, rendering 16 pounds lost in total and no difference between the low-carbohydrate and low-fat diet. Additionally, they also found that behavioural support in the diet made a difference at six months, enhancing weight loss by about seven pounds while exercise was significant at 12 months, improving weight loss by about 41/2 pounds.

Johnston notes that this study focused on short-term weight loss outcomes, and did not study the diets’ effects on overall health. Further research should evaluate the long-term outcomes, and explore the role of adherence.  

This research was supported by the Canadian Institutes of Health Research and the Public Health Agency of Canada.

The Hospital for Sick Children (SickKids)

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