Low Carbohydrate Diets May Not Aid Weight Loss, Yale and Stanford Researchers Find
A new study of low-carbohydrate diets published in this week’s Journal of the American Medical Association shows that carbohydrate content in a person’s diet is not associated with weight loss.
“We found that calorie content and how long you’re on the diet are the factors that predict weight loss, and not carbohydrates,” said co-author Dawn M. Bravata, M.D., assistant professor of medicine at Yale School of Medicine. “This surprised me, because I thought that eating fewer carbohydrates in a diet might produce more successful weight loss. What wasn’t surprising are the findings on calorie content.”
Bravata and her co-authors conducted a study of past research published between 1966 and 2003. They found 107 articles reporting data on 3,268 participants, of whom 663 were on reduced carbohydrate diets (60 grams per day [g/d] or less of carbohydrates). Only 71 had the lowest-carbohydrate diets-20 g/d or less of carbohydrates (the recommended threshold for some of the most popular diets).
The team found that among obese patients, weight loss was associated with longer diet duration, restriction of calorie intake and baseline weight, but not with reduced carbohydrate content. Low-carbohydrate diets had no significant adverse effect on cholesterol, fasting blood sugar, insulin or blood pressure.
“The medical literature is lacking studies about the long-term safety and efficacy of low-carbohydrate diets,” said Bravata. “We need these kinds of studies in order to counsel patients who want to be on the diet.”
According to the article, low-carbohydrate diets have recently resurged in popularity as a means of rapid weight loss, yet their long-term efficacy and safety remain poorly understood. Over the past five years, three books on low-carbohydrate diets collectively sold millions of copies in the United States. Many professional organizations, including the American Dietetic Association and the American Heart Association have cautioned against the use of low-carbohydrate diets. There are concerns that these diets may have serious medical consequences.
Between 1960 and 2000, the prevalence of obesity among adults aged 20 years to 74 years in the United States increased from 13.4 to 30.9 percent, according to the article. Results from the 1998 Behavioral Risk Factor Surveillance Survey indicate that roughly one third of U.S. adults were trying to lose weight at that time, and another third were trying to maintain weight.
Collaborators on the study included lead author Dena Bravata, M.D., Dawn Bravata’s twin sister, at Stanford University School of Medicine; Jane Huang, M.D., Ingram Olkin and Christopher Gardner of Stanford; and Lisa Sanders, M.D., and Harlan M. Krumholz, M.D. of Yale.
Researchers were supported in part by the following organizations: The Robert Wood Johnson Clinical Scholars Program at Yale, the Veterans Administration HSR&D Service Research Career Development Award, the American Medical Association and the National Science Foundation.
Media Contact
Karen N. Peart: karen.peart@yale.edu, 203-980-2222