The Study

Hu et al. (2015) studied the effects of a low-carbohydrate diet on body weight, as well as on inflammation, adipocyte dysfunction and endothelial dysfunction in comparison with the more traditional low-fat diet. Those parameters include novel cardiovascular disease markers involved in the initial steps of the disease development. The authors comment, “that increasing evidence suggests that a low-carbohydrate diet may result in both weight loss and improvement in traditional CVD risk factors such as blood pressure, lipids, glucose, and insulin.” Even though there is increasing evidence that low-carbohydrate diets are better than low-fat diets for the improvement of traditional cardiovascular disease markers, the effects of this particular diet on such cardiovascular disease markers are still unclear.

Methods

The 12-month randomized controlled clinical trial was conducted with 148 obese adult subjects (mean age of 46.8 years, 11.5% of men and 51% of African-Americans) from the Greater New Orleans Area. Apart from obesity, these participants were otherwise healthy with no history of diabetes, cardiovascular diseases or chronic renal disease, and had a stable weight for at least six months prior to the beginning of the study. Patients using weight-loss medications or undergoing weight-loss surgery were excluded from the study. Selected subjects were assigned randomly to either a low-carbohydrate diet consisting of an intake of less than 40 grams per day of net carbohydrate (total carbohydrate minus total fiber) or a low-fat diet consisting of a total fat proportion of less than 30% of the daily energy uptake including less than 7% from saturated fat. A dietician followed the patients for the entire year program including many individual and group sessions, as well as behavioral counseling. In order to investigate novel cardiovascular disease markers, blood samples were collected after 12-hour fasting at baseline and every 3 months afterwards.

Results

Approximately 80% of the enrolled patients completed the entire year of the study. The proportion of participants with detectable ketone levels was significantly higher in the low-carbohydrate group than in the low-fat group and no significant differences in physical activity were identified between groups throughout the study. After 12-months, patients in the low-carbohydrate group lost an average of 5.3 kg while patients in the low-fat group lost an average of 1.5 kg. Furthermore, the low-carbohydrate diet group had a significantly higher increase in adiponectin, involved in glucose regulation and fatty acid breakdown, and a higher decrease in the concentrations of intercellular adhesion molecule-1 (ICAM-1), involved in the inflammation process, in comparison to the low-fat group. However, there was no significant change in any other studied novel cardiovascular disease markers between both groups. It is interesting to note that the observed changes in some novel cardiovascular disease markers were not correlated with the weight loss. Finally, as half the participants were Caucasians and the other half were African-Americans, it is important to mention that no notable differences were found between both ethnic groups inside the same diet group.

Conclusion

The main conclusion of this study is described as follows:

“This randomized controlled trial suggests that a 12 month low-carbohydrate diet results in more favorable changes than a low-fat diet in adiponectin and ICAM-1 concentrations, and does not differ from a low-fat diet in reducing other adipocytokines or biochemical markers of endothelial dysfunction in an obese adult population. The two diets had equivalent effects on IL-6, IL-8, and TNF -α concentrations. These findings as a whole suggest that a low-carbohydrate diet is equivalent to, or more effective than, a low-fat diet for improving some novel CVD risk factors.”

The authors of the study state it is important to note that obese adults who lose weight on a low-carbohydrate diet can improve inflammatory status, endothelial function, and adipocyte function, to the same or greater degree than those on a low-fat diet. Also, the authors believe this study is the largest randomized controlled trial to comprehensively examine the effect of a low-carbohydrate diet as compared to a low-fat diet for weight loss on novel CVD risk factors, and importantly, having a racially diverse population with 51% African American participants.

Study Editor

Marie-Christine Brotherton holds a Ph.D. in Cellular and Molecular Biology with specific expertise in Parasitology, Proteomics, Drug Resistance and Genomics. She also holds a MBA with a major in Corporate Social and Environmental Responsibility. She has strong experience with the scientific publication process, including author guidelines requirements, as well as with the medical and social/environmental fields. She can be reached by email at marie-christine.brotherton.1@ulaval.ca

Link to Full Study

Citation

Hu, T., Yao, L., Reynolds, K., Whelton, P. K., Niu, T., Li, S., … & Bazzano, L. A. (2015). The Effects of a Low-Carbohydrate Diet vs. a Low-Fat Diet on Novel Cardiovascular Risk Factors: A Randomized Controlled Trial. Nutrients7(9), 7978-7994.