Effects of Low-Carbohydrate Diets Versus Low-Fat Diets on body weight loss and Metabolic Risk Factors: A Meta-Analysis of Randomized Controlled Clinical Trials

Article type
Jin Y1, Li J1, Li X1, Yang K1
1Lanzhou University
Background: Obesity is a 21st-century major public health challenge, not only in Western countries but also in Asian countries. In recent years, there has been growing interest as to whether low-carbohydrate (LC) diets are as effective as, or perhaps better than, traditional low-fat/low-energy (LF) diets for weight management; however, findings from various studies remain controversial, some diet strategies studied for weight loss among LC and LF.

Objectives: To compare the effects of a low carbon or ketogenic diet with a conventional low-fat diet on weight loss in overweight adults.

Methods: We searched sources including the Cochrane Library, PUBMED, EMBASE and Web of Science. We included randomised controlled trials (RCTs) of low carbon diet and low-fat diet on weight loss. Two review authors independently performed study selection, performed data extraction and assessed the risk of bias in the included trials. The primary outcome was body weight change. We used a randomed-effect model to calculate mean differences (MDs) or standardized mean differences (SMDs) for continuous data, with 95% confidence intervals (CIs). We assessed the quality of the evidence using The Cochrane Collaboration Risk of Bias Tool.

Results: We included nine studies with 895 participants. This systematic review and meta-analysis demonstrates that low-carbohydrate diets is more efficient than low-fat diets treatment for obesity. Low-carbohydrate diets led to greater body weight loss. Furthermore, triglycerides decreased more, and high density lipoprotein cholesterol levels increased more, after low-carbohydrate diets. There was no significant difference between low-carbohydrate diets and low-fat diets treatment for changes in levels of total or low density lipoprotein cholesterol.
The most common adverse events after low-carbohydrate diets were constipation, bad breath, dry mouth. Although one subject on the low-carbohydrate diet died from complications of hyperosmolar coma, which was thought to be due to poor compliance with drug therapy for diabetes.

Conclusions: A low - carbon diet is associated with better weight loss than a low - fat diet. But there are more side effects, for example constipation, bad breath, dry mouth.