Very-low-carbohydrate, high-fat diets: Do the risks outweigh the benefits? Original paper

Carbohydrate-restricted diets are becoming increasingly popular, but due to their higher fat content, it is reasonable to question their possible negative effects, particularly in high-risk populations. Are very-low-carbohydrate, high-fat (VLCHF) diets effective or detrimental for high-risk, overweight, and obese people?

This systematic review of eight randomized controlled trials compared the saturated fat (SFA) intakes and measurements of weight, blood glucose, cholesterol, and blood pressure (BP) in overweight and obese adults who ate either a VLCHF diet (≤25% of calories from carbohydrate, >35% of calories from fat) or a low-fat (LF) diet (≥45% of calories from carbohydrate, ≤30% calories from fat). All of the diets were isocaloric (similar caloric intakes) and were moderately calorie-restricted (calorie intakes below maintenance levels). The primary outcomes were weight and blood glucose or lipid profile risk markers (such as LDL and HDL cholesterol and triglycerides). The secondary outcomes were blood pressure and inflammatory markers.

Both diets resulted in significant weight reduction, improved blood glucose levels and inflammatory markers, and lowered blood pressure. The reduction in LDL cholesterol was stronger in the LF diet group, while increased HDL cholesterol and reduced triglycerides were observed in the VLCHF group. The VLCHF and LF interventions both produced some positive outcomes, but despite intensive dietary education and ongoing professional support, half of the RCTs reported noncompliance, and over 25% of all participants included in this review dropped out.