[Ketogenic diet: could the results of scientific studies be misleading?]

Introduction: A significant portion of the average population who is overweight or obese chooses various types of ketogenic diets for weight loss. The scientific and lay literature on this popular fad diet is extensive. Numerous meta-analyses, considered credible sources standing at the top of the evidence pyramid, have examined the effects of ketogenic diets on health. Many of them reported beneficial effects on both anthropometric and blood parameters in cases of obesity and type 2 diabetic patients. However, several confounding factors may modify these favorable results, and many meta-analyses ignore these factors. Objective: The aim of our review is to draw the attention of professionals and those who are enthusiasts of nutrition to these methodological challenges and the interpretational difficulties. Method: The search for meta-analyses was conducted in the PubMed database in September 2023, excluding those focusing on epilepsy treatment or different malignant neoplastic diseases. The keyword used for the search was “ketogenic diet”, exclusively in the titles of the meta-analyses. Results: Of the 18 meta-analyses included in our review, many overlooked confounding factors such as differences in calorie and carbohydrate intake between ketogenic diet and control groups, or the relationship between the types of consumed fatty acids and the blood lipid parameters. Additionally, the presence of nutritional ketosis in groups following the ketogenic diet was not consistently addressed. Conclusion: Despite the widespread literature background often reporting positive results about ketogenic diets, their recommendation is not advisable until well-designed, long-term clinical studies and meta-analyses are conducted, with a greater focus on these confounding factors. Orv Hetil. 2024; 165(7): 260–264.