Influences of Ketogenic Diet on Body Fat Percentage, Respiratory Exchange Rate, and Total Cholesterol in Athletes: A Systematic Review and Meta-Analysis.

Hyun Suk Lee,Junga Lee

doi:10.3390/ijerph18062912

Abstract

(1) Background: The purpose of the current meta-analysis was to investigate any positive or negative effects of ketogenic diets in athletes and provide an assessment of the size of these effects. (2) Methods: Databases were used to select relevant studies up to January 2021 regarding the effects of ketogenic diets in athletes. Inclusion criteria were as follows: data before and after ketogenic diet use, being randomized controlled trials and presenting ketogenic diets and assessments of ketone status. Study subjects were required to be professional athletes. Review studies, pilot studies, and studies in which non-athletes were included were excluded from this meta-analysis. The outcome effect sizes in these selected studies were calculated by using the standardized mean difference statistic. (3) Results: Eight studies were selected for this meta-analysis. Athletes who consumed the ketogenic diet had reduced body fat percentages, respiratory exchange rates, and increased total cholesterol compared to athletes who did not consume this diet. However, body mass index, cardiorespiratory fitness, heart rate, HDL cholesterol, glucose level, and insulin level were unaffected by the diet. (4) Conclusions: Ketogenic diets had a beneficial effect by decreasing body fat percentage, but athletes with high total cholesterol level need to be monitored when instituting a ketogenic diet. Our study sample size was limited; therefore, additional studies may be needed to confirm the current findings. Further studies need to be conducted on changes in LDL cholesterol, HDL cholesterol, total cholesterol and ratio of LDL to HDL cholesterol.

Highlights

Athletes who require weight control for participation in weight category sports or athletes attempting to improve performance are interested in ketogenic diets
Several ketogenic studies suggested that the beneficial effects of ketogenic diets included reduced weight; reduced fasting glucose and insulin levels; less exercise-induced oxidative stress and inflammation; improved cognition and mood; decreased fat oxidation, and sparing of glycogen stores [2,3]
This review study did not calculate the effect sizes of ketogenic diets on athletic performance

Summary

Introduction

Athletes who require weight control for participation in weight category sports or athletes attempting to improve performance are interested in ketogenic diets. Several ketogenic studies suggested that the beneficial effects of ketogenic diets included reduced weight; reduced fasting glucose and insulin levels; less exercise-induced oxidative stress and inflammation; improved cognition and mood; decreased fat oxidation, and sparing of glycogen stores [2,3]. There were several questions on whether or not the ketogenic diet had any positive or negative influence on athletic body composition, exercise capacity, and physiological factors. These factors included heart rate, insulin level, and levels of cholesterols; the effects of ketogenic diets on these factors in athletes were inconsistent. A previous study reported a negative effect of ketogenic diet on athletic endurance performance [7]. The reasoning was that alterations in the main energy sources from carbohydrate to fat oxidation limited glycogen stores, leading to restrictive muscle

Methods

Results

Discussion

Conclusion