The Effects of Concurrent Training Combined with Low-Carbohydrate High-Fat Ketogenic Diet on Body Composition and Aerobic Performance: A Systematic Review and Meta-Analysis

Abstract

(1) Background: Recently, studies have emerged to explore the effects of concurrent training (CT) with a low-carb, high-fat ketogenic diet (LCHF) on body composition and aerobic performance and observed its benefits. However, a large variance in the study design and observations is presented, which needs to be comprehensively assessed. We here thus completed a systematic review and meta-analysis to characterize the effects of the intervention combining CT and LCHF on body composition and aerobic capacity in people with training experience as compared to that combining CT and other dietary strategies. (2) Methods: A search strategy based on the PICOS principle was used to find literature in the databases of PubMed, Web of Science, EBSCO, Sport-discuss, and Medline. The quality and risk of bias in the studies were independently assessed by two researchers. (3) Result: Eight studies consisting of 170 participants were included in this work. The pooled results showed no significant effects of CT with LCHF on lean mass (SMD = −0.08, 95% CI −0.44 to 0.3, p = 0.69), body fat percentage (SMD = −0.29, 95% CI −0.66 to 0.08, p = 0.13), body mass (SMD = −0.21, 95% CI −0.53 to 0.11, p = 0.2), VO2max (SMD = −0.01, 95% CI −0.4 to 0.37, p = 0.95), and time (or distance) to complete the aerobic tests (SMD = −0.02, 95% CI −0.41 to 0.37, p = 0.1). Subgroup analyses also showed that the training background of participants (i.e., recreationally trained participants or professionally trained participants) and intervention duration (e.g., > or ≤six weeks) did not significantly affect the results. (4) Conclusions: This systematic review and meta-analysis provide evidence that compared to other dietary strategies, using LCHF with CT cannot induce greater benefits for lean mass, body fat percentage, body mass, VO2max, and aerobic performance in trained participants.

Methodological Challenges and Confounders in Research on the Effects of Ketogenic Diets: A Literature Review of Meta-Analyses

“…If the selected meta-analyses are reviewed in terms of caloric intake [11,24,26,29,31,32,34,44,57], several observations can be made. When we further examined the data from the six included publications in Gohari et al's meta-analysis [29], we found that information on caloric intake was either completely missing [59] or that the ketogenic and control groups consumed different amounts of calories [60].…”

“…In the case of Wang et al's meta-analysis [34], two of the included publications [61,62] prescribed more calories for the ketogenic group than for the control group.…”

“…Regarding carbohydrate intake and the presence of nutritional ketosis in the included meta-analyses [22][23][24][25][31][32][33][34]36], the following issues arose.…”

Ketogenic diets, exercise performance, and training adaptations

“…Regarding exercise performance, the most recent systematic reviews, including or not meta-analysis, showed that the ketogenic diet does not produce better effects compared with carbohydrate-based diets in both aerobic (e.g. cycling and running) and strength performances [7 ▪ ,9] and seems to have no effect in improving endurance performance even when combined with concurrent training [8].…”

“…Over the decades, several studies have been conducted about the effects of the ketogenic diet on exercise performance in different modalities and exercise modes, and on the body composition in diverse populations. Concerning this issue, there were several studies with meta-analyses published recently [7 ▪ ,8–10]. They all showed no advantage of the ketogenic diet over normal/high carbohydrate-based diets on physical performance.…”