Body composition changes in physically active individuals consuming ketogenic diets: a systematic review

Abstract

Background

To achieve ideal strength/power to mass ratio, athletes may attempt to lower body mass through reductions in fat mass (FM), while maintaining or increasing fat-free mass (FFM) by manipulating their training regimens and diets. Emerging evidence suggests that consumption of high-fat, ketogenic diets (KD) may be advantageous for reducing body mass and FM, while retaining FFM.

Methods

A systematic review of the literature was conducted using PubMed and Cochrane Library databases to compare the effects of KD versus control diets (CON) on body mass and composition in physically active populations. Randomized and non-randomized studies were included if participants were healthy (free of chronic disease), physically active men or women age ≥ 18 years consuming KD (< 50 g carbohydrate/d or serum or whole blood β-hydroxybutyrate (βhb) > 0.5 mmol/L) for ≥14 days.

Results

Thirteen studies (9 parallel and 4 crossover/longitudinal) that met the inclusion criteria were identified. Aggregated results from the 13 identified studies show body mass decreased 2.7 kg in KD and increased 0.3 kg in CON. FM decreased by 2.3 kg in KD and 0.3 kg in CON. FFM decreased by 0.3 kg in KD and increased 0.7 kg in CON. Estimated energy balance based on changes in body composition was − 339 kcal/d in KD and 5 kcal/d in CON. Risk of bias identified some concern of bias primarily due to studies which allowed participants to self-select diet intervention groups, as well as inability to blind participants to the study intervention, and/or longitudinal study design.

Conclusion

KD can promote mobilization of fat stores to reduce FM while retaining FFM. However, there is variance in results of FFM across studies and some risk-of-bias in the current literature that is discussed in this systematic review.

Keywords:

• Ketosis
• Fat oxidation
• Carbohydrate oxidation
• Low carbohydrate
• High-fat

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12970-021-00440-6.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12970-021-00440-6.

Acknowledgements

The authors wish to acknowledge Drs. Andrew Young and James McClung for their critical review of this manuscript, as well as the subjects and authors of the papers included in this review.

Authors’ contributions

J.L.C., C.T.C., and L.M.M. designed research question; J.L.C. and C.T.C performed literature search; J.L.C., C.T.C., and L.M.M. analyzed and interpreted data; J.L.C. prepared tables and figures; J.L.C. and L.M.M. drafted the manuscript; and J.L.C., C.T.C., and L.M.M. approved final version.

Funding

Supported in part by the US Army Medical Research and Development Command and appointment to the US Army Research Institute of Environmental Medicine administered by the Oak Ridge Institute for Science and Education (to J.L.C.) through an interagency agreement between the US Department of Energy and the US Army Medical Research and Development Command.

Availability of data and materials

All extracted data are presented in this manuscript. The corresponding author may be contacted for any data requests or questions.

Declarations

Ethics approval and consent to participate

This systematic review followed the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions. All participants in the primary manuscripts of this systematic review provided informed written consent. The investigators adhered to the policies for protection of human subjects as prescribed in Army Regulation 70–25, and the research was conducted in adherence with the provisions of 32 CFR part 219. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Army or the Department of Defense. Any citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement of approval of the products or services of these organizations.

Consent for publication

No individuals’ personal data were included in this manuscript.

Competing interests

J.L.C., C.T.C., and L.M.M. have no competing interests associated with this systematic review.

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