Six days of low carbohydrate, not energy availability, alters the iron and immune response to exercise in elite athletes
Abstract
Purpose To quantify the effects of a short-term (6-d) low carbohydrate (CHO) high fat (LCHF), and low energy availability (LEA) diet on immune, inflammatory, and iron-regulatory responses to exercise in endurance athletes. Methods Twenty-eight elite male race walkers completed two 6-d diet/training phases. During phase 1 (Baseline), all athletes consumed a high CHO/energy availability (CON) diet (65% CHO and ~40 kcal·kg-1 fat-free mass (FFM)·d-1). In phase 2 (Adaptation), athletes were allocated to either a CON (n = 10), LCHF (n = 8; Results The LCHF athletes displayed a greater IL-6 (P = 0.019) and hepcidin (P = 0.011) response to exercise after Adaptation, compared with Baseline. Similarly, postexercise increases in total white blood cell counts (P = 0.026) and cortisol levels (P 0.05). No differences between CON and LEA were evident for any of the measured biological markers (all P > 0.05). Conclusions Short-term adherence to a LCHF diet elicited small yet unfavorable iron, immune, and stress responses to exercise. In contrast, no substantial alterations to athlete health were observed when athletes restricted energy availability compared with athletes with adequate energy availability. Therefore, short-term restriction of CHO, rather than energy, may have greater negative impacts on athlete health.
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Short-term (≤6 days) investigations in male endurance athletes have reported increases in bone resorption biomarkers with concomitant impairment in bone formation biomarkers, and increased postexercise IL-6 and hepcidin after LCA.
“These studies have reported increases in bone resorption biomarkers 52 53 with a concomitant impairment in biomarkers of bone formation, 53 as well as increased postexercise concentrations of interleukin-6 (IL-6) and hepcidin after LCA.54”
From 2023 international olympic committee's (IOC) consensus statement on relative energy deficiency in sport (REDs) (2023) · cites this paper as [54]
Six studies since 2019 have shown an energy-independent and/or magnifying impact of LCA in the accelerated development of REDs outcomes.
“Six studies since 2019 have shown an energy-independent and/or magnifying impact of LCA in the accelerated development of REDs outcomes.[52][53][54][55][56][57]”
From 2023 international olympic committee's (IOC) consensus statement on relative energy deficiency in sport (REDs) (2023) · cites this paper as [54]
Short-term 6-day carbohydrate restrictions led to small, yet unfavorable changes to iron regulation, immune function, and stress responses.
“These data showed that short-term, 6-day CHO restrictions led to small, yet unfavorable changes to iron regulation, immune function, and stress responses [36].”
From Considerations of Low Carbohydrate Availability (LCA) to Relative Energy Deficiency in Sport (RED-S) in Female Endurance Athletes: A Narrative Review (2023) · cites this paper as [36]
Low carbohydrate availability ranges have not been established based on these criteria for carbohydrate availability, and many studies continue to report carbohydrate intake, using low carbohydrate intake to define intake below current recommendations.
“Nonetheless, LCA ranges have not been established based on these criteria for CHO availability, and many studies continue to report CHO intake, using low CHO intake to define intake below current recommendations [34,35,36,37,38,39,40,41,42,43].”
From Considerations of Low Carbohydrate Availability (LCA) to Relative Energy Deficiency in Sport (RED-S) in Female Endurance Athletes: A Narrative Review (2023) · cites this paper as [36]
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Self-citationDietary protein for athletes: From requirements to optimum adaptation
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Self-citationBurke, L. M., Whitfield, J., Heikura, I. A., Ross, M. L. R., Tee, N., Forbes, S. F., Hall, R., McKay, A. K. A., Wallett, A. M., & Sharma, A. P. (2021) · The Journal of Physiology · doi:10.1113/jp280221 · Cited by 110 · see citing works
Self-citationLow energy availability in female athletes: from the lab to the field
Heikura, I. A., Stellingwerff, T., & Areta, J. L. (2022) · European Journal of Sport Science · doi:10.1080/17461391.2021.1915391 · Cited by 84 · see citing works
Self-citationEffects of an acute exercise bout on serum hepcidin levels
Domínguez, R., Sánchez-Oliver, A., Mata-Ordoñez, F., Feria-Madueño, A., Grimaldi-Puyana, M., López-Samanes, Á., & Pérez-López, A. (2018) · Nutrients · doi:10.3390/nu10020209 · Cited by 64 · cited 1× · see citing works
“Increases in the iron regulatory hormone, hepcidin, have been reported 3 to 6 h after exercise (19,20), resulting in the inhibition of the iron export transporter ferroportin, therefore, potentially limiting iron absorption during the postexercise period.”
BackgroundThe impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes
McKay, A. K. A., Pyne, D. B., Peeling, P., Sharma, A. P., Ross, M. L. R., & Burke, L. M. (2019) · Journal of Sports Sciences · doi:10.1080/02640414.2018.1521712 · Cited by 20 · see citing works
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Mountjoy, M., Ackerman, K. E., Bailey, D. M., Burke, L. M., Constantini, N., Hackney, A. C., Heikura, I. A., Melin, A., Pensgaard, A. M., Stellingwerff, T., et al. (2023) · British Journal of Sports Medicine · doi:10.1136/bjsports-2023-106994 · Cited by 724 · see citing works
Self-citationLodge, M. T., Ward-Ritacco, C. L., & Melanson, K. J. (2023) · Nutrients · doi:10.3390/nu15204457 · Cited by 33 · see citing works
- Authors
- MCKAY, A. K. A., PEELING, P., PYNE, D. B., TEE, N., WHITFIELD, J., SHARMA, A. P., HEIKURA, I. A., & BURKE, L. M.
- Affiliations
- The University of Western Australia (AU)
- University of Canberra (AU)
- Australian Catholic University (AU)
- Ridley College (AU)
- Canadian Sport Centre Pacific (CA)
- Venue
- Medicine & Science in Sports & Exercise
- Published
- 2021-10-25
- Volume
- 54
- Issue
- 3
- Pages
- 377-387
- ISSN
- 0195-9131 (ISSN-L)
- 1530-0315
- OpenAlex
- W3208621791
- Cited by
- 80
- References
- 7
- Citations by year
- 2026: 12 · 2025: 9 · 2024: 32 · 2023: 17 · 2022: 9 · 2020: 1
- FWCI
- 7.61
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Medicine & Science in Sports & Exercise (publishedVersion)
- PubMed (publishedVersion)
- UWA Profiles and Research Repository (UWA) (submittedVersion)
- Topics
- Health Sciences › Medicine › Rehabilitation › Exercise and Physiological Responses
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
- Health Sciences › Medicine › Orthopedics and Sports Medicine › Sports Performance and Training
- Keywords
- low-carbohydrate high-fat diet, energy availability, iron metabolism, hepcidin, interleukin-6, cortisol, inflammation, endurance athletes, race walking, blood glucose, dietary fat restriction, sports nutrition, elite athletes, white blood cell count, exercise stress response
- MeSH terms
- Adult, Humans, Immunity, Iron, Male, Biomarkers, Walking, Athletic Performance, Diet, Ketogenic, Young Adult, Athletes
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