The Study
Low energy availability increases immune cell formation of reactive oxygen species and impairs exercise performance in female endurance athletes
This study made athletes eat less food for two weeks and saw what happened to their bodies during exercise. Because they switched back and forth between eating enough and not enough, we can say that eating too little probably caused the changes they saw — like feeling more tired and their immune cells making more stress chemicals.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
When female athletes don't eat enough to match their training, their immune cells start making too much harmful stress gas (H2O2), their stress hormone (cortisol) goes up, and their body stops sending immune soldiers to fight during exercise.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 571 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes—this means even after eating properly again, athletes still can't perform at their best, suggesting short-term dieting can leave lasting damage to athletic ability.
- 2After 14 days of eating too little: immune cells made 94% more stress enzyme, exercise made them produce 341% more H2O2, cortisol rose 22%, immune cell movement during exercise dropped 25%, and running performance fell 7.8%.
- 3After 3 days of eating normally: cortisol and immune markers returned to normal, but performance stayed 6.7% worse.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Redox Biology
Year
2024
Authors
J. S. Jeppesen, Hannah G. Caldwell, Lone O. Lossius, Anna K Melin, L. Gliemann, Jens Bangsbo, Y. Hellsten
Related Content
Claims (6)
Athletes who do not consume enough energy to meet their training demands have a higher rate of injury compared to those who do.
When female endurance athletes consume too few calories for 14 days, their bodies release fewer white blood cells during exercise compared to normal conditions, even though baseline levels remain unchanged.
After 14 days of low energy intake, female endurance athletes who consume 52 kcal per kilogram of fat-free mass per day for three days return to normal levels of cortisol and inflammatory proteins in their blood, but their exercise performance does not improve.
In female endurance athletes, consuming too few calories for 14 days increases the production of NADPH oxidase 2 protein and exercise-induced hydrogen peroxide in immune cells, without changing baseline hydrogen peroxide levels or antioxidant enzyme levels.
In female endurance athletes, consuming only 22 kcal per kilogram of fat-free mass per day for 14 days raises resting cortisol levels by 22% and changes the levels of seven plasma proteins involved in immune regulation—five decrease and two increase—without affecting standard inflammatory markers like hsCRP or IL-6.
Female endurance athletes who consume too few calories for 14 days perform 7.8% worse in a 20-minute time trial, and this performance drop does not reverse after three days of eating normally, even though cortisol and inflammatory markers return to normal levels.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.