# Effects of a gluten-free diet combined with sprint interval training on feasibility, performance and health outcomes in non-professional endurance athletes: a pilot trial

PMID: 41210267
Journal: Frontiers in Sports and Active Living
Published: 2025
Authors: Zdzieblik D, Zierke A, Waldvogel T, Gollhofer A, König D

## Question

Is a gluten-free diet combined with standardized sprint interval training feasible, and does it affect performance or health outcomes compared with a mixed diet in non-professional endurance athletes?

## Summary

In healthy male non-professional endurance athletes, a 6-week gluten-free diet combined with supervised sprint interval training was feasible for completers but had lower retention than a mixed-diet comparison. Performance outcomes did not show a clear gluten-free advantage. The sprint protocol is useful background, but the main evidence is about diet feasibility, not HIIT programming.

## Population

- Healthy male non-professional endurance athletes aged 18-50 years.
- Sample size: 20
- Age: Median 24.5 years in GFD and 26.0 years in mixed diet group
- Sex: Male
- Fitness level: Non-professional endurance athletes training 2-5 times per week
- Health status: Healthy; excluded celiac disease, special diets, contraindications to physical activity, unstable weight/eating behavior, and cardiometabolic/renal disease

## Methodology

- Monocentric prospective open-label matched-group pilot trial
- 6-week intervention with testing over about 9 weeks
- University of Freiburg supervised exercise and diet intervention
- Controlled study design.

## Protocol

- Gluten-free diet plus SIT.
- Modality: Diet intervention plus supervised cycle sprint interval training.
- Work intervals: 30 seconds.
- Recovery: 4 minutes.
- Sets or repetitions: 4 sprints weeks 1-2, 5 weeks 3-4, 6 weeks 5-6.
- Intensity: All-out Wingate-style sprints; warm-up/recovery/cooldown at 70-80% HRmax below ventilatory threshold.
- Session duration: Warm-up, 4-6 sprint/recovery repetitions, and cooldown.
- Frequency: 3 sessions per week.
- Program length: 6 weeks; 18 sessions.
- Progression: Sprint repetitions progressed from 4 to 6 across the intervention.
- Mixed diet plus SIT.
- Modality: Habitual mixed diet plus the same supervised cycle SIT.
- Work intervals: 30 seconds.
- Recovery: 4 minutes.
- Sets or repetitions: 4-6 sprints using the same progression.
- Intensity: All-out Wingate-style sprints with same warm-up/recovery/cooldown prescription.
- Session duration: Same as intervention.
- Frequency: 3 sessions per week.
- Program length: 6 weeks; 18 sessions.
- Progression: Same sprint-repetition progression.

## Outcomes

### Retention
Status: mixed
Retention was lower in the gluten-free diet group than the mixed-diet group.

Final analysis: GFD 6/10 retained (60%) and MD 9/10 retained (90%); 15 of 20 enrolled completed.

### Training adherence
Status: improved
Completers attended nearly all sprint sessions in both groups.

Training sessions completed 17 +/- 1 in both groups, p=0.529; key outcome completeness 100%; no major protocol deviations.

### Performance
Status: no clear change
The gluten-free diet did not show a clear performance advantage over mixed diet.

The article reports no clear significant between-group advantage for performance outcomes such as VO2peak, thresholds, substrate oxidation, time to exhaustion, or time trial.

### Body mass
Status: mixed
Weight and BMI changes differed between groups favoring gluten-free diet, but other body-composition and BP outcomes did not clearly differ.

Between-group differences for weight and BMI changes p=0.018 and p=0.026; no significant between-group differences for fat mass, fat-free mass, or blood pressure.

## Practical Insights

- A 6-week progressive 30-second Wingate-style SIT protocol was completed with high attendance among athlete completers.
- A gluten-free diet should not be presented as improving endurance performance in non-celiac athletes based on this pilot.
- Diet interventions can reduce retention even when training adherence among completers is high.

## Limitations

- Small pilot sample with only 15 analyzed completers.
- Non-randomized open-label matched-group design.
- Male endurance athletes only.
- Lower retention in the gluten-free group.
- Self-reported diet and no mechanistic biomarkers.
- Outdoor performance testing was vulnerable to environmental variability.
- No non-training control group.

## Safety And Adherence

- No adverse events or pathological findings were reported via anamnesis/compliance calendar.
- Dropouts were voluntary withdrawals because participants did not continue dietary/training participation.
- Participants were screened for celiac disease, special diets, and contraindications to physical activity.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41210267/) (pubmed)
- [DOI](https://doi.org/10.3389/fspor.2025.1646563) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12589034/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.