# Effect of High-Intensity Interval Training and Intermittent Fasting on Body Composition and Physical Performance in Active Women

PMID: 34198554
Journal: International Journal of Environmental Research and Public Health
Published: 2021-06-14
Authors: Martínez-Rodríguez A, Rubio-Arias JA, García-De Frutos JM, Vicente-Martínez M, Gunnarsson TP

## Question

Does intermittent fasting combined with HIIT change body composition and physical performance differently than HIIT alone in active women?

## Summary

In 14 active young women, adding alternate-day time-restricted fasting to an 8-week supervised HIIT block reduced fat mass and improved countermovement jump height more than the same HIIT block without fasting. Other strength and anaerobic power outcomes changed little.

## Population

- Active normal-weight young adult women.
- Sample size: 14
- Age: 27 +/- 6 years
- Sex: Women
- Fitness level: Active
- Health status: Apparently healthy

## Methodology

- Randomized comparative crossover training study
- Two 8-week intervention phases separated by more than 2 weeks
- Supervised exercise sessions in an exercise-testing/training setting
- Randomized and controlled study design.

## Protocol

- HIIT plus intermittent fasting.
- Modality: Cycle ergometer, rowing ergometer, treadmill.
- Work intervals: 30 s all-out.
- Recovery: 30 s passive rest.
- Sets or repetitions: 3 x 10 intervals.
- Intensity: Self-selected maximal effort.
- Session duration: 40 min.
- Frequency: 3 sessions/week.
- Program length: 8 weeks.
- Progression: No formal progression reported.
- HIIT alone.
- Modality: Cycle ergometer, rowing ergometer, treadmill.
- Work intervals: 30 s all-out.
- Recovery: 30 s passive rest.
- Sets or repetitions: 3 x 10 intervals.
- Intensity: Self-selected maximal effort.
- Session duration: 40 min.
- Frequency: 3 sessions/week.
- Program length: 8 weeks.
- Progression: No formal progression reported.

## Outcomes

### Fat mass
Status: improved
HIIT plus fasting reduced fat mass and fat percentage; HIIT alone did not show the same reduction.

Fat mass p=0.003; fat percentage p=0.006 for HIIT plus fasting.

### Jump height
Status: improved
Countermovement jump improved markedly after HIIT plus fasting and was higher than HIIT alone post-intervention.

Within HIIT plus fasting p<0.001; between conditions post-test p<0.001.

### Wingate power
Status: no clear change
Wingate mean and peak power did not show a clear meaningful advantage.

## Practical Insights

- A 30:30 all-out aerobic HIIT structure was feasible under supervision in active women.
- Claims about fasting should be limited because the intervention changed both exercise and eating timing/energy intake.

## Limitations

- Very small sample
- Short intervention
- Active female sample limits generalizability
- Fasting protocol and actual energy intake were not fully controlled

## Safety And Adherence

- No adverse events were reported in the NXML.
- Participants with relevant cardiovascular, cardiorespiratory, or musculoskeletal problems were excluded.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/34198554/) (pubmed)
- [DOI](https://doi.org/10.3390/ijerph18126431) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8296247/) (full text)

## Agent Guidance

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