Effect of High-Intensity Interval Training and Intermittent Fasting on Body Composition and Physical Performance in Active Women
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.
Methodology
- Active normal-weight young adult women.
- 14 participants.
- Cycle ergometer, rowing ergometer, treadmill.
- Work intervals: 30 s all-out.
- Recovery: 30 s passive rest.
- Intensity: Self-selected maximal effort.
- 40 min.
- 3 sessions/week.
- 8 weeks.
- Randomized comparative crossover training study
- Fat mass, Countermovement jump, and Anaerobic power were tracked.
Outcomes
Fat mass
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
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
Wingate mean and peak power did not show a clear meaningful advantage.
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
- No adverse events were reported in the NXML.
- Participants with relevant cardiovascular, cardiorespiratory, or musculoskeletal problems were excluded.