# Impact of Intermittent Fasting Combined With High-Intensity Interval Training on Body Composition, Metabolic Biomarkers, and Physical Fitness in Women With Obesity

PMID: 35694163
Journal: Frontiers in Nutrition
Published: 2022
Authors: Batitucci G, Faria Junior EV, Nogueira JE, Brandão CFC, Abud GF, Ortiz GU, Marchini JS, Freitas EC

## Question

Does intermittent fasting combined with HIIT improve body composition, metabolic biomarkers, and physical fitness in women with obesity?

## Summary

This randomized trial in women with obesity found that 8 weeks of supervised circuit HIIT plus 5:2 intermittent fasting reduced weight/BMI and body fat while increasing fat-free mass. Dropout was high, especially in fasting-only and exercise-only groups, and some fasting-only dropouts reported dizziness and headaches.

## Population

- Women with degree-one obesity
- Sample size: 36
- Age: Mean 32.2 +/- 4.4 years
- Sex: Women
- Health status: Obesity; major cardiometabolic and other conditions excluded

## Methodology

- Randomized intervention trial
- 8 weeks
- University gym with dietary counseling
- Randomized and controlled study design.

## Protocol

- Supervised circuit HIIT.
- Modality: Mixed gym circuit.
- Work intervals: 30-45 seconds.
- Recovery: 30-15 seconds.
- Sets or repetitions: 9 exercises, 2 laps.
- Intensity: 70-85% HRmax.
- Session duration: 25 minutes.
- Frequency: 3 sessions/week.
- Program length: 8 weeks.
- Progression: Work/rest progressed every two weeks.
- 5:2 intermittent fasting or HIIT only.
- Modality: Diet-only IF or exercise-only HIIT.
- Sets or repetitions: IF two nonconsecutive fasting days/week.
- Intensity: IF days about 25% daily energy intake.
- Session duration: IF eating window 6 hours followed by 18-hour fast.
- Frequency: IF twice/week.
- Program length: 8 weeks.

## Outcomes

### Weight/BMI
Status: improved
Weight and BMI decreased only in IF+EX.

Weight p=0.012; BMI p=0.031.

### Body fat/FFM
Status: improved
IF+EX and EX reduced body fat and increased fat-free mass.

Body fat IF+EX -4%, p<0.001; EX -2.3%, p=0.043; FFM IF+EX +3.3%, p<0.001; EX +2%, p=0.043.

### Fitness
Status: improved
Aerobic capacity and strength improved in exercise groups.

### Adherence
Status: worse/safety concern
Dropout was high, especially in fasting-only and exercise-only groups.

IF+EX 25%, EX 45%, IF 50% dropout.

## Practical Insights

- A progressive 25-minute circuit is adaptable, but fasting co-intervention complicates claims.
- Fasting symptoms and dropout should be tracked explicitly.

## Limitations

- Short 8-week intervention.
- High dropout and small final sample.
- Baseline group imbalance.
- Nonexercise activity not monitored.
- IF group did not complete physical tests.

## Safety And Adherence

- Exercise-related adverse events were not reported.
- Three intermittent-fasting dropouts reported low diet acceptance due to dizziness and headaches.
- Participants were screened to exclude diabetes, hypertension, dyslipidemia, heart disease, osteoarthritis, gastritis, regular medication, smoking/alcoholism, and malaise during prolonged fasting.
- Exercise sessions were fully supervised with HR and RPE monitoring; dropout was high.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/35694163/) (pubmed)
- [DOI](https://doi.org/10.3389/fnut.2022.884305) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9178202/) (full text)

## Agent Guidance

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