# Differential effects of intermittent energy restriction vs. continuous energy restriction combined high-intensity interval training on overweight/obese adults: A randomized controlled trial

PMID: 36424927
Journal: Frontiers in Nutrition
Published: 2022
Authors: Xu R, Cao YX, Chen YT, Jia YQ

## Question

Does intermittent energy restriction plus HIIT produce different body composition, lipid, and cardiorespiratory effects than continuous energy restriction plus HIIT or normal diet plus HIIT?

## Summary

In young adults with overweight or obesity, 4 weeks of cycling HIIT combined with either intermittent or continuous energy restriction reduced body size measures and improved some fitness and lipid markers. Intermittent restriction tended to produce larger body-composition changes, but between-diet differences were not statistically significant.

## Population

- Young adults with overweight or obesity
- Sample size: 48
- Age: Mean 21.3 +/- 2.24 years
- Sex: 21 male, 27 female among completers
- Fitness level: Not described as athletes; overweight/obese university adults
- Health status: BMI >=24 kg/m2, without diabetes, major systemic disease, pregnancy, or high cardiovascular risk

## Methodology

- Three-arm randomized controlled trial
- 4 weeks
- University-based exercise and diet intervention
- Randomized and controlled study design.

## Protocol

- Intermittent energy restriction plus HIIT.
- Modality: Cycle ergometer HIIT.
- Work intervals: 3 minutes at 80% VO2max.
- Recovery: 3 minutes at 50% VO2max.
- Sets or repetitions: Five high-intensity cycling bouts separated by low-intensity recovery.
- Intensity: 80% VO2max work and 50% VO2max recovery; HR monitored.
- Session duration: 30-minute interval session with 10-minute warm-up and 10-minute cooldown described.
- Frequency: 5 sessions per week.
- Program length: 4 weeks.
- Progression: Exercise duration individualized to produce about 310 kcal deficit; intensity based on VO2max.
- Continuous energy restriction plus HIIT and normal diet plus HIIT.
- Modality: Same cycling HIIT protocol.
- Work intervals: 3 minutes at 80% VO2max.
- Recovery: 3 minutes at 50% VO2max.
- Sets or repetitions: Five high-intensity cycling bouts.
- Intensity: 80% VO2max work and 50% VO2max recovery.
- Session duration: Same as intervention.
- Frequency: 5 sessions per week.
- Program length: 4 weeks.
- Progression: Same exercise prescription; diet differed.

## Outcomes

### Body composition
Status: improved
Body weight, BMI, body fat percentage, waist circumference, and hip circumference decreased in all groups, with larger numerical reductions in the intermittent restriction group.

Significant time x group interactions for body weight F(2,28)=91.833, BMI F(2,28)=104.405, body fat percentage, waist, and hip circumferences, all p<0.001; post hoc between-diet differences were not significant.

### Lipids
Status: improved
Some lipid markers changed over time, but diet group did not meaningfully alter lipid response to HIIT.

Time effects: total cholesterol p<0.001, triglycerides p=0.002, HDL-c p=0.037; LDL-c not significant.

### VO2max
Status: improved
Absolute and relative VO2max improved over the 4-week HIIT intervention without significant group differences.

Absolute VO2max p=0.001 and relative VO2max p<0.001 over time; no significant between-group differences.

## Practical Insights

- A short, frequent cycling HIIT block can be paired with dietary energy restriction in young adults with overweight/obesity.
- Intermittent restriction may be a viable adherence strategy, but this small 4-week study does not prove superiority over continuous restriction.
- Diet monitoring and make-up sessions were used to support compliance.

## Limitations

- Short 4-week intervention.
- Young university sample limits generalizability.
- Nine randomized participants withdrew because they could not adhere to diet or HIIT.
- Between-group dietary superiority was not clearly established despite numerical trends.

## Safety And Adherence

- Nine participants withdrew during the intervention because they could not adhere to the diet or HIIT; the authors reported no withdrawals due to adverse events.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/36424927/) (pubmed)
- [DOI](https://doi.org/10.3389/fnut.2022.979618) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9678932/) (full text)

## Agent Guidance

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