Intermittent fasting and continuous energy restriction result in similar changes in body composition and muscle strength when combined with a 12 week resistance training program.
Level 2 - randomized trial
Randomized controlled trial comparing two dietary restriction strategies alongside resistance training
PubMed 35084574 · doi:10.1007/s00394-022-02804-3
What was done
Thirty-four untrained participants completed a 12-week resistance training intervention (two supervised resistance sessions and one unsupervised combined session per week) while following either continuous energy restriction (CERT: 20% daily caloric restriction, n = 17) or 5:2 intermittent fasting (IFT: ~70% restriction 2 days/week, euenergetic 5 days/week, n = 17). Both groups were prescribed ≥ 1.4 g/kg/day of protein. Investigators evaluated changes in body weight, lean body mass (LBM), body fat, thigh muscle size and quality (via ultrasonography and peripheral quantitative computed tomography [pQCT]), dietary intake, and upper/lower body strength and muscular endurance.
What was found
Across both groups, body weight decreased by 4.6% (p < 0.001), body fat decreased by 24.1% (p < 0.001), and LBM increased by 3.7% (p < 0.001), with no significant overall differences between groups, though outcomes differed by sex. Both groups improved thigh muscle size and quality while reducing intramuscular and subcutaneous fat. The CERT group demonstrated a significantly greater increase in muscle surface area on pQCT compared to IFT. Strength and muscular endurance improvements were similar across groups.
Why it matters
This study indicates that 5:2 intermittent fasting is as effective as continuous calorie restriction for fat loss and muscle gain when accompanied by adequate protein and resistance training.
Limits
The sample size was small (34 completers), the trial was retrospectively registered, and unsupervised training sessions were not directly monitored. Specific subgroup values for the reported sex differences were omitted from the abstract, and long-term sustainability beyond 12 weeks was not assessed.
Cited by
- supports Engaging in resistance training prevents muscle loss during intermittent fasting or calorie restriction.