Research
Mixed
Intermittent fasting variants (specifically ADF and TWF) cause significant lean mass loss when combined with energy restriction, unless resistance training and high protein intake are utilized.
If you fast, you must lift weights and eat high protein (>=1.6g/kg). Fasting without these two factors will likely cost you muscle. Modified fasting days should prioritize protein.
GoodSupportsHIGH confidence
Overall, mean differences between the ADF group and the control group in lean mass and fat mass changes were −1.38 and −4.96 kg, respectively... Subgroup analysis showed that in eight-week trials, lean mass and fat mass changes in ADF versus controls were −0.72 and −2.17 kg, respectively
Why this rating
Supported by meta-analyses and specific RCTs cited in the review.
Source
Does Timing Matter? A Narrative Review of Intermittent Fasting Variants and Their Effects on Bodyweight and Body Composition
Alan A. Aragon et al. · Nutrients · 2022
DOI 10.3390/nu14235022
narrative_reviewCited 16×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Intermittent fasting variants (ADF, TWF, TRE) produce weight and fat loss effects equivalent to daily caloric restriction (DCR) when total energy intake is matched, with no inherent metabolic advantage to fasting timing.Good
- Early Time-Restricted Eating (eTRE) offers specific cardiometabolic benefits (glucose tolerance, insulin sensitivity) independent of weight loss, though practical adherence is low.Moderate
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