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
narrative_reviewCited 16×
Read the paper This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →