Protein shakes help women build muscle, not lose fat.
In a 2025 meta-analysis of nine trials in women, pairing a protein supplement with exercise gave small but significant gains in fat-free mass, muscle size and strength, but made no difference to fat mass or body-fat percentage.
Compiled by FitTools from the study cited below
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Published 23 July 2026
- Study design
- Meta-analysis (9 RCTs)
- Sample
- n=408
- Evidence
- preliminary
- Published
- 23 July 2026
Key takeaway
What it shows: Nine trials, 408 women aged 18 to 73. Muscle effects were small (about 0.45 kg fat-free mass) and there was no effect on fat loss; the authors call for more high-quality trials.
Study details
- Design
- Meta-analysis (9 RCTs)
- Sample
- n=408
- Population
- healthy women 18 to 73
- Journal
- Front Nutr
- Published
- 23 July 2026
What they did
Nine trials covering 408 women aged 18 to 73 paired a protein supplement with an exercise programme and tracked body composition and strength.
What they found
Small but significant gains in fat-free mass (about 0.45 kg), muscle size and strength — and no difference to fat mass.
Where it fits
Consistent with what protein does: it supports the muscle side of body composition rather than driving fat loss.
The source
Effects of multi-ingredient protein supplementation combined with exercise on body composition and muscle fitness in healthy women: a systematic review with multilevel meta-analysis. Front Nutr 2025
DOI: 10.3389/fnut.2025.1678433
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