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.
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.
What it actually 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.
Meta-analysis (9 RCTs) · n=408 · healthy women 18 to 73 · Front Nutr
Where it fits
Consistent with what protein does: it supports the muscle side of body composition rather than driving fat loss.
The source
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