Effects of Whey Protein Alone or as Part of a Multi-ingredient Formulation on Strength, Fat-Free Mass, or Lean Body Mass in Resistance-Trained Individuals: A Meta-analysis.
Level 1 - systematic review of randomized trials
Meta-analysis of randomized controlled trials
PubMed 26403469 · doi:10.1007/s40279-015-0403-y
What was done
A systematic review and meta-analysis of randomized controlled trials evaluated resistance-trained adults (aged 18 and older) undergoing resistance training for at least 6 weeks combined with whey protein alone or as part of a multi-ingredient formulation, compared to an iso-energetic carbohydrate or non-whey protein control. Continuous outcomes for fat-free mass, lean body mass, and maximal strength were pooled using a random-effects model.
What was found
Across 9 randomized controlled trials with 11 treatment arms and 192 participants: - Fat-free mass / lean body mass: Whey or multi-ingredient supplementation showed a small overall benefit versus controls (g = 0.301, 95% CI 0.032 to 0.571). Subgroup effect sizes were g = 0.217 (95% CI -0.113 to 0.547) for whey alone and g = 0.468 (95% CI 0.003 to 0.934) for multi-ingredient formulations. - Lower-body strength: Overall effect was g = 0.316 (95% CI 0.045 to 0.588). In subgroups, whey alone showed g = 0.343 (95% CI -0.016 to 0.702) and multi-ingredient showed g = 0.281 (95% CI -0.135 to 0.697). - Upper-body strength: Overall effect was g = 0.458 (95% CI 0.161 to 0.755). In subgroups, whey alone showed g = 0.343 (95% CI -0.048 to 0.735) and multi-ingredient showed g = 0.612 (95% CI 0.157 to 1.068).
Why it matters
This review shows that whey protein confers small additive improvements in lean mass and strength in resistance-trained individuals compared to iso-energetic controls, with clearer effects observed when delivered in multi-ingredient blends containing creatine.
Limits
The total pooled evidence is small, comprising only 9 studies and 192 participants. Interventions were short (between 6 and 12 weeks, with none exceeding 12 weeks). Supplementation protocols varied substantially in dosage, timing, and multi-ingredient composition, and confidence intervals for isolated whey protein subgroup analyses frequently crossed zero.