The Study
Effects of Postexercise Protein Intake on Muscle Mass and Strength During Resistance Training: Is There an Optimal Ratio Between Fast and Slow Proteins?
This study shows that different protein mixes after workouts are linked to similar muscle gains in trained guys, even though some caused bigger spikes in amino acids. We can’t say for sure that the protein caused the results because we don’t know if people were randomly assigned — that’s important to make fair comparisons.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Men who lift weights drank different kinds of protein shakes after workouts for 9 weeks. Some had fast-digesting protein, some had a mix, and some had mostly slow-digesting protein.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 538 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Even though one type caused a bigger amino acid spike, it didn't lead to more muscle or strength over time.
- 2All groups gained similar amounts of muscle and strength.
- 3The shakes with more fast-digesting protein caused a bigger spike in amino acids in the blood right after drinking.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
International journal of sport nutrition and exercise metabolism
Year
2017
Authors
M. Fabre, C. Hausswirth, E. Tiollier, Odeline Molle, J. Louis, Alexandre Durguerian, N. Neveux, X. Bigard
Related Content
Claims (4)
If you eat the same amount of protein and lift weights the same way, it doesn’t matter whether your protein is fast- or slow-digesting—even if it’s from plants like soy—your muscle gains will be about the same.
If you're a guy who lifts weights, drinking a protein shake after your workout with different mixes of fast- and slow-digesting milk proteins — like whey and casein — gives you about the same muscle and strength gains, even if your body processes the amino acids differently.
If you're a guy who lifts weights, drinking a protein shake after your workout with mostly fast-digesting protein gives your body more of a key muscle-building amino acid—leucine—than a shake with mostly slow-digesting protein.
If you're a guy who lifts weights, getting a bigger spike in amino acids after your workout doesn't actually help you gain more muscle or get stronger over time.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.