Research
Hormonal
BCAAs, particularly leucine, stimulate muscle protein synthesis via the mTOR signaling pathway, but this effect may be blunted or associated with insulin resistance if circulating BCAA levels are chronically elevated.
BCAAs, especially leucine, do stimulate muscle protein synthesis through the mTOR pathway. However, if you have insulin resistance or obesity, chronically high BCAA levels might contribute to metabolic issues. Focus on a balanced diet and exercise rather than relying solely on BCAA supplements for muscle growth.
GoodQualifiesHIGH confidence
BCAAs stimulate protein synthesis in vitro preparations of skeletal muscle, in which Leu plays the most important roles, and this stimulatory effect is mediated by upregulating the initiation of mRNA translation including TSC2, Rheb, and raptor in the mTOR pathway... A consequence of increased BCAAs levels is the activation of the mTOR/p70S6K pathway and phosphorylation of IRS-1 on multiple serine sites, contributing to IR.
Why this rating
The paper cites multiple studies showing the mTOR pathway's role in both protein synthesis and IR.
Source
Branched Chain Amino Acids: Beyond Nutrition Metabolism
Cunxi Nie et al. · International Journal of Molecular Sciences · 2018
DOI 10.3390/ijms19040954
narrative_reviewCited 770×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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