Branched-chain amino acids (BCAA) positively associated with insulin sensitivity in individuals without diabetes.
Muscle volume was important for circulating levels of BCAA and tyrosine (Tyr).
BCAA correlated with increased fasting blood glucose and fasting immunoreactive insulin (IRI) levels.
Serum BCAA and Tyr levels were higher in men than in women.
Tyr did not affect insulin sensitivity but was associated with fasting IRI levels.