After eating protein and doing resistance exercise, young adults increase a muscle protein called LAT1 that helps bring amino acids into muscle cells, but older adults with insulin resistance do not show this increase, which may limit their ability to build muscle.
Claim Context
In young adults, resistance exercise combined with protein ingestion increases skeletal muscle LAT1 transporter levels at 120 minutes, but this response is absent in older adults with insulin resistance, suggesting age-related impairment in amino acid transport capacity.
“In the young adult group, post-exercise LAT1 increased after 120 min (P = 0.027, +206%) versus basal... muscle LAT1 was affected by time (P = 0.431) but not group (P = 0.058) or condition (P = 0.830).”
Evidence from Studies
No evidence studies found yet.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Whether the post-exercise LAT1 response to protein is consistently blunted in older adults with insulin resistance compared to young adults.
A systematic review and meta-analysis of 10+ studies measuring muscle LAT1 expression after protein + resistance exercise in adults aged 65+ with insulin resistance versus young controls, using standardized biopsy timing and quantification methods.
Whether enhancing LAT1 expression improves amino acid uptake and MPS in older adults with insulin resistance.
A double-blind RCT of 80 older adults (65–75 years) with insulin resistance, randomized to receive either a LAT1 activator (e.g., leucine analog) or placebo before 25 g whey + resistance exercise; primary outcomes: muscle LAT1 expression, phenylalanine Rd, and MPS via tracer kinetics at 120 min.
Whether the magnitude of post-exercise LAT1 increase predicts long-term muscle mass retention in older adults.
A 4-year prospective cohort study of 200 older adults (65+ years) measuring post-exercise LAT1 response after standardized protein + resistance exercise every 6 months, tracking lean mass via DXA and adjusting for protein intake and activity.
Whether older adults with preserved vs. impaired post-exercise MPS have different LAT1 responses.
A case-control study comparing 40 older adults (70+ years) with preserved MPS (>15% increase) to 40 with impaired MPS (<5% increase) after protein + exercise, matched for HOMA-IR, measuring LAT1 at 120 min post-intervention.
Whether basal LAT1 levels correlate with insulin sensitivity in older adults.
A cross-sectional analysis of 150 older adults (65–75 years) measuring basal muscle LAT1 and HOMA-IR, adjusting for age, sex, BMI, and physical activity.