Fractional synthetic rate

A fractional synthetic rate (FSR) is the rate at which a precursor compound is incorporated into a product per unit of product mass.^[1] The metric has been used to estimate the rate at which proteins, lipids, and lipoproteins are synthesized within humans and other animals.^[1][2] The formula used to calculate the FSR from a stable isotope tracer experiment is:^[1]

${\displaystyle FSR={\frac {\color {Blue}{\text{initial rate of change in product enrichment}}}{\color {Green}{\text{initial precursor enrichment}}}}}$