We measured the energy loss of 10-, 16-, and 25-MeV oxygen ions in a thin (7.5{mu}g/cm{sup 2}) carbon foil as a function of input charge state (q=4{endash}8). At this thickness, charge-state equilibrium is nearly attained, but the energy losses accumulated over the ion{close_quote}s trajectory are a function of its initial charge state. Using a set of pertinent microscopic atomic collision cross sections computed using the classical trajectory Monte Carlo method, we link these parameters to the observed charge-state dependence on energy loss through a classical transport simulation. This simulation also leads to a prediction of charge-state equilibrium fractions. {copyright} {ital 1998} {ital The American Physical Society}