The quasi-Gaussian entropy theory has been applied to reproduce the temperature dependence of the internal energy, pressure and isochoric heat capacity of a molecular dynamics simulated Lennard-Jones (LJ) fluid at density rho=1 (reduced units). The results show that the gamma state level of the theory is an excellent approximation, able to predict the behavior of these properties over a large temperature range. This application of the theory to the simulated LJ fluid confirms previous results, obtained using experimental fluid data, and shows that the gamma state level of the theory, in combination with molecular simulation techniques, can be used as a general model to obtain accurate and physically consistent equations of state for fluid systems.