[en] Gas injection in tokamak discharges has made it possible to raise the electron density, nsub(e), to values well above 10²⁰ m^-3. The most important phenomenon is that the energy confinement time, tausub(E), and the poloidal beta, βsub(theta), increase roughly proportionally to the density, which indicates a change in the prevailing energy loss mechanisms. Rather than considering only the changes in tausub(E) or using elaborate numerical codes, a simple method to evaluate the confinement is introduced here. This method is based on the assumption that the experimental profiles can be approximated by gaussians. Analytic expressions for various plasma quantities as a function of the radius are given. The ohmic power input is compared with the power transported by ion heat conduction for a typical discharge in Alcator. This comparison shows that, within the radius of interest for confinement properties, the plateau-ion heat conduction is the major loss mechanism