Slimming is a process of reducing one’s body weight by an individual. Usually, it is the result of thinning tissue fat which provides for a natural energy reserve of mammals. However, a body weight reduction can be caused also by a loss of muscle tissue. It occurs when the total energy input does not cover the energy needs of the organism. We most frequently use the BMI (Body Mass Index) factor to determine whether a person is thin, “in norm” or obese.