Caffeine is also an ingredient found in many diet pills because of its effects on exercise and digestion. Not only does caffeine help to quell large appetites to some degree, it also acts as a diuretic helping rid the body of excess water weight, it helps burn calories in a small way, and its energy increasing effects are helpful to athletes that wish to continue their exercise regimen despite feelings of tiredness that naturally coincide with strenuous exercise. Of course, these effects are not meant to replace exercise, but to increase the effectiveness of a well rounded exercise and diet plan. Caffeine alone will not be enough to stimulate weight loss.