Caffeine is an alkoid and is found in guarana, kola nuts, coffee, tea and cocoa beans. It is the most popular drug in the world and is a powerful stimulant to the central nervous system. After caffeine is consumed, it is absorbed into the bloodstream and other body tissues. It takes about half an hour to experience peak concentration in the body. Caffeine provide the energy you need to get through your workouts. If you are trying to lose weight Caffeine has a thermogenic response on the body. It helps to increase the rate of lipolysis and can increase the metabolism. Caffeine has also been found to help suppress the appetite.