Substances such as capsaicin that are found in peppers as well as caffeine and niacin (vitamin B3) are effective to speed up body metabolism. Due to this, the food intake of people who tend to overeat due to various reasons, is automatically restricted when they begin to use circadiyin supplement. Green tea extract is another healthy alternative to a lot of harsher stimulants found in a lot of pills. Some women want to increase their metabolism rate while others might simply want to consume less fat.