Fat burners are supplements available over the counter. They claim to help users burn fat and lose weight by increasing metabolism. Metabolism is the rate at which a person burns calories, so increasing metabolism is indeed a sound method of weight loss. Many fat burners also claim to help suppress the appetite and increase energy levels. Common ingredients in fat burners are caffeine, green tea, acai berry, Hoodia Gordonii, HCA, Ephedra, apple cider vinegar, and grapefruit. These herbs and other items are all natural components.