Ketones are a substance naturally found in berries, particularly raspberries. They are an enzyme with a comparable chemical makeup to that of capsaicin and synephrine. The latter are two ingredients that some nutritionists believe have the capability to speed the human metabolism. A raspberry ketone supplement is a popular item among many dieters for this reason.

Capsaicin is a compound found in spicy, hot fare such as peppers. Synephrine on the other hand, is a bitter alkaloid that is regarde...