Thermogenic Fat Burners are the most popular and most widely used category of fat burners. The majority of the products in this line represent a combination of different substances all having metabolic rate & body temperature increase as a primary purpose.  

This effect is often achieved by adding stimulant substances such as caffeine, ephedrine, Synephrine HCL or yohimbe to the supplement formula.

However, if you do not want your energy levels and stamina to depend on any kind of stimulant substances then you can always prefer non-stimulative thermogenics there is a whole variety of those on the market as well.

Side Effects

There are side effects that must be considered when taking  fat burners, they may cause sleeping issues.

Other side effects of common weight loss fat burners include feeling jittery, restlessness, being agitated or excitable.