The Stacker family of products (including Stacker 2, Stacker 3 and Stacker YJ Stinger) is one of the big sellers in the popular fitness supplement market. Their tag line claims it is "the world's strongest fat burner", helping to burn fat, cut cravings and boost energy. Other claimed benefits of Stacker include increasing mental focus; enhancing physical endurance and helping you enjoy more productive workouts. The various formulations are also said to suppress your appetite, increase metabolic response and help you transform your body. However, be a little skeptical of any product that suggests you can have your cake, eat it too and still shed the pounds.
Like most of the "thermogenic" fat burners out there, Stacker's special formula contains ingredients like kola nut, yerba mate, gurana, white willow bark and green tea - essentially a high caffeine and aspirin-like cocktail; which may indeed have some of the claimed effects, but is not a recommended long-term solution to losing weight, getting fit or improving mental clarity. Other formulations include extracts of herbal ephedra (always an ingredient to be cautious of), chitosan (which helps to reduce the body's absorption of fat - Stacker claims this helps calories pass through you), and chromium picolonate (which can help regulate blood sugar levels).
While some of these ingredients sound promising, not enough independent study has been conducted on these formulations. The list of reported side-effects includes dizziness, sleeplessness, tremors, nervousness, headache and heart palpitations. Perhaps old fashioned diet and exercise is a better approach.