Stacker 2 and Stacker 3 are a new brand of diet energy pills manufactured by NVE Pharmaceuticals that claim to help you burn fat and increase energy.
They contain caffeine, which accounts for the increased energy. They also contain synephrine, structurally similar to ephedra (an FDA-banned substance in diet products) and can increase fat burning in the body. This combination of synephrine and caffeine makes for a potentially harmful drug and may be associated with ischemic stroke and increased blood pressure according to the Mayo Clinic.
The difference between the dietary supplements is that Stacker 3 contains more caffeine. It also contains chitosan, a supplement commonly extracted from the shells of crustaceans, like shrimp and crab that is thought to inhibit the absorption of dietary fat.
“Any weight loss product that claims quick weight loss (more than two pounds a week), eat whatever you want and still lose weight, or all you do is take the pills without having to exercise is a short-lived weight loss promise,” acording to Sarah Krieger, a registered dietitian and national spokesperson for the American Dietetic Association. “Without proper control of food intake and exercise, diet pills are only an effective short term tool.
“Like many diet pills, Stacker contains an appetite suppressant and caffeine, so the idea is to eat less and have a boost of energy, which is supposed to motivate you to exercise,” Krieger said. “The problem is that when a person stops taking the pills, the appetite returns.”