Diet pills reviews point out that two categories are more common and available:

• pharmaceutical compounds also known as prescription pills (available on doctor's prescription only)
• dietary supplements also called non-prescription pills (available over the counter). These are typically called weight-loss or dietary supplements.

Pharmaceutical compounds

A diet pill review reveals that there are several main dieting pills on the market:

• Adipex, which works by suppressing appetite
• Bontril, an appetite supressant prescribed along with a healthy diet (a balanced, healthy diet is a diet that provides the so-called RDA of nutrients. RDA is the amount of selected nutrients considered appropriate to meet nutrient needs of healthy people) and an exercise program.
• Didrex (benzphetamine hydrochloride), a sympathomimetic amine similar to an amphetamine (also known as “speed”)
• Ionamin, a popular brand name for the weight-loss diet pill phentermine
• Meridia, a weight-loss diet pill also used in maintaining weight loss
• Phendimetrazine, a sympathomimetic amine, similar to an amphetamine
• Phentermine, the most popular weight-loss diet pill in the United States
• Tenuate (diethylpropion hydrochloride), a sympathomimetic amine similar to an amphetamine
• Xenical, a weight-loss diet pill that targets the absorption of fat in the human body.

Dietary supplements

Supplements which target dieting and losing weight contain one or more dietary ingredients such as vitamins, minerals, botanicals, herbs, amino acids and other constituents. They are available on the market as pills, capsules and powders. They are labeled as dietary supplements. Thus anyone can learn that they are products meant to complete a diet and a certain lifestyle. They are not cures by themselves.

A so-called a new dietary ingredient, now on the market, was not allowed for sale (as a part of a dietary supplement) in the United States before October 15, 1994.