Some over-the-counter diet pills include Alli, chitosan, chromium, green coffee extract and green tea extract, according to Mayo Clinic. Other OTC diet pills are guar gum, hoodia, conjugated linoleic acid and bitter orange.
Alli helps minimize the absorption of dietary fat. Research shows that Alli provides moderate benefits to weight loss. This drug can cause side effects such as loose stools and difficult-to-control bowel movements, notes Mayo Clinic. Chitosan is derived from the exoskeleton of shellfish and helps prevent the absorption of dietary fat. Research on the effectiveness of this pill is minimal. Chitosan may cause an upset stomach, constipation, gas and nausea.
Chromium helps to reduce appetite, increase the number of calories burned and increase lean muscle mass, explains Mayo Clinic. No study shows the effectiveness of this diet pill. Chromium may cause watery stools, dizziness, insomnia, weakness and constipation. Green coffee extract decreases the absorption of sugar in the body, as well as increase fat metabolism. Research indicates that this pill provides possible moderate benefits to weight loss.
Green tea extract reduces the absorption of fat and increases its metabolism. Prolonged use in large doses may cause insomnia, agitation, dizziness, bloating and diarrhea, states Mayo Clinic. There is slight benefit with the use of this pill. Bitter orange helps increase the number of calories burned, as well as suppress appetite. There have been accounts of stroke, heart attack, anxiety and irregular heartbeats with the use of this diet pill.