Not medical advice: The most effective diet pill that can be found at Walmart, CVS, or Walgreens is Alli, the OTC version of the prescription drug orlistat (Xenical).
Approved by the FDA, research has proven that Alli stops the body from absorbing up to 25% of fat eaten in food. Expect to lose 3 to 5 pounds in addition to what should be shed with exercise and diet alone.
Meals with over 15 grams of fat may result in oily spotting with gas, loose stools, and urgent bowel movements. Itching, loss of appetite, brown urine, light colored stool, yellow eyes or skin may indicate liver injury.
Alli was recently absent from drugstores due to a shortage of its active ingredient orlistat, but is now back on shelves. $316 million of the pill was sold worldwide last year. Nearly 1/3 of the revenue was generated in the U.S.