Potassium is crucial to heartbeat regulation, muscle contraction and proper functioning of the nervous system, according to the American Heart Association.

Weight loss is as easy as 24 days of supplements and meal replacement shakes along with a diet high in lean protein, complex carbohydrates and nonstarchy vegetables, says AdvoCare. Its weight-management program, known as the 24-Day Challenge, consists of two phases: the Cleanse and the Max Phase.

Taking a diet pill in conjunction with adopting a healthy lifestyle is a decision that should always be discussed with your doctor. Even if the pill is sold over the counter and does not require a prescription, it may be dangerous for you because of an existing medication or condition.

In past generations, doctors often prescribed amphetamines such as Dexedrine to help people lose weight and feel more energetic. But modern medicine discourages the use of prescription amphetamines for weight loss and energy due to the risk of addiction.

Sixty-eight percent of Americans over age 20 are overweight or obese, according to the Centers for Disease Control and Prevention. And Americans spend more than $40 billion on dieting and weight-loss products each year, many of which are supplements containing stimulants such as caffeine.

Three principal species go by the name ephedra, also known as a Chinese botanical, ma huang. Ephedra, a shrub-like evergreen plant, contains several active alkaloid compounds, including ephedrine, pseudoephedrine and phenylpropanolamine, also known as norephedrine.

Prednisone is a steroid medication commonly prescribed to reduce inflammation in the body. While Prednisone can be helpful in treating your symptoms, it also can have an unwanted side effect: fluid retention that leads to weight gain.

Creatine is a compound that is naturally produced by the body to supply energy to muscles. Creatine is produced by the liver, pancreas and kidneys and it's found in many foods especially meats. Creatine is the main energy suppy for muscles, it helps muscles grow and it fights fatigue in muscles.

After water, green tea can be considered the most popular drink in the world. Asian societies prize the partially fermented leaves of the camelia sinensis, and green tea can be found as a part of many cultural ceremonies in both China and Japan.

Synthroid, also known by its generic name levothyroxine, is taken for hypothyroidism -- a low-functioning thyroid gland. It's a hormone replacement for people who don't make enough thyroid hormone -- the hormone responsible for regulating metabolism.

Lipodrene is a dietary supplement developed by Hi-Tech Pharmaceuticals, marketed as a weight-loss aid. The supplement contains ephedra extract, as well as other ingredients including hoodia, green tea extract and caffeine.

Metformin helps control blood sugar and increase your body's sensitivity to insulin. The drug is available only by prescription and sold under several different brand names, including Fortamet, Glumetza, Riomet, Glucophage and Glucophage XR.