Weight-loss Drugs

Weight-loss drugs or diet pills are used to enhance weight-loss. Most of these diet pills work by both reducing appetite and by stimulating fat metabolism, leading to a reduction in body fat and body weight.

In general there is very little research on the self-directed use of drugs in order to lose weight. The use of non-prescription weight-loss products is especially common among overweight adolescents and adults, but “average-weight” women and men are found to be frequent users as well. For instance, this study estimated 15.2% of adults in the U.S. (women 20.6%/men 9.7%) have used a weight-loss supplements; the highest use was among women aged 18 to 34 years (16.7%). Another group that frequently consumes these types of drugs for weight-loss purposes are bodybuilders.

Most licensed drugs to treat obesity such as ephedrine, fenfluramine and sibutramine have been banned in recent years because of serious harms linked to their use. One exception is Orlistat, which works by interfering with the way that fat is digested and absorbed into the body. Particular concerns of most weight-loss drugs are serious cardiac abnormalities, dysrhythmias and sudden death. Other concerns include psychiatric harms (e.g. depression, aggression and anxiety), insomnia, vomiting headaches, and breathing difficulties.

Another problem with weight-loss products (both legal and illegal) is that studies indicate many are adulterated with other drug substances, contain less or more of the active substance mentioned on the label, or ingredients that have been banned for safety concerns are being replaced by other experimental pharmaceutical drugs. The unknown use of these products may lead to psychosis, cardiovascular problems and even death. For instance, in 2003 a Finish bodybuilder became seriously ill after consuming mislabeled ‘fatburners’ containing a very high amount of 2,4-Dinitrophenol (DNP), an effective but highly toxic substance. A more recent example is the death of a 21-year old UK girl (April 2015) after taking diet pills containing DNP bought over the Internet. Three similar cases have occurred in the UK, and on a global scale there have been 62 published deaths attributed to DNP.

Information on the number of individuals using dietary supplements is important given the growing number of products that contain undeclared active substances.

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Examples of drugs used to lose weight and/or cut body fat:

Name How it works Duration* Route of administration



Clenbuterol is a long acting beta-2 adrenergic agonist. It has been frequently used as a bronchodilator in the treatment of asthma for both humans and horses, but off-label it may be used to increase metabolic rate in order to lose weight. Clenbuterol is also used as a muscle enhancer. 39 hours half-life Oral
2,4-Dinitrophenol (DNP)


Historically DNP is used in dyes, wool preservatives, herbicides, and explosives since the 1930s. Off-label DNP is used for its increased fat metabolism properties in order to lose weight. Exact half-life is unknown but it estimated to be 5 to 14 days. Oral



Off-label ephedrine is used for its increased fat metabolism properties in order to lose weight. 3 to 6 hours half-life Oral
Human Chorionic Gonadotropin (HCG)


HCG administration appeared to diminish and change fat distribution. The theory is that HCG causes the body to preferentially burn stored fat, allowing users to lose more weight than a restrictive diet alone. HCG is also purported to suppress the appetite. Half-life of 2 to 3 days Injection
Laxatives Laxatives are used to stimulate bowel movements. 16 hours half-life Oral
Orlistat Orlistat is a gastrointestinal lipase inhibitor that acts by inhibiting the absorption of dietary fats. 3 hours half-life Oral
Phentermine (e.g., Duromine) Phentermine is an amphetamine type anti-obesity drug. It is an appetite suppressant which ultimately leads to a decrease in weight. In some countries this drugs is medically prescribed as a diet pill to treat obese patients. It is usually prescribed for a short time, between 5 to 12 weeks, as by the time, the effects of it will be gone and increasing the dosage may cause dependence. Besides it weight-loss effects phentermine is also used an enhancement drugs for its relief of fatigue. 6-20 hours half-life Oral
Phenylpropanolamine (PROIN)


Phenylpropanolamine is an appetite suppressant which ultimately leads to a decrease in weight. 3 to 4 hours half-life Oral
Rimonabant Rimonabant is a selective cannabinoid CB1 receptor antagonist. It leads to a decrease in food intake (it suppresses appetite), which ultimately results in weight loss. Half-life of 6 to 9 days Oral




Sibutramine may be used to suppress appetite, reduces energy intake, and increased energy expenditure. 14 to 16 hours half-life Oral
Thyroid hormone (e.g., T3 or T4) Thyroid hormones are associated with weight loss through an increased metabolic rate. Half-life of 5 to 7 days Oral

* The duration can vary depending on the type of drugs.