Diet pills are medications that can help individuals lose weight when they’re used in combination with diet and exercise plans. Some diet pills are available over the counter. Others require a prescription. The pills work by increasing metabolism, reducing appetite or changing how the body burns calories.
Over-the-counter diet pills aren’t always evaluated for safety or efficacy. Many people don’t realize that these herbal supplements don’t have to be tested before they’re sold in grocery or health stores.
Some prescription weight-loss drugs are controlled by the Drug Enforcement Administration because of their potential for abuse. Many of these diet pills contain amphetamines or chemicals similar to amphetamines. They’re approved only for short-term weight management because long-term use may increase the risk of dependency or addiction.
Anti-obesity drugs approved by the Food and Drug Administration include:
Diet pill misuse is associated with eating disorders, according to several studies. Anorexia, bulimia and other eating disorders are serious mental health conditions. People with eating disorders often practice dangerous behaviors, such as purging, limiting food intake and binge eating.
They may also take diet pills without a prescription to lose weight. Or they may take higher doses than prescribed. Misusing diet pills increases the risk of several life-threatening health complications.
The oldest weight-loss pills contain amphetamine or similar compounds. Amphetamine is a stimulant that’s found in some attention-deficit/hyperactivity disorder medications, such as Adderall. It’s also chemically similar to methamphetamine, a drug that was once used as a weight loss medication. Today, methamphetamine is more likely to be found on the street than in a doctor’s office.
In the past 30 years, companies have developed diet pills that don’t contain amphetamine. They’re considered less addictive than drugs with amphetamines, but they also have the potential to cause other side effects.
Many over-the-counter diet pills claim to help individuals lose weight. However, these herbal supplements aren’t subject to FDA approval. Many are sold over the counter without any proof that they’re safe or effective.
Amphetamine-based diet pills — diethylpropion, benzphetamine, phentermine and phendimetrazine — decrease appetite, which often leads to weight loss. The drugs aren’t considered as addictive as amphetamine, but the FDA has issued warnings about their abuse and addiction potential. The agency has limited their use to “a few weeks.”
Fenfluramine, an amphetamine-based diet pill formerly sold under the name Pondimin, grew in popularity in the 1990s. Doctors sometimes prescribed it in combination with phentermine (Adipex) as a treatment known as fen-phen. The FDA withdrew fenfluramine and its derivative dexfenfluramine (Redux) from the market after the products were linked to heart problems.
Phentermine is still available today. It’s one of the most commonly used weight loss drugs in the United States. A 2014 study published in the International Journal of Obesity concluded that phentermine abuse and dependence didn’t occur among patients treated for obesity.
The authors of the study also found that phentermine didn’t cause cravings or withdrawal symptoms. However, the lead author of the study had financial ties to several companies that sell products containing phentermine. Critics of the study say there isn’t enough data to prove that the drug isn’t addictive.
The DEA classifies phentermine and diethylpropion as Schedule IV controlled substances, meaning they have some potential for abuse or dependence. Benzphetamine and phendimetrazine are Schedule III controlled substances, meaning they have a higher potential of abuse and dependence than Schedule IV substances.
Another popular amphetamine-based drug called mazindol is listed as a Schedule IV controlled substance. Mazindol was sold under the brand name Sanorex. The company that sold the medication discontinued it in the United States in 1999.
In general, weight-loss drugs that don’t contain amphetamine are believed to be less addictive than drugs that are made with the potent stimulant. Like all diet pills, they promote weight loss when used in combination with an exercise and diet plan.
However, individuals with eating disorders may misuse weight-loss drugs by using them more often or longer than prescribed. The medications may also cause undesirable side effects.
FDA-approved weight loss medications include:
Most diet pills are prescribed for a few weeks or months. However, phentermine/extended-release topiramate, lorcaserin and orlistat may be prescribed for life.
Orlistat is the only FDA-approved weight-loss medication that’s available over the counter. It’s sold under the brand name Alli in 60 milligram doses. Xenical, the prescription version of orlistat, comes in 120 milligram doses.
Herbal supplements, such as green tea extract, garcinia cambogia extract and raspberry ketones, are sometimes added to weight loss pills. However, no studies have proved that the supplements help people lose weight. Some supplements, such as green tea extract, may have other health benefits and few side effects. However, no one should take an herbal supplement without consulting with their doctor.
Several other over-the-counter weight loss pills, including Hydroxycut, contain large amounts of caffeine. Caffeine may have a small impact on weight loss, according to several studies. However, large amounts of caffeine can lead to headaches, sleep problems, rapid heartbeat and stomach issues.
Some diet supplements have been associated with health problems in the past. In 2009, the FDA warned that Hydroxycut products were associated with serious liver problems. The drug was recalled and reformulated after the FDA warnings. In 2014, the FDA recalled a weight loss pill called OxyElite Pro after it was linked to a nonviral hepatitis outbreak.
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In general, people seeking to lose weight or to maintain low body weight are more likely to misuse diet pills than other people. Some pills cause effects similar to those of stimulants. People trying to improve their focus or energy levels may also misuse diet pills.
Several studies have linked diet pill use and diet pill misuse to eating disorders.
In a study involving more than 1,300 people with eating disorders, researchers found several factors associated with diet pill use:
The study was published the journal Eating Behaviors in 2008. Diet pill use was not associated with excessive exercise, major depression or narcissistic personality disorder. That means people with different types of eating disorders may be more likely to use diet pills.
According to the study, these eating disorders were associated with diet pill use:
The restricting subtype of anorexia nervosa was not associated with diet pill use. The study did not develop conclusions for other subtypes of eating disorders.
In general, FDA-approved diet pills are considered safe and effective when used alongside diet and exercise plans. If those plans are ignored, the weight-loss pill may not be as effective.
All prescription drugs come with a risk of side effects. Side effects of weight-loss drugs vary depending on the person and the type of medication.
Common short-term side effects of diet pills include:
Diet pills that alter brain chemistry to decrease appetite may cause changes in mood or feelings of anxiety. Weight-loss drugs containing amphetamine may cause dependence or addiction. These pills are approved only for short-term use. Long-term use may increase the risk of addiction.
Lorcaserin, phentermine/extended-release topiramate and orlistat are the only weight-loss medications approved for long-term use. They may be used indefinitely, but the longest studies involving the medications lasted only two years. The risks of lifetime use are unknown.
Misuse of diet pills can complicate existing health conditions. Individuals with eating disorders often experience a range of health issues, including stomach damage, slowed heart rate, low blood pressure, heart problems and brain damage. Diet pills can exacerbate those problems.
Long-term diet pill abuse may lead to addiction. Some diet pills, such as amphetamine-based medications, may lead to physical dependence. Others may cause psychological dependence. Individuals may believe that they must consume diet pills to maintain a certain body weight.
Individuals with behavioral addictions or drug addictions engage in compulsive behaviors despite negative consequences. If someone is physically dependent on a diet pill, they may take it to avoid withdrawal.
Diet pill abuse may be a symptom of an eating disorder. People may take the pills to avoid gaining weight, even if they have dangerously low weight or other health problems.
Warning signs of diet pill addiction include:
Addiction is usually caused by underlying mental health issues, such as a history of trauma or abuse. Other mental illnesses, such as depression, anxiety and personality disorders, often co-occur alongside substance use disorders and eating disorders.
Individuals with an addiction to weight-loss pills should talk to their health provider about the best treatment option. In some cases, a primary care physician may be able to help them stop taking the drug. Inpatient or outpatient eating disorder clinics may also be able to help people address diet pill misuse. Drug rehab facilities may be most appropriate for individuals addicted to alcohol or other drugs in addition to diet pills.