Overweight and obesity have become health concerns worldwide, leading to an increased focus on weight management. Most of the time, the first step toward weight loss is to adopt a healthy diet and exercise more. But these might not be enough. Some people may need extra support. In such cases, weight loss medicines may be prescribed.1
Each weight loss drug works differently. These drugs are prescribed based on a person’s specific needs and medical history. Weight loss drugs should always be taken under the guidance of a healthcare professional. Along with taking drugs, making lifestyle changes such as eating a healthy diet and getting regular exercise has the best results.1
Various types of medicines can be used for weight loss. They include:1,2
Who should consider medicines for weight loss?
Weight loss medicines are typically prescribed for:1,2
- People who have a body mass index (BMI) of 30 or higher, which indicates obesity
- People who have a BMI of 27 or higher along with an obesity-related health condition such as high blood pressure, diabetes, or sleep apnea
Whether a doctor prescribes weight loss medicine also depends on the specific situation, the medicine in question, and local regulations. In general, weight loss drugs may be considered for people who:1,2
- Have been unable to achieve weight loss through diet and exercise alone
- Have a strong motivation to lose weight and are committed to making long-term lifestyle changes
- Are not pregnant or planning to become pregnant, as weight loss drugs may have potential risks for unborn babies
- Do not have other medical conditions that may be affected by the drug (contraindications)
- Are under the guidance of a healthcare professional who can assess their health status, provide proper monitoring, and adjust the treatment plan as needed
Weight loss drugs are not a standalone solution. They are intended to be used as part of a weight management plan. This plan also should include:1
- Lifestyle changes, such as a healthy diet and regular exercise
- Ongoing support from healthcare specialists
How do weight loss drugs work?
Medicines for weight loss work in various ways to help people lose weight. These ways include:1,2
- Reducing appetite
- Promoting the feeling of fullness (satiety)
- Controlling food cravings
- Reducing fat absorption
Medicines that reduce appetite and promote satiety
Some weight loss drugs block the hunger signals from your brain and also help you to feel full.
GLP-1 agonists
GLP-1 (glucagon-like peptide-1) agonists are a class of drugs that were developed to treat type 2 diabetes but also aid in weight loss. These drugs work by stimulating GLP-1 receptors, which regulate appetite and promote fullness.1-3
GLP-1 agonists slow down gastric emptying and therefore reduce food intake. Gastric emptying is the process of food leaving the stomach. In this way, GLP-1 agonists can contribute to weight loss.1-3
Examples of GLP-1 agonists approved for weight management include:1-4
- Liraglutide (Saxenda®)
- Semaglutide (Ozempic®, Wegovy®) – also approved to treat cardiovascular disease in people with obesity or overweight
- Tirzepatide (Mounjaro™)
Anorectics/appetite suppressants
Anorectics act on the central nervous system to reduce hunger and increase feelings of fullness. They are also known as appetite suppressants. Examples of appetite suppressants include:1,2,5
- Phentermine-topiramate (Qsymia®)
- Phentermine (Adipex-P®, Lomaira™)
Medicines that control cravings
Some drugs target the brain’s reward system to help control cravings and reduce food intake. Opioid antagonists are an example.
Opioid antagonists
Opioid antagonists are combination drugs that act on opioid receptors to suppress appetite and increase energy use. They are approved for long-term weight management in people who are obese or overweight and have one weight-related health problem.1
An example of an opioid antagonist is:1
- Bupropion-naltrexone (Contrave®)
Medicines that limit fat absorption
Other weight loss drugs limit the amount of fat that your body can absorb. GI lipase inhibitors are an example.
GI lipase inhibitors
Gastrointestinal (GI) lipase inhibitors block the enzyme lipase. Lipase is responsible for breaking down fats in the gut. By reducing fat absorption, these medicines can lead to weight loss.1,2
Examples include:1,2
- Orlistat (Xenical®, Alli®)
Other weight loss drugs
Other drugs are not approved directly for weight management but may have weight loss as a side effect. These include the following.
Antidepressants
Some antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), are linked with weight loss and weight gain. The 1 antidepressant that has been linked with weight loss to date is:2
- Bupropion (Wellbutrin)
But effects vary, and weight loss may not happen for everyone. Also, antidepressants should only be prescribed for weight management if the person needs them for an underlying mental health condition.2
Anticonvulsants
Some anticonvulsants or antiseizure drugs can cause weight loss as a side effect. The exact way this works is not fully understood. But experts believe that these drugs affect the brain's appetite-regulating centers. Anticonvulsants are primarily prescribed for managing seizures and should not be used only for weight loss.5
Examples of anticonvulsants commonly used for weight loss include:5
- Topiramate (Topamax®)
- Zonisamide (Zonegran®)
Over-the-counter drugs
OTC weight loss drugs are available without a prescription. They can be purchased directly from pharmacies or stores. These products often contain things like caffeine, green tea extract, or fiber supplements. Through these ingredients, they claim to boost metabolism, reduce appetite, or increase fat burning.2
However, the efficacy and safety of OTC weight loss drugs vary. Talk to your doctor before using them.2
Meal replacements
Meal replacement products come in the form of shakes, bars, or prepackaged meals. They provide a convenient and portion-controlled alternative to regular meals. These products often are made to provide balanced nutrition while reducing calorie intake. Examples include:6
- Optifast®
- Medifast
Meal replacement plans are typically designed for short-term use. They are most effective when combined with nutrition counseling and behavioral support.6
For those with rare genetic diseases of obesity
Some people may have a rare genetic disease that causes weight gain. These genetic conditions interfere with certain parts of the brain that affect appetite and regulate hunger signals. People with these conditions have extreme hunger and struggle with focusing on anything other than food. These conditions include:7
- Proopiomelanocortin (POMC) deficiency
- Proprotein convertase subtilisin/kexin type 1 (PCSK1)
- Leptin receptor (LEPR) deficiency
The FDA has approved setmelanotide (Imcivree™) for people who are 6 years of age and older with obesity who have these rare conditions. This prescription drug is a daily injection given under the skin.7
What are the possible side effects?
Like any drug, weight loss drugs can have potential side effects. Side effects can vary depending on the specific drug or treatment you are taking. Here are some potential side effects of different types of weight loss drugs:1-3
- Diarrhea
- Dizziness
- Gas
- Headache
- Increased heart rate and blood pressure
- Insomnia
- Low blood sugar (in people with diabetes)
- Nausea
- Vomiting
These are not all the possible side effects of weight loss medicines. Talk to your doctor about what to expect when taking weight loss medicine. You also should call your doctor if you have any changes that concern you when taking a weight loss drug.
Before beginning treatment for obesity, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.
Talk with your doctor
Medicines for weight loss can be a valuable tool for people who are considered overweight or obese. But weight loss drugs should be used only as part of a comprehensive weight management plan. That includes ongoing monitoring and support to ensure safe and effective results.1,2
Before considering any weight loss drug, ask your doctor about the best option for you based on your specific needs and medical history.