Medications can have effects beyond their primary purpose. One unintended consequence is a change in body weight. While some drugs are prescribed for weight management, others may cause weight loss as an unexpected side effect. Understanding which medications cause such changes is helpful for individuals and healthcare providers.
Drug Classes Associated with Weight Loss
Several medication categories can cause weight loss as a side effect. Stimulant medications, often prescribed for conditions like attention-deficit/hyperactivity disorder (ADHD), can reduce appetite and increase energy expenditure. Examples include phentermine, sometimes used as a short-term weight loss aid, and other amphetamine-related compounds.
Hormone-related medications can also influence body weight. Thyroid hormones, such as levothyroxine, are used to treat an underactive thyroid. If the dosage is too high, it can accelerate metabolism and lead to unintended weight loss. Some diabetes medications are particularly notable for their weight-reducing effects.
Glucagon-like peptide-1 (GLP-1) receptor agonists, including semaglutide (Wegovy, Ozempic) and liraglutide (Saxenda), were initially developed for type 2 diabetes but are now also approved for chronic weight management. Another class, sodium-glucose co-transporter 2 (SGLT2) inhibitors, such as empagliflozin, also used for type 2 diabetes, promote weight loss by increasing glucose excretion in urine. Metformin, a common first-line diabetes medication, is also associated with modest weight loss.
Certain psychiatric and neurological medications can influence weight. The antidepressant bupropion (Wellbutrin) often causes weight loss, unlike some other antidepressants. Topiramate, an anticonvulsant medication used for seizures and migraine prevention, often leads to weight loss.
Specific treatments for other conditions may also result in weight reduction. Some antiretroviral therapies used to manage HIV can cause unintended weight loss, sometimes due to effects on appetite or nutrient absorption. Chemotherapy drugs often lead to weight loss due to side effects like nausea, vomiting, mouth sores, and altered taste, making eating difficult.
Mechanisms Behind Drug-Induced Weight Loss
Medications cause weight loss through diverse physiological pathways. Appetite suppression is a common mechanism, where drugs influence brain signals that regulate hunger and satiety. Stimulants, GLP-1 agonists, and bupropion can decrease cravings and make individuals feel full more quickly. Topiramate also contributes to weight loss by altering appetite and enhancing feelings of fullness.
Some medications can increase the body’s metabolic rate. Bupropion, for instance, may increase energy expenditure. Topiramate has also been suggested to potentially increase energy expenditure.
Malabsorption of nutrients is another mechanism. Orlistat, a lipase inhibitor, works by blocking the enzymes that break down dietary fats in the digestive system. This prevents about a third of ingested fat from being absorbed, leading to its excretion and weight loss.
Increased fluid excretion can also contribute to weight reduction. SGLT2 inhibitors, for example, cause the kidneys to excrete more glucose and sodium through urine, which results in fluid loss and a decrease in body weight.
Many drugs induce weight loss indirectly by causing gastrointestinal side effects like nausea, vomiting, or diarrhea. These symptoms reduce a person’s desire or ability to eat, leading to decreased food intake and weight loss. This is commonly observed with GLP-1 agonists and chemotherapy drugs. Some medications may also influence fat storage and breakdown. Topiramate, for instance, has been shown to affect lipid metabolism and may reduce fat gain.
Important Considerations for Patients
Unintended weight loss while taking medication can be concerning. Never stop a prescribed medication without first consulting a healthcare provider, even if weight changes are observed. Abruptly discontinuing medication can lead to adverse health outcomes or worsen the condition being treated.
Patients should seek medical advice if they experience significant or rapid weight loss, especially if accompanied by other symptoms such as fatigue, dizziness, or changes in energy levels. These symptoms could indicate that the medication dosage needs adjustment or that there is an underlying issue requiring attention. Open communication with a doctor is important to evaluate the situation.
It is helpful to monitor body weight and any accompanying symptoms consistently. Maintaining a record of weight fluctuations and other physical changes can provide valuable information for the healthcare provider. This allows for a more informed discussion about the medication’s effects and potential next steps.
A healthcare provider can help determine if the weight loss is an expected part of the medication’s action, as is the case with some drugs also used for weight management, or an unwanted side effect. They can discuss potential adjustments to the medication, explore alternative treatments, or recommend dietary changes to manage weight. Working collaboratively with the healthcare team ensures that medication use is safe and effective for overall health.