Prescription Weight Loss Drugs
Obesity is a chronic condition that affects about 42% of U.S. adults.1 Approximately two-thirds of U.S. adults are either overweight or have obesity.2 Obesity is associated with nearly 200 medical conditions.3 It raises your risk of developing serious diseases, reduces your quality of life, and shortens your life span.
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People used to think that counting calories eaten and burned and eating at a calorie deficit would lead to steady weight loss (the 3500 kcal per pound rule). We know now that attempts to lose weight are countered by protective mechanisms in the brain that help your body hold on to calories as you try to lose weight.4 Adult body weight is remarkably stable, which leads most scientists to agree that your body works hard to regulate your appetite and hunger to control your weight.5
Obesity, as a chronic disease, is underdiagnosed and undertreated. There are prescription and non-prescription treatment options for treating obesity. All weight-loss medications have side effects; some are serious, but having obesity also has serious health ramifications.
Common Prescription Weight Loss Drugs
In the last decade, newer and more effective weight-loss medications have become available. In 2013, the American Medical Association designated obesity as a disease, opening the door for increased funding for obesity research and medication development.6
Commonly prescribed weight loss medications include:
- Phentermine: A stimulant medication that is FDA-approved for short-term use, phentermine is an adrenergic agonist that suppresses appetite. It should be used with caution in people with high blood pressure and should not be used by people with hyperthyroidism, glaucoma, severe anxiety, or other mental health conditions.7
- Orlistat: Unlike other weight-loss medications, orlistat is a selective pancreatic lipase inhibitor that blocks fat absorption by about one-third. It limits the amount of dietary fat your intestines absorb. It causes reduced absorption of fat-soluble vitamins, excess gas, and loose stools.8
- Phentermine/topiramate: Combines an adrenergic agonist or stimulant (phentermine) and anti-seizure medication (topiramate) and provides additional benefits for people with obesity and migraines. These medications combined have greater weight loss effects and fewer side effects than either alone.9 They should not be used in people with uncontrolled high blood pressure, coronary artery disease, hyperthyroidism, glaucoma, or sensitivity to stimulants. The combination may lead to congenital anomalies (birth defects) and should not be used by anyone who is pregnant or planning to become pregnant.
- Bupropion/Naltrexone: Combines a dopamine/norepinephrine reuptake inhibitor or antidepressant (bupropion) and an opioid receptor antagonist (naltrexone). It helps people resist cravings and food addictions. Do not use if you have uncontrolled high blood pressure, seizures, a history of eating disorders, or are withdrawing from drugs or alcohol.
- Liraglutide: A glucagon-like peptide 1 (GLP-1) receptor mimetic that is used to treat type 2 diabetes and for weight loss. By delaying stomach emptying, liraglutide helps you feel full longer. It may increase the risk of pancreatitis.
- Semaglutide: Like liraglutide, semaglutide is a glucagon-like peptide 1 (GLP-1) receptor mimetic that is used to treat type 2 diabetes and for weight loss. Semaglutide also delays stomach emptying and suppresses hunger. It may increase the risk of pancreatitis.
Obesity, like all chronic diseases, needs long-term treatment. As long as the medication benefits outweigh the potential side effects, patients with obesity should continue to receive anti-obesity treatment.
What Do Prescription Weight Loss Pills Treat?
Weight loss medications treat obesity. They can also be prescribed for people who are overweight and have an obesity-related medical condition. These medications are intended to support weight loss efforts, along with a healthy diet and exercise. Weight loss can also reduce blood sugar spikes and type 2 diabetes risk, lower blood pressure, and improve triglyceride and cholesterol levels.
How Do Doctors Determine When To Prescribe Weight Loss Medication?
Prescription weight loss medications are prescribed for people with obesity, which is defined as having a body mass index (BMI) of 30 kg/m2 or higher, or people with a BMI of 27 kg/m2 or higher who also have a co-existing serious medical condition that is related to obesity. Examples of obesity-related medical problems include type 2 diabetes and high blood pressure.
The U.S. Preventive Services Task Force (USPSTF) and the National Institute for Health and Care Excellence (NICE) recommend screening all adults for obesity. Up to 90% of people with obesity have not received a formal diagnosis.10
In a study that involved nearly 15,000 patients with obesity and 2,785 primary care healthcare providers, researchers found that there was an average of six years between when a patient developed obesity and when their healthcare provider discussed it with them. This study illustrates the importance of taking a proactive role in weight management. If you are concerned about your weight, discuss your concerns with your doctor. Many healthcare providers are uncomfortable discussing weight and obesity with their patients.11
Do Weight Loss Pills Work?
Clinical trial results and combined analysis of research studies using weight loss medications in multiple populations provide data on how effectively these medications work and the expected weight loss you can achieve. Even a 5% weight loss can improve your health.
- Phentermine: A stimulant medication that is FDA-approved for short-term use, phentermine is an adrenergic agonist that suppresses appetite. Average weight loss is about 3% of your initial body weight after three months and 5% to 7% after six months, or about 8 pounds over what is expected with diet and exercise alone.12
- Orlistat: Taking the prescription or over-the-counter forms of orlistat produces an average weight loss of about 6.5 to 7.5 pounds (3.0 kg) in a year.12
- Phentermine/topiramate: The average expected weight loss for patients taking this combination is about 14.5 to 19 pounds (9.8 kg) in one year.8,12
- Bupropion/Naltrexone: The average expected weight loss is about 4.4 kg in one year.8
- Liraglutide: A meta-analysis of research studies found that patients taking liraglutide achieved an average of 5.25 kg weight loss in one year.8
- Semaglutide: In clinical trials, patients attained a 15% to 18% weight loss over 68 weeks. In a study that enrolled nearly 2,000 participants, people taking semaglutide lost an average of 34 pounds (15.3 kg) compared to 5 pounds (2.6 kg) in the control group.13
All injectable weight loss medications are prescription only. Weight-loss medications and devices will not work for everyone and can cause harm if people with certain medical conditions use them. If you have not lost weight after taking a prescription weight-loss medication for 12 weeks, talk to your doctor to see if you need a new prescription medication or dosage.
The high price tag for many prescription weight loss medications and the lack of insurance coverage can tempt many people to seek these medications from online stores that do not require a prescription. However, these unregulated medications are not safe and may contain dangerous ingredients such as ephedra, which the FDA banned in 2004 because of its potentially dangerous side effects. Prescription coverage is expected to improve if people achieve significant weight loss and reduce their risk for chronic diseases after taking anti-obesity medications.
Prescription Weight Loss Drugs Don’t Replace Physical Activity
Prescription weight-loss medications are important tools to help you lose weight, but consuming a healthy diet and engaging in regular exercise are also important. Exercise helps you retain and build muscle mass as you lose fat mass. As you lose weight, your resting metabolic rate decreases because you have less weight to carry around. Increased muscle mass can help counteract this effect.14 Exercise also improves your cardiovascular fitness, which can mean more energy and a healthier lifespan.
Many people find exercising for weight loss frustrating because the expected weight loss based on calories burned is significantly more than most people experience. When trying to lose weight, it is almost impossible to counteract the effects of a high-calorie diet with exercise alone. An exercise-induced appetite increase may be responsible for slow weight loss, or decreased physical activity when not exercising may contribute to slower-than-expected weight loss.
The Centers for Disease Control and Prevention and other societies recommend 150 minutes of moderate-intensity exercise or 75 minutes of intense exercise each week, along with at least two weekly strengthening sessions that target all major muscle groups.
The U.S. Department of Health and Human Services and the American College of Sports Medicine (ACSM) recommend increasing your exercise to at least 300 minutes per week of moderate-intensity exercise to lose or maintain weight. Try to increase your exercise intensity to vigorous, especially if you have a tight schedule.
While dietary choices are more likely to have a bigger effect on your weight loss, exercise has many benefits. Try some of these:
- Walking: walk on an incline or carrying weights for added calorie burn
- Jogging or running: faster movements, especially on an incline, can burn about 100 calories more than walking for each 30-minute session, according to Harvard Health
- Cycling: is a great, low-impact, aerobic workout
- Swimming: exercises most major muscle groups in a low-impact environment
- Stretching and yoga: increases strength and flexibility
- Leisure activities: golf, bowling, skiing, and boating are all great outdoor activities that increase calorie burn
- Competitive sports: basketball, tennis, volleyball, and racquetball can make exercise fun
- Outdoor activities: hiking, rock climbing, and other outdoor activities can relieve stress, which can also help with weight loss
If you have a medical condition that exercise can exacerbate, check with your doctor before starting an exercise program. Otherwise, choose any activity you enjoy and set a goal. No matter how big or small, once you incorporate physical activity into your daily schedule, you will reap the benefits of better health and weight management.
More Weight Loss Tips
Body composition is the percentage of body fat and lean muscle mass that make up your total body mass. Many people, especially athletes, have high muscle mass and, therefore, higher BMIs. A better sign of your weight loss progress is measuring your waist circumference or checking how your clothes fit. Take pictures throughout your weight loss journey. Don’t use the scale as your single measure of success.
Work on increasing muscle mass, reducing fat mass, and getting stronger and healthier. Unfortunately, hormonal changes can make achieving these goals more difficult as we age. For this reason, many people turn to supplements to restore nutrient deficiencies and support their weight loss efforts.
While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.
1. The Organization for Economic Co-operation and Development. Obesity Update 2017. Accessed August 13, 2022. https://www.oecd.org/health/health-systems/Obesity-Update-2017.pdf
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