Introduction to Weight Loss Medications

Feb 09, 2022

As an obesity medicine physician, I prescribe medications to some of my patients to help them lose weight.  While these medications are not a “magic pill,” for some they can be helpful when combined with nutrition, physical activity, and behavioral changes.  When choosing a medication, I consider the root cause for weight gain in each patient, and how specific medications can help with hunger, cravings, and insulin resistance.

Your doctor might prescribe a weight loss medication for you if you are having a hard time losing weight or keeping it off with life-style changes and:

  •  Your body mass index (BMI) is greater than 30, or
  •  Your BMI is greater than 27 and you have a serious medical problem related to obesity such as diabetes or high blood pressure.

There are many prescription medications available and they work in different ways.  Below are some of the FDA-approved weight loss medications:

Phentermine (Adipex, Lomaira) is a stimulant medication that has been around since the 1950s and is a controlled substance that is approved for short term use by the FDA.  It decreases hunger in the part of the brain that regulates appetite called the hypothalamus and can also increase metabolism slightly.  Main side effects include some trouble falling asleep (especially for the first few days), dry mouth, and constipation.  This should be avoided by anyone with active cardiovascular disease, glaucoma, or hyperthyroidism. 

Orlistat (Xenical, alli) is a medication that works by blocking fat absorption.  Because of this, the main side effects include cramping, malabsorption of fat-soluble vitamins, and oily spotting. This is a medication that should be used in conjunction with a low-fat diet and a daily multivitamin.

Phentermine and Topiramate ER (Qsymia) is a combination that is more effective than either alone due to their synergistic effect that leads to a decrease in hunger and cravings.  Qsymia can have side effects of both phentermine and topiramate.  Use of this drug requires regular pregnancy testing because of the potential for birth defects.  It should also be avoided by anyone with a history of kidney stones, heart disease, and glaucoma.  

Naltrexone HCl and Bupropion HCl (CONTRAVE®) is useful for curbing excessive hunger and cravings and is tapered up slowly to minimize side effects.  Common side effects include nausea, constipation, headaches, dry mouth, and a temporary increase in blood pressure.  It should be avoided if you have a history of seizures, untreated high blood pressure, or bulimia.

Liraglutide (Saxenda) is an injection that can help with those with insulin resistance and hunger.  Some side effects include nausea and abdominal discomfort, and rarely pancreatitis.  It should be avoided if you have a family history or personal history of medullary thyroid cancer or MEN-2A/B.

Some additional “off label” medications that can be used for weight include but are not limited to:

Metformin is helpful in those with insulin resistance including PCOS, prediabetes, and diabetes.  Common side effects include gastrointestinal symptoms that can be minimized by dose and formulation of the medication. You should use caution if you have a history of kidney disease and watch your B12 levels.

Topiramate is a medication traditionally used for seizures and migraines.  However, it has been found to minimize cravings in some.  It should be avoided if you have a history of kidney stones and by anyone pregnant or trying to get pregnant.  It can cause sleepiness and taste changes. 

Everyone has different reasons for hunger and weight gain. Some people are very hungry while others are not hungry at all but seem to have lots of urges and may buffer or stress eat.  In addition, medications, stress, poor sleep, or insulin resistance can make it hard to lose weight.  Knowing your eating patterns and underlying medical conditions can help to decide if and what medication may be right for you. 

If your doctor starts you on a medication to help with weight loss, you need regular follow up appointments to watch for side effects and to determine if you are getting the desired weight loss.  Medication can be part of a weight loss program for some but should not be used alone without lifestyle changes.  Also, if you are pregnant or planning pregnancy you need to discuss this with your doctor.  None of the FDA approved medications are safe during pregnancy, and Topiramate is known to cause birth defects.

In future blogs I will detail the benefits and side effects of individual medications, as well as discuss other non-medication approaches for lowering appetite and addressing insulin resistance. I hope you found this overview helpful! 



DISCLAIMER: Sarah Smith MD is a medical doctor, but she is not your doctor, and she is not offering medical advice on this website. If you are in need of professional advice or medical care, you must seek out the services of your own doctor or health care professional.