What to Know About Weight Loss Medications

Posted: September 9, 2020 in Pharmacology by
Appetite Suppressant Weight Loss Medications

There are a lot of misconceptions out there about weight loss medications. In this post, I cover common questions my patients ask me about obesity medications and appetite suppressants.

Should I take a weight loss medication? If so, which one is best?

The answers are both straightforward and ambiguous. Anti-obesity medications are FDA approved for patients who have a BMI over 30 and for patients who have a BMI over 27 if they also have a weight-related medical condition, like high blood pressure, high cholesterol, type 2 diabetes mellitus, or sleep apnea. I also use the medication if a patient has obesity based on body fat percentage, which is generally accepted to be >32% for women and >25% for men.

When is it okay to go on weight loss medication?

Most of my patients have tried to lose weight on their own many times before they come to see me. In the past, they have struggled with hunger and cravings, and untreated, it has usually been the primary reason they didn’t succeed in losing weight or keeping weight off. As one of my mentors always says, “It’s not willpower, it’s physiology”. We know that as soon as a person starts losing weight, their body fights against weight loss by altering hunger hormone levels to increase hunger and slow metabolism. These hormones don’t just change for a brief period of time to try to stop the weight loss, it looks like these changes persist for years afterward.

Abnormal physiology in the brain drives inappropriate hunger and cravings and slows metabolism. In simplified terms, anti-obesity medications act at the hormone and brain level to decrease this inappropriate hunger. If a patient is struggling with hunger or cravings, I use medication to control the symptoms. The other reason I use medication is when a patient’s weight loss is less than what I expect it to be.

What are the types of weight loss medications?

There are now several medications that are FDA approved to treat weight. I frequently use four of them and will focus on those. Another one, Orlistat, commonly causes undesirable gastrointestinal side effects, so I avoid it unless a patient specifically asks for it.

  • Phentermine is what most people commonly think of as an appetite suppressant. It was FDA approved in 1959 and works primarily to increase levels of the hormone norepinephrine. Phentermine is available generically and is the least expensive at around $25 per month.   It is and has been the most used anti-obesity medication for over fifty years.   
  • Qsymia is a combination of phentermine and topiramate that was FDA approved in 2012. While phentermine mostly acts to increase norepinephrine levels, the exact mechanism of action of topiramate for weight loss is not fully understood, it is thought to be through an increase in GABA, a neurotransmitter.  The cost of Qsymia varies depending on insurance coverage and if it is prescribed in the brand name form or as the two generic medications.
  • Contrave is a newer generation medication that was FDA approved in 2014. It’s actually a combination of two older medications, bupropion, and naltrexone. It acts in the brain by increasing levels of the hormones dopamine and norepinephrine. It works on the appetite center but stands out by also working on the craving centers of the brain.  Cravings are those very specific tastes for particular foods that may occur at times of the day even when you may not feel particularly hungry.    
  • Saxenda is also a newer generation medication that was FDA approved in 2014. Saxenda is a daily subcutaneous injection that acts on a receptor for a hormone called Glucagon-Like-Peptide 1 (GLP-1) in the brain to decrease hunger. In its natural form, GLP-1 comes from the small intestine and goes in the blood to the brain to signal fullness. It usually breaks down in about 2 minutes, Saxenda the modified form, lasts about 13 hours.   

How much do weight loss medications cost?

The cost of the medications varies widely depending on insurance coverage. All of the medications reduce hunger and cravings, and they should always be used in combination with nutrition, physical activity, and behavioral changes. None of the medications are recommended during pregnancy. Which medication is best really depends on the individual patient in terms of their medical history and other current medications. To find out which is best for you, talk to your obesity medicine physician or obesity medicine professional.  

Do weight loss medications work?

In terms of how well they work, it’s very difficult to compare them.  No direct head to head studies have been done to compare the medications to each other, and even the data on how well the medications work has been reported differently between studies, again, making it difficult to compare them.

The effect on weight loss of each medication should be evaluated after a specific period of time about three to four months. What works for one person, doesn’t necessarily work for another. There is no one perfect anti-obesity medication.   What medication works for one, will not work for another.   Sometimes, the dosage needs to be adjusted or another medication needs to be added.   In our clinic, we combine anti-obesity medications all the time.   As the treatment of hypertension, where it is common to use two to four anti-hypertensive medications, at times, we will use multiple medications, if needed for effect.  

How long can I stay on weight loss medication?

The FDA approval for phentermine is for 12 weeks of use, however, many obesity medicine physicians prescribe the medication for longer periods of time; this is called off-label prescribing. It is recommended by several publications including the obesity medicine association and AACE publication.   The other anti-obesity medications (including Qsymia, which does contain phentermine) does not have a time limit associated with their FDA approval.

As obesity is a medical disease, like hypertension or diabetes, it is believed that anti-obesity medication should be continued for as long as it is needed and is not causing a problem for the user.  


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