Medications that promote weight loss

Picture of Dr. Jen Kerns

Dr. Jen Kerns

If you take any medications at all, be sure to check out my blog from 2 weeks ago about meds that can make you gain weight.

On the flip side, certain medications can actually help you lose weight. (Before trying any of these medications, be sure to discuss with your own healthcare provider and be sure that you don’t have any contraindications to their use!) The obvious ones are medications that are already FDA-approved for the indication of treating obesity:

1. Orlistat (trade names Xenical and Alli): this is the only FDA-approved anti-obesity medication available over the counter. It works by blocking digestive enzymes that break down fat, thereby causing about 1/3 of the fat you eat to be lost with your stool. Warning: if you take this medicine with a high fat meal, you will block a lot of fat, and too much fat in the stool causes diarrhea or even oily leaks if bad enough! (Taking it with a relatively low fat meal will usually just cause a change in the consistency of the stool, but not frank diarrhea.) Fat soluble vitamins (like D, E, A, and K) can also be lost, so multivitamin and vitamin D supplements should be taken at a time separate from the medicine. People on orlistat lose on average about 4% more weight than people on a placebo do after a year.

2. Phentermine + topiramate (trade name Qsymia): this one is a controlled substance due to the phentermine component, which is an addictive stimulant similar to amphetamine. The combo pill has a relatively low dose of phentermine, which raises the sympathetic nervous system (and can raise blood pressure and heart rate) and suppresses appetite. The extended-release topiramate component is thought to increase the sense of satiety after eating and can adversely affect the taste of certain foods, making them less appetizing. Notably, topiramate causes birth defects, so any woman of child-bearing age will have to use two forms of birth control and get monthly pregnancy tests in order to use this medicine. People on the high dose of Qsymia lose on average 9.8% more of their weight than do people on placebo after one year.

3. Naltrexone + bupropion (trade name Contrave): this combines an endorphin-blocker (naltrexone), which is thought to decrease the reward signals in the brain that respond to food (and thereby affect cravings), with an antidepressant (bupropion) with stimulant effects that has been shown to suppress appetite and increase energy expenditure. Heart rate and blood pressure must be monitored to ensure they remain controlled, and the drug can’t be used in people who take opioid pain medicines or who abuse opiates (like heroin). The antidepressant component can lower the threshold for seizures, and there’s a black box warning about suicide risk which is required of all antidepressants (even though Contrave is not approved for the treatment of depression). People on Contrave lose about 4-5% more weight than people on placebo after one year.

4. Liraglutide (trade name Saxenda): this drug is thought to work by slowing down the time it takes the stomach to empty, which leads to feeling full more quickly, and by suppressing appetite in the brain. The downside of this one is that it is a daily injection rather than a pill. It has the added benefit of improving blood sugar in people with type 2 diabetes (and having a decent rate of reversing prediabetes in people with borderline numbers), and an industry-sponsored study published in the New England Journal of Medicine in 2016 found a benefit in delaying heart attack and stroke and decreasing death from cardiovascular causes in people with type 2 diabetes who took liraglutide vs. placebo. People on Saxenda lose about 4% more than do people on placebo after a year. (Other drugs in the same class such as semaglutide/Rybelsus/Ozempic and dulaglutide/Trulicity also likely have the same weight loss effect, but have not been officially studied and approved for use to treat obesity.)

5. Gelesis100 (trade name Plenity) has been approved by the FDA but has not been manufactured enough to actually be available for use yet! It is actually classified as a medical device rather than a medication because it’s a unique hydrogel that expands in the stomach by absorbing water and expanding to take up space there (thereby limiting subsequent caloric intake) but is not absorbed into the body. Plenity helps people lose about 2% more than placebo over 6 months.

6. Phentermine (under countless trade names): this is the same stimulant that is used in Qsymia, and again, as an amphetamine-like drug, it is addictive and a usable, so it’s a controlled substance. It’s only supposed to be used for up to 12 weeks at a time, and can raise blood pressure and heart rate similar to other stimulants. (And other stimulants like methylphenidate/Ritalin and amphetamine+dextroamphetamine/Adderall may have similar effects on appetite, energy expenditure, and weight.)


Other medications can also help promote weight loss even if they aren’t specifically approved by the FDA for that indication, and a few are commonly prescribed by obesity medicine specialists off label:

7. Metformin (trade name Glucophage): this drug is widely used off label by obesity medicine specialists (myself included) to help promote weight loss after being shown to do so in a pivotal clinical trial called the Diabetes Prevention Program. It was also shown to decrease the risk of people with prediabetes progressing to full blown type 2 diabetes, so may be of particular benefit in people with higher blood sugars. Also notably, Metformin has been shown to reduce all-cause mortality in multiple different clinical trials, so it’s a hot prescription among the biohackers in Silicon Valley who are trying to prevent cancer and increase longevity (despite no actual clinical evidence that it does this in otherwise healthy humans)!

8. Topiramate (trade name Topamax): this drug is one of the two drugs in Qsymia (above), and is used off label for weight loss and also seems to help quell binging and purging behaviors in people with binge eating disorder and bulimia. It’s also preferred for weight regain after bariatric surgery.

9. Naltrexone (trade name Vivitrol or ReVia): a component of Contrave (above), this medicine is sometimes used off label to help with cravings and food addiction.


While lifestyle changes alone are often sufficient to achieve a meaningful weight loss, the addition of medication can often be helpful. However, any weight loss attributed to a medicine will likely be regained if the medicine is stopped, and weight loss medicines are not effective without concomitant changes in diet and activity. Not all primary care providers are comfortable prescribing medicines for weight loss, so physicians certified by the American Board of Obesity Medicine can be a great resource if you need extra help.




Leave a Reply

Your email address will not be published. Required fields are marked *