💊 What a strange phenomenon... this epilepsy medication causes weight loss

Scientists from Laval University and the University of Texas Southwestern Medical Center have joined forces to understand through what strange mechanism topiramate, a molecule initially approved for epilepsy treatment, manages to cause weight loss.

The results of their work, just published in the journal Obesity, reveal among other things that this molecule's mode of action differs from that of the appetite-suppressing molecule contained in Ozempic and Wegovy.


Topiramate is an anticonvulsant that was approved in the United States in 1996 for epilepsy treatment. Over the years, benefits have been discovered for other health problems such as migraines, bipolar disorder, and alcoholism.

"It was by observing weight loss in some people who were taking topiramate to treat epilepsy that its use in obesity treatment was considered," recalls Natalie Jane Michael, professor at the Faculty of Pharmacy at Laval University and researcher at the Research Center of the University Institute of Cardiology and Pneumology of Quebec-Laval University.

In 2012, an American company marketed an obesity medication that combines topiramate and phentermine. This medication, called Qsymia, is now sold in the United States, South Korea, Sweden, Norway, Poland, Denmark, Iceland, Finland, and the United Arab Emirates. "Even though it has been used to treat obesity for more than a decade, we still didn't know its mode of action in the brain," emphasizes Natalie Jane Michael.

To answer this question, Professor Michael and her collaborators used an electrophysiology technique that allows direct measurement of neuronal electrical activity in the brains of transgenic mice. "We discovered that topiramate inhibits a population of neurons (NPY/AgRP) well known for triggering appetite. Unlike other appetite-suppressing molecules like semaglutide (Ozempic) or liraglutide (Saxsenda), topiramate does not act on the neurons that regulate the feeling of fullness."

People who take Qsymia lose on average 10% of their weight. "The results are very variable, however, notes Professor Michael. In some people, weight loss is negligible, while in others it can reach 20% of body weight. It depends on personal genetic background and individual response to food intake. This variability is also observed with Ozempic. It happens that some people gain weight when taking this medication. Better understanding the mode of action of appetite-suppressing molecules could help better personalize treatments and optimize their benefits for people living with obesity."

The study published in the journal Obesity is authored by Moein Minbashi Moeini, Olivier Lavoie, Alexandre Caron and Natalie Jane Michael from Laval University, and Kevin Williams from the University of Texas Southwestern Medical Center.