How Does Topamax Help Weight Loss?

Topamax—also known as topiramate—was originally given FDA approval for the treatment of epilepsy. During clinical trials of Topamax, one of the most common side effects was significant weight loss. Topiramate has never received FDA approval for the treatment of weight loss, and all weight-loss treatment is off-label. According to the American Diabetes Association, when Ortho-McNeil was conducting clinical weight-loss trials, there were too many adverse effects associated with using the drug in this manner, so clinical trials were discontinued. Physicians are aware of the off-label uses of Topamax, however, and many prescribe it to patients as a weight-loss aid.

Weight loss was one of the most common side effects of Topamax, occurring in between 11 and 26 percent of patients taking the drug. According to Ortho-McNeil's Topamax website, some patients lose weight while taking Topamax, and the amount of weight loss varies according to the dosage taken. On his Bellaire Neurology website, Dr. Brian Loftus states that some patients lose as much as 15 to 20 percent of their body weight while taking between 100 and 200 mg Topamax, and they report that the weight loss is effortless.

The specific mechanism of weight loss resulting from topiramate is unknown; however, there are some common theories about how Topamax helps to facilitate weight loss. According to the Topamax website, one side effect of the drug is changes in the sensation of taste due to a reduction of saliva. In some patients, this change in taste may be so severe that they lose the pleasure associated with food, which may lead to weight loss.

The American Diabetes Association reports other theories as well. One theory suggests that Topamax may reduce leptin present in cortisol. Cortisol is a stress hormone that leads to increased insulin production. Melissa Conrad Stoppler, MD, explains that this can lead to increased appetite and cravings, and that cortisol can have a significant impact on weight gain or preventing weight loss.

Another theory supported by the American Diabetes Association discusses how Topamax may act on blood glucose and insulin secretion, which can lead to weight loss through ketosis. This is similar to how weight is lost on low-carbohydrate diets, which rely on the body's fat stores as their primary source of fuel, as opposed to relying on food sources of energy. Yet another theory supported by CNN's Dr. Sanjay Gupta suggests that Topamax may act on the addiction centers of the brain, causing little or no desire for addictive substances like alcohol, tobacco or food.