Betmiga shouldn’t cause any weight gain. In fact, a small study with 12 participants found that mirabegron, the active ingredient in Betmiga, increased their ability to burn calories by an average of around 200 calories. It's important to note, however, that this study involved only male participants who were given a higher dose of mirabegron (200mg) than the usual therapeutic dose (50mg).[popover id=ref7]