.LittleThings / Maya Borenstein
Though weight gain can be caused by many factors, suddenly weight gain without any changes to your dietary or physical habits could be cause for concern, according to WebMD.
In fact, it’s one of the main reasons people show up in Dr. Miller’s office. “They’ll tell me that they aren’t eating any more than usual, but they’re gaining weight,” she says. “They are exercising, but they are getting nowhere. They can’t lose it.” It’s almost always due to an under-active thyroid, she says.