For most men, hair loss is caused by miniaturization. This process occurs when hair follicles are triggered – by dihydrotestosterone (DHT) – to grow for shorter and shorter periods, making the hair very weak and small. For now, there is no way to keep miniaturization from starting. "The only preventative measure that a guy can take is early intervention," says Kobren.
There are, however, quite a few things a man can do to address balding once it has begun, like medications and surgery. And with medication, some men can turn the hair clock back as much as five years.