Dick shrinking

Okay, bit of a weird one.

Does anyone know of any guys that have willingly shrank their dick?

I know someone who has but he went too far without realising and regrets it. He saw a doctor and apparently the doctor was shocked and all they could suggest was to exercise it. Now my friends in a pretty dark place right now and this advice really didn’t help him.

Anyone know of a proven way (other than surgery) that he could increase his size again, even just by an inch or so?