Best of luck to him! I dropped ~100 lbs back in 2013 (from 276 to 170) in the span of about 6 months (in retrospect I approached it a bit too aggressively lol), it certainly wasn't easy but once you get into the rhythm of eating healthy and working out regularly it really becomes your lifestyle, I'm now a long distance runner and generally very active. I can say from experience it is absolutely amazing being in shape and you really don't realize how crappy you feel when you're obese since you're so used to it.