From Roy, Child's Age 17 - 06/17/18 - IP#: 50.89.194.xxx  Click here to reply  
My 17 year old son Benji has gone from a bone thin 5'10 and 160 to 245 pounds in just over a year. Last year (Apr/May 2017), he was on the soccer team and quite athletic with practice and workouts nearly every day. He decided at the end of last year to not continue soccer so he could better his grades in preparation for university.
Fast forward to June of 2018 and he's 245 pounds. I knew he had gained weight, I'm not completely oblivious to the change as gaining 85 pounds in a year is quite a big change to say the least. He outgrew clothes faster (S/28-30 to XL 38-40) than you could ever imagine but he has a job and bought clothes with his own money so I didn't say much of anything.
His appetite has increased but not exponentially so, definitely not enough to gain all this weight just from my food alone. He'll go for seconds at dinner but my food isn't unhealthy - he will load up his plate with vegetables as well as protein/pasta. He (or his brother) will buy junk food and store it in the house. Currently in my pantry there is probably a week's worth of candy/junk if you were to only eat that for 3 meals a day. I've told both of them to stop buying it but it is their money. But, all of my children eat it and when they have friends over they eat it.
His athleticism has reduced to zero. He has a car (well sharing with his twin) so he doesn't need to take the bus. He gets winded just doing the flight of stairs in the house or walking around the mall or supermarket; it's obviously taking a physical toll on him. Looks have changed, went from literally skin, bones and some muscle to gut hanging over shorts, love handles poking out, manboobs increasing in size and face from angular to pudgy - there's no hiding this gain.
He's eating a crap ton outside of the house. He has a car and a job and I can almost guarantee that he's stopping after work (if not before and after) to eat. Include lunch and breakfast.
I'm not sure what to do in this situation. He is the only one who has gained a lot of weight - his twin gained some (maybe 15 pounds) but that's from another scenario that I am well aware of. I can't take his money, he has his own job and he's fiscally responsible (saving, charity, etc.). I'm not going to take his car away because I don't have concrete proof about the after school binging (85 pounds in a year, there must be some binging). I have spoken to him about healthy living and stuff and whenever I bring up his weight he either refuses to talk or shrugs it off.