S.
Your son needs help. You know this. If he can devour a whole bag of apples just to eat? He needs help.
You will have to change EVERYTHING in the house for this problem. That means EVERYONE needs to eat the same things - stop hiding the food. Your son has a problem and he is using food to fill that space or cover up whatever it is that is bothering him.
You MUST acknowledge this and get him to a psychiatrist and get him help. This isn't going to be a one visit and done thing - this is going to be a long-term process to help him work through whatever is making him turn to food for help.
It doesn't matter if you buy a Total Gym or a tread mill - if he doesn't use it - it will just collect dust. Period. End of story.
Has this doctor run any blood tests on your son? Cholesterol, blood sugar, any thing and everything to find out if he's deficient in something?
Begging, pleading, using bribe's isn't going to work. the whole family needs to be on the healthy eating.
Was the doctor rude? Maybe. He doesn't have bedside manners, that much is true. You've been seeing him for 7 years. He has probably been telling you there is problem and you haven't listened or you have made excuses, so he said something that finally got through to you. You didn't like it. Now what are you going to do about it? He told you the truth.
I have a 15 year old, he got chunky as he entered puberty. He's now taller than me at 5' 10". I think he's going to be tall like his dad. Is it possible your son is still going through puberty? I don't think so, as much as I'd like to say here's the reason for your son's weight problem. I would stop hiding food and start addressing the problem, which isn't the doctor, but whatever is bothering your son to have him use food as a crutch.