Hi! I believe I can be of help with this issue.
I can imagine how frustrating this situation must be for you. You are clearly loving and caring mom. He's fortunate to have you making these efforts on behalf.
I can understand why the doctor says it can't be the Concerta. Concerta is recognized to be an appetite suppressant. Now, with every drug there are going to be those rare exceptions who have the opposite reaction to the drug. But let's assume your son is not that one in a million because that won't help much: if the Concerta is helping him with the ADHD symptoms, then the loss is greater than the benefit of discontinuing the medication. Because the chances are so slim that he's that rare exception.
Now, that said, I have heard of kids gaining weight while on Concerta. And this is the scenario: the appetite suppressing effect keeps the kid from eating during the day. Then in the evening when the med wears off, he gets very hungry and eats too many calories in one sedentary period. This gets managed by limiting availability of the kitchen in the evening.
So, this needs to be explored, if the timing of his eating needs to be worked on so that he's not overeating and undereating in sequence during the day.
If this is not a problem, or even if it is, it sounds as though you are going to need to use some behavior modification techniques with him. 13 year olds are already very reward conscious. You might need to have a weigh in ever day at the same time and have a weekly reward and a monthly reward for consistent weight loss.
The same might be done for making healthy food choices as opposed to junk food. Or incorporate the two reward systems. In one sense, I imagine he is used to having charts around because of ADHD, so this will be a familiar one with rewards involved.
Next, you might have to have the football coach in on this. If he is health conscious, that would make it easier to enlist his help in getting your son on a healthy diet regime. The more you can have people who he wants to please and impress get him to make the behavior changes, the less you have to nag him and that's always a plus.
Okay, I wish you the very best!
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