Agree with you, however at this stage he isn’t even having 3 proper meals each day or having a little of each of the food groups.
We eat very healthy, junk food entails maybe once every 6 month or so.
Even our once a week take out is grilled fish and salad and no sweets or junk food in our home as we are just not into it.
We're all a sample size of one.
Unless you’re worried an eating disorder is at play, I think it’s best to keep offering foods and modeling good eating habits. Take him for a check up. If all his bloodwork is good. Don’t worry. If the doctor is concerned about his low weight and his activity level probably best to let the GP have that chat with him directly. He might hear it more from someone else.
It’s incredible how the conversation in nostr is more civilize