Honestly, idk because it's not my place. SD10 used to get major cavities, had to have teeth pulled, etc. She would gorge on junk food and not brush teeth before bed. I tried to explain to both DH and SD, but let them find out the hard way with fillings and hundreds of dollars in dental bills later. 

SD10 is very picky and still eats "kiddie food." Spaghettios, chicken nuggets, mac and cheese. She almost always has something different for dinner with the exception of tacos and pasta. 

Personally, I think of myself as a healthy eater. SD is obviously NOT. However, DH doesn't see anything major wrong with it, so I am done trying to "fix it." 

Advice - disengage. Have DH bring it up to the pediatrician next time he's at the doctor if it's a concern of his. 

Get his growth hormones tested. My brother and 2 other people I know of were/are picky eaters that also were diagnosed with lacking growth hormones that required treatment. 

Not all people that are pickty eaters have this issue, but maybe there is some relation? Since he is smaller perhaps it is worth checking? 

 No boys but SD12 (almost 13) is the same way. She has dark circles under her eyes and looks sickly.  She was raised only eating chicken nuggets and fries so that's all she eats...but it will be like one nuggget and the fries.

 no water just soda.....doesnt eat candy or ice cream either. 

at this point I have come to realize that her "picky" eating is for attention....apparently she eats at her moms house but won't eat at ours...if she does eat here the food has to be cut into shapes and arranged on the plate to look like sponge bob (sort of joking) and then DH has to sit with her while she says she doesn't like it....and demands he make something else that doesn't eat. 

i just ignore her and feed my own kids....not my problem.

SS12 is a picky eater but I'm ok with that. We get to save all the good food for us while he eats white bread and noodles. Yay in my book.

Two of my SK were picky eaters, too, and one still is.  I'm kind of laid back so if DH wanted to give them fast food money, whatever.  Does your SS like fast food?  I'd estimate that YSS ate 75% of his dinners at the fast food place.  I originally thought it was a passive aggressive revolt against me and my dinners.  But now I think it was a desire for the consistent taste of fast food.  They weren't adventurous eaters and my "cuisine" must have seemed foreign.

But to be safe, I'd probably agree with the other posters and check with the medical professionals.

have kid tested for any odd genes or hormones. Have him screened for failure to thrive (is that a thing st that age still?)

other than that, let it go. If he stays small, you’ll give him a complex. I had a friend in high school who looked 10 years old almost the whole time. When he turned 17 puberty hit him like a freight train and he ended up looking like a Nordic warrior. 6’1, blonde hair, packed on muscle like it was nothing. 

If it's a true disorder it would manifest early, like my OSD. If so, there's not much you can do now but have your DH understand that now you have to teach a teen how to navigate life with this problem. I have a friend like this and she's aware of it, that it limits where we go out and what we eat together. He can't just refuse to socialize. Do jot cook special meals FOR him, unless your DH does it all on his own. DH did this with OSD for a while before he got sick of it (I also refused to do any clean up associated with a second meal choice) then he made her cook for herself. And if she didn't do it at the right time, then we didn't hold up our meal for her.

We're starting to have issues with YSD14 and picky eating again, she's reverting back to her problems like when she was 9, but I just told DH nope, I'm not catering, you get to cook and figure our what she wants. I'm not going there. With her it's a PAS/power issue I'm sure.

https://health-usnews-com.cdn.ampproject.org/v/s/health.usnews.com/welln...

I thought boys just have the grow spur at a later age? My SS is almost 13 and he's also only near 5ft. We don't really worry that he will stuck at this height though.

my SS is also a picky eater, partially due to being autistic. But DH makes sure he eats well at home (can't do much with school meal or when he's at BM's). It's the bio parents job to make sure their kids eat right imo.

Omg lol I could relate so much to do this. I've started to try to hide veggies in meals for one of my SS. He's 8 and hates veggies. He hates veggies so much that he went back to his BM and told her I "forced" him to eat them! My bf got a call saying to "tell that whore to stop making my son eat veggies if he doesn't want to." Mind you, he's 8 and obese, probably from all the meals she eats out with him instead of cooking. VERY frustrating. I feel like CPS is going to knock on my door and take me away for veggie distribution lol. But stick with it! At the end of the day, you mean well and your concerns are good and well intentioned. Maybe a doctor visit is worth a shot too, esp if he's skipping the sweets too. 

Picky eaters are the result of insecure parents.  Serve what is prepared and they eat... or they don't. If they don't, they can starve until the next meal.  It won't take long for them to stop being picky.

Dont force them to eat. Just don't give them a choice on what they eat.  For most of the history of human existance kids have had to eat what they are served.

It works. Try it.

Is he taking Concerta?  My son lost his appetite when he was on it.  He only had to take it on school days though.

What does his doctor say about his eating? Do you think he might have an eating disorder or just simply a small and picky appetite?

Could it be some form of autism, where he can't stand certain textures? My SD16 and SD18 both have weird eating habits, and I suspect its mental vs. physical. SD16 has problems with textures and SD18 used to only eat white foods - mashed potatoes, bread, white cake, etc. Of course, now SD18 decided she likes meat and white foods, and she will break open the bones and slurp out the bone marrow at the table. Maybe she's a vampire? LOL. But seriously - it could be some form of mental illness/ ocd.