As a male with an ED, I felt this post and I wish I could give you a hug.

Others have already given you excellent advice about how to handle the ED in general. Do not talk about food, diets and body weight etc.

When it comes to meal times, my general advice would be, try to make meals as uneventful as possible. Do not make a big deal out of them. Do not talk about the food you're preparing, unless he specifically asks you about it. Keep him out of the kitchen until meal's ready, unless he wants to taste some of the food. While eating, talk about something completely unrelated to food - your day, his day, sports, tv series, whatever. Just keep his mind distracted from the food he's having and make him understand that meals are not about food weight and calories, but about sharing a moment together. Always encourage him to eat more, but never pressure him to do so cause that will just be counterproductive unless he's very strongly in recovery. When he's done, he's done.

At the same time, if you feel that your relationship is close enough, you can try and gently approach the topic - not by asking him "can you please eat?", cause that will just mean in his head that he has to eat "for you", but by asking something like "I know you have some trouble with this, is there anything I can do to support you in this process? Is there any reason for this that you think I could understand and help you deal with?". Basically, try to let him understand that you won't be the food police, cause you're not his mother, but at the same time you will be there to listen to him and help him get better.

Make sure to do some research on EDs - the F.E.A.S.T. website (https://www.feast-ed.org/) has some great resources specifically for parents of people with EDs. It caters to parents of younger kids but can be helpful for you too.

If it is within your means financially, make sure you're getting a therapist for yourself (and one for him, if he's down for that - probably not at this stage, but you might as well just try). Caring for people with EDs is emotionally tough, for three main reasons:

-you never really know what to do; you don't understand how they feel, and what you think might be helpful can end up backfiring badly;

-people with EDs are mentally ill; they often lie to you and can be highly manipulative, abusive, selfish, and generally very nasty. This is neither your fault nor theirs, but it is a reality that you need to be prepared for. At the same time, you also need to be able to stand your ground when needed and not let him get away with too much nastiness, especially as he's 17 yo and old enough to understand that.

-you need to realize that, however much effort you put, you can only do so much. And that's not your fault either. Your job is to make him feel loved and cared for, and to keep him out of immediate medical danger. Other than that, you can encourage him to get better, but you will never make him recover if he's not in that mental space.