Gluttonous is impossible: it an adjective and can’t take the determiner a. How do you use the noun from which it is derived, glutton? If you were using the term gluttony to describe the seven deadly sins of the Bible, a doctor would never use it to a patient.

If someone is overeaten, it’s possible. Is there reason for telling something like an overeater? I speak under correction by the physicians on this site, but I think a doctor would instead address the patient’s actions:

You are eating too much?

Why is there a particular problem that can be corrected with love? I’m an old guy, and we should talk about the solutions and not the problem. You will need to focus on

sugar and starches in your diet and eat fruits. If you want to have a healthier and more balanced lifestyle. If you can’t, don’t neglect to look after your mind.

What is the importance of transparency?

Most of the words ending with “ous” are actually adjectives: they need nouns, which is the case here as well. So no, you cannot say “You are a gluttonous guy.” Is it possible to say “You are a cheesy”?

What is glutton?

I’ll say that I haven’t heard this word used before, so that may not be understood just because it is rare word.

Is “You are an overeater” commonly used? I usually hear “overeat” used by someone who has eaten too much, not in that particular form.

What do you think about “Person A”?
Person B : I was really good, but I think I overate…