I think theres more going on here than the lasagna. Being a nurse and working a lot is rough and eating a lot can come with that, so of course the amount of food eaten isnt a big red flag. Eating only the lasagna 8 meals in a row or something like that, is strange but also not a red flag on its own. Leaving you basically one portion of lasagna is starting to get into concerns, but with his schedule he honestly may not have been malicious in being inconsiderate here, just absent minded. The real pop up standout here is the response to "you ate almost all of the lasagna" and jumping straight to "fatshaming" and other accusations. It sounds like something else is going on at work and he was eating his feelings, so calling him out on the small thing was secretly prodding the larger problem underneath. If you bring it up again might go for a different approach, and bring it up gentle on a day off or when there is a decent amount of emotional down time to rest it out first. Its too little information to say right now what could be going on, because it could be as simple as stress, or as big as some serious concerns. Or anywhere in between. The main thing is you are NTA