My bf is eating too much

My bf always eats too much, like 3-4 servings at family dinners and I don't know how to tell him that he's coming off as a bit selfish and glutton.

My family (7 people with me) hasn't complained but I was raised being told that you should always hold back on food so that everyone can eat or at least have a taste. We're kinda poor :/

My bf lives alone with his mom and food hasn't been a big issue but his mom does call him chubby (he is a bit chubby but no biggie) and joke about his weight. I really don't want to make him more self conscious than he already is but I want us to be more healthy.

We're also planning a trip to my home country and my family back there isn't exactly rich :/ . I guess that I'm just worried that he'll eat too much and that we won't have enough food for everyone.

How do I tell him to slow down on food without hurting him?

Edit:

My bf is definitely eating too much because he doesn't know how to control himself. His mom is bulimic and he'll eat until either there's no food left or until he gets a stomachache and has to run to the bathroom to "calm down". He'll eat half an extra-large pizza and then ask for dessert at supper (17h) and then he'll stop eating until the next day at 15h. He starves himself and then almost binge-eats.

I'm asking for genuine help not your judgement. I'm not superficial and I love him with all my heart and soul. I just can't help worrying about him. I don't care about his appearance but we have both been gaining weight and I'm prone to iron deficiency. We've been together for almost 3 years and we're both in our 20s and not that active.