My roommates are getting bigger, some to the point where it's getting unhealthy, should I do something?

I live with 6 other girls. 2 are also American, 2 from malysia, one from china, one from england and one from ireland. And this particulary true for the Asian girls. When they got here last year they were all super skinny and they must have gained 30 lbs last year. When they went home from the all lost a lot of weight and now they're gaining it again. I'm wondering if I should say or do something.

The two Americans were kinda chubby to start with and are getting bigger and bigger to point where I would it starts to become unhealthy. The irish and English were also super skinny when they got here and keep gaining weight. It seems like I'm the only who actually lost weight in college.

But what could you do? We usually only share one meal which is pretty healthy. I guess they just have a lot unhealthy snacks and eat lots of fruit loops for breakfast. I really like all of them and it's sad seeing them getting so much bigger. But what could I do without being hurtful or like imposing my lifestyle on them?
My roommates are getting bigger, some to the point where it's getting unhealthy, should I do something?
Post Opinion