long distance problem!

Hi! Ive been with my bf for 2 years. We see each other monthly. I have a problem and idk what to do!!! We are in college and everytime I see him he looks bigger and bigger. He keeps eating so bad and in less than a year has gained 30+ pounds. He knows this and complains but makes no action. I have tried telling him to eat better/workout competitions but he never follows through. What am I to do? I care about his health! We went to the store today and i was walking fast but i was at the end of an aisle that he started. Im in no amazing shape but come on. What do I do? I dont care how he looks but he is being heathy and not happy(complains). I dont want to be too direct because that would make me upset if someone did that but what else can I hint at??? Ps hes not depressed/upset. He has a great life,family, social, academics ect. Im just worried for the future his health and when he actually has stress from work/bills ect.