"I like you a lot and would be with you no matter how much you weighed but it would make me so happy if you could lose some weight for your physical and psychological well being and also for the sake of our relationship."
I don't know. . . it seems sort of odd that you would enter a relationship and immediately start trying to change major things about him. Why even enter the relationship if you knew from the beginning you didn't like him as he is?
Since it is new, just .........honesty. Best way to begin any relationship.
Take him hiking and many other places that require activity. One have fruits, veggies, and diet drinks in your house.
Well.. What are you talking about?
A couple pounds overweight or morbidly obese?
But how much overweight?
Do you exercise frequently?
Maybe do activities with him? Like jogging? Or a sport?
If you do it with him or ask him to go with you it doesn't seem so offensive