My boyfriend isn't very health conscious, how can i get him to be more healthy?

Reward/penalty: The reward/penalty system works for most people, if a person is 'rewarded' for learning or doing something positive, they will strive to repeat that event. Conversely, if harmful habits are 'costly' in terms of affection, favors or compliments...They will tend to avoid them. Eventually, the intrinsic benefit of healthful living will become clear.