This might sound strange....Apologize for nagging. Qualify that by saying that he IS an adult, and he knows best about his health, and what to do.

Then DROP it. Totally.

Based on some stuff I have read - men really feel disrespected when treated like little boys who don't know what is good for them (I know I know ).

So trust him to be a grownup who knows what is best, and let him know that.

ANY nagging or sarcasm just puts his back up - and he forgets about being healthy - because he'd rather be right and defend himself than be healthy!

Reduce his options.