When I decline food, I explain to people that my health and welfare require me to eat a certain way. Before going to a dinner party, I ask people if they can put aside salad for me without dressing, or even ask if they mind me bringing my own food. Other times, I’ll eat most of my own food before going, and then maybe eat salad and some fruit (and sip my green tea; red wine 1-2 glasses recommended for those who drink).
If I have to excuse myself early, to get adequate sleep, or to make time to exercise, I’m not ashamed about doing that, either. Friendship, family, and fellowship are keys to health and enjoying life. But pleasurable times with loved ones does not have to involve gluttony.