How can I not be tempted to take a lot of food at parties?

I am a 20 year old man, 5'7" 141 lbs. I am not obese, I often work out, and eat well. If a party is buffet style I often take more than I can eat and eat it all. Since obesity runs in my family I often want to destroy these habits so it doesn't haunt me in the future. Is there anyway to defeat this habit?