In a recent report on longevity the Japanese island of Okinawa was extolled as one extremely healthy place to live and age. Aside from having an elderly friendly culture and an exceptional diet (lots of fish, soy and a colorful array of veggies), Okinawans follow the philosophy of hara hachi bu, meaning eat until you're only 80 percent full. A little different from the stuff yourself silly mentality behind those all you can eat buffets.
Typically, Okinawans eat about 1200 calories a day, which is about 20 percent less than the average Briton. Interesting figure don't ya think? I think it is a great way to eat and reminds me of advice a yoga teacher gave me a good long while ago. Eat just enough so you can practice yoga after your meal. That is, eat so you have enough energy to practice but not so much that practicing yoga would be uncomfortable.
Try it at your next couple of meals. Of course this requires eating mindfully as well, which is another healthful eating practice.