Here's one key change you can make to help get your high school waist back: Adjust your brakes.

What does that mean? Don't eat until you're full, advises Dan Buettner, author of The Blue Zones. Instead, eat until your stomach is 80 percent full.

5 Ways to Eat Less and Stop Earlier
Okinawans stop eating when they are no longer hungry, and they're one of healthiest, longest-lived people in the world. Here are some tricks that Buettner says can help you stop eating at the right time:

• Get new glasses: Choose tall and narrow over short and wide drinking glasses. You'll drink 25 to 30 percent less. Go smaller with plates and bowls as well. Check out this article to learn how to pick the perfect portion.
• Leave food in the kitchen. People who serve themselves at the counter, then walk away, eat about 14 percent less. Here are three more kitchen tricks that can help you eat less.
• Supersize with your eyes. Eat less and feel fuller by making your food look bigger. Make hamburger patties half the normal amount, and pile on the lettuce, tomatoes, and onions to make your burger appear sizeable.
• Sit down to eat. Do away with eating on the go, in the car, or while watching TV. Sit down and really pay attention to your food; you'll eat less and feel more satisfied. Here's how to practice mindful eating with a raisin.
• Weigh in daily. It sounds painful, but stepping on the bathroom scale every day may help you stay on track. Find out how this helps keep weight off.

Need more help? Use this food calculator to find out how much you're really eating.