Austerity and sacrifice, let alone starving oneself in the name of slimming down, are off the table -- it's counterproductive and dooms us to long-term failure.
Instead, I try to follow these principles. Here's the list, with elaboration on #1 below. Over the next week or so, I'll elaborate on the others.
1. Cook your food
2. Eat nine servings of fruits and veggies per day
3. Exercise (in a variety of forms) 45-60 minutes per day
4. Avoid supermarket and fast-food meats
5. Minimize liquid calories
6. Eat good fats
7. Snack smart
8. Monitor your health
9. Take it easy at restaurants
10. Eat breakfast every day
#1 Cook your food:
This is a simple one, really: we should eat most of our meals at home, and prepare them ourselves.
I'm all for using kitchen shortcuts, such as buying pre-peeled and cut veggies, but in general your meals will be healthiest when made yourself, from scratch.
Otherwise, you really don't know what's going in your mouth.
I heard food author Michael Pollan say it's OK to eat as much "junk food" as you want--as long as you cook it yourself. He was talking about French fries, which used to be a very occasional treat for most people, if only because deep-frying potatoes makes a huge mess in the kitchen and most people don't want to hassle with that very often. Now you can drive through a fast-food joint and get a piping hot, salty hit of crispy potatoes any time of day or night, any day of the week. Insanely, French fries are by far the most widely consumed "vegetable" in the U.S.
But if you only ate them when you made them yourself, how often would French fries be on the menu? If you do want to make your own "fries," try doing them in the oven. Better yet, make them with sweet potatoes rather than white ones.
Take-away point: eat most of your meals at home, and bring a lunch from home with you to work. You'll be healthier and slimmer as a result.