Back when I was at Tucows, a couple of young ladies started a fitness program based on Weight Watchers. They taught us the system, which was dead simple, and we met on a weekly basis to celebrate our victories and commiserate over our losses. (Well, in his case, it was gains.)
The system distills down to this: based on your age, weight, sex and activity level, you are assigned a certain number of points. Each food you eat has a point value calculated from calories, fat and fiber. You simply make sure you don’t eat more than your number of points per day.
I set up a couple of calculators to determine your daily points allowance, and food points.