I'm not doing it anymore, but I started my healthy lifestyle using Nutrisystem. I used it for about 4 to 5 months, and lost my first 40ish pounds on it. I kept on going and continued to be successful because I used the system to teach me portions and types of food to eat. From it, I began to count calories and haven't looked back since.
Word of advice: Use their chart of portion sizes along with a calorie book and you'll quickly see how the calories are used throughout the day.