where does the fat go?

in the hopes of losing weight, i've returned to my healthy choice frozen entrees for lunch. i figure it's the only way i can be at school, eat reasonable portions and not eat my daily caloric intake in french fries. this led to me wonder something -- just HOW do these companies get the meals to be low fat and relatively low calorie? i suppose i could ask brimful since she is has a remarkable way of making science interesting as well as accessible. but i don't want to bother her with such stupid questions.

anyway, where's my confusion arises. i was making dinner the other day with all low-fat foods, lean meats and veggies and even a yummy dessert. i was excited at the prospect of creating such a filling, appetizing and nutritious meal that was still good for my diet. however, after eating, i used my trusty fitday to calculate my intake for the day and i realize that while the individual ingredients were all low fat/low carb/low sugar/low calorie, the entire meal was definitely greater than the sum of the parts. so HOW do these diet companies manage to make the same meals with 1/3 of the bad stuff? i suppose i'd need an arsenal of chemicals, preservatives and sodium to manage the same feat, but other than that, any ideas on how they accomplish the task?