Pritikin Recipes

A friend of mine has a daughter who really needs to lose some weight. She just turned 13, and she is over weight by about 10 pounds. What is an easy to stick to diet that doesn’t involve going to great lengths like ordering some brands of planned-out diets or cooking especially elaborate meals? If you could just give me some simple tips, that would really help. Thanks in advance!!

My question again was about diet cooking tips and there have been some great answers