Meal Replacements and Diet

My friend is trying to lose weight. He says that it’s half diet and half nutrition. That part I don’t have a problem with. What I do have a problem with is that he is spending his hard earned money on these meal replacement packets. He’s 6’ 1" probably weighs 220, maybe 235 tops. Were about the same strength (maybe I’m a little stronger as I can do more pull-ups) but I’m 30 lbs lighter. He wants to get down to my weight and size. I told him to eat healthier. He says that it takes too long and he doesn’t have enough time to prepare healthy meals. The stuff he wants to buy is like SlimFast, but it has a lot of protein and low fat. Isn’t this just like eating SlimFast? Won’t he gain the weight back after he stops taking it? Does it work? My mom took SlimFast with moderate success. She was slimmer, not exactly stronger, and not exactly like my friend’s goal of Brad Pitt in Troy.