One of the reasons I left a gym is because of their strong pressure to sell a certain product (not Isagenix). My personal feeling is that while most meal replacements won’t harm you, they don’t teach you anything about good eating habits. Most weight loss from restricted-calorie plans and cleanses where people just eat bars (and shakes and powders) is gained back once the client stops eating the bars (and shakes and powders).
My personal preference, within my scope of practice as I am NOT a nutritionist, is to talk about developing healthy habits, one at a time, that can be maintained. Small, consistent changes lead to long term sustainable results.
The behavior that underlies the eating habits MUST be addressed.