Check NCBI and Pubmed. There's a lot going for ketosis and certain vegetarian diets, backed by good research.
Not saying there aren't an abundance of diet fads that find roosts the minds of uncritical hopefuls (like anything else, really), but being more conscious of what you eat and how you feel is a good thing. If the diet seems zany and tenuous but promotes portion control and variety to people who've been feeding themselves and their families out of cans and whatever is closest and cheapest, I'd tolerate if not encourage their new interest.
Some people's enthusiasms are just difficult to put up with day in and day out, whatever they might be. But in the grand scheme of it, I'd rather they be obsessed with salads than Scentsy.