Why not, though? Eating is fun and pleasurable. If we can figure out a way to eat the things that we want, in the quantities that we want, while maintaining our health, why shouldn't we try?
I've lost weight through forcing myself into a calorie deficit, and it works really well, but it's not particularly fun.
Did you get an iberian to lay the pattern in your vomitorium?
You always end up with the people pushing these foods being those who sell them. And then others start selling fake foods with similar claims.
For the "eat to get slimmer" claim, I think we're at the point where "extraordinary claims require extraordinary proof."