It used to be but I don't think it's like that anymore. When I was younger it was indeed like that but back when I was anorexic I saw a lot of healthy eating blogs (And no they didn't disgust me), most were American, and they HATED when people called it a diet. Absolutely were offended. They would constantly say it's a lifestyle. I think it's both and then when the diet (Losing weight) parts done it's just a lifestyle.
Also on this American forum website called bunspace.com (For bunny rabbit owners-which I am-I'm am not an active member anymore) they have this thread and the motto of it is "Make it a habit, eat like a rabbit!" haha
Anyways this is just to my knowledge-maybe older people still do this?