And the amazing thing about this lie is that despite it staring us right in the face, pretty much everyone involved in it hasn't got a clue that they are lying or being lied to. There's no grand conspiracy here, it's just the age-old combination of wilful ignorance pushed on by the dangerous mix of greed and desperation.
That lie is the diet book industry.
A quick perusal of the annual non-fiction bestseller lists in the UK will show you the preeminent position of "healthy recipe" books and fad diet manuals. They aren't just big business, they are often the publications that publishers live and die by.