All weight loss books, if they are truthful, boils down to: eat healthy, exercise more, everything in moderation. That doesn't really make you money, which is what the author actually want. Other categories are equally padded, or the topic has been sufficiently covered for 2000 years or more.

The whole spiel about "I just want to help others in the same situation" died with the Internet, because for the past 30 years it has been entirely feasible to publish your advice and guidance for for free. The books are just for money and fame.