Inspire fat people to buy books.
$$: On its lowest levels, which they call a nutritionist, it's still pretty good, well into the mid-$100,000 level, since very needy people with low self-esteem will flock to you and never leave. At the guru level (see Guru), the money is excellent, and if you have a successful book you are truly in fat city.
The upside: Money. Sex. Power.
The downside: Can never eat a Ring Ding without looking over your shoulder.
The dark side: Posthumous decline in your book sales, particularly if you die under fat circumstances.