nit 1: Saturated fats; an example of market failure?

The food standards agency has just launched a new campaign viewable via the bbc at

http://news.bbc.co.uk/1/hi/health/7878680.stm

a) In what way might the consumption of saturated fats represent market failure in the form of a demerit good?
b) Using a diagram explain how this campaign might reduce the market failure