4/4. Faced with vast amounts of information about the food we eat, how do we decide which messages to believe? Roger Bolton meets politicians, nutritionists and food manufacturers, all of whom have good reasons for trying to influence the choices we make about our food. And as Britain faces up to an epidemic of overeating, what steps should the Government be takingto persuade us to adopt a healthier diet? Producer John Watkins Repeated at 9.30pm