Brilliant series available on BBC Iplayer is Horizon –
the recent episode about Fat vs Sugar follows a pair of twins (who are both incidentally doctora). For one month they change their diets completely – one doctor gives himself a diet based on high fat, low sugar (such as cheese, meat, dairy, low fruit and veg) and the other doctor has a diet of high sugar and low fat ( such as bread, pasta, rice, potatoes, fuit and veg, sugary drinks ) for the duriation of this month. The effects are startling and the information on the nutrients that the body needs is really interesting. Of special interest is the changing levels of insulin sensitivity of the pair. Well worth a watch !!