A few years ago I was asked to comment on an experiment a young reporter on a news show did. He went on a diet of his own design to prove that "energy in v energy out" was all anyone needed to worry about to lose weight. His plan: pies and beer. Nothing, in fact, but a restricted number of pies and beers, every day for a month.

You can probably guess the result. Yes, he lost weight. Despite the content of the diet, his energy intake was restricted. Also, the appeal of the pies quickly wore off -