How often have you heard someone say, after pushing back from the table following a hearty meal and ruefully patting his or her belly, 'It isn't me-it's my metabolism'? It's easier to blame our girth on the slow rate of the chemical reactions that convert the food we eat into the energy we need to live than it is to take responsibility for the amount and kind of food we put into our mouths, and although disorders like hyperthyroidism and diabetes...