In 1910, Americans got almost 60 percent of their calories from carbohydrates; by 1980 the figure had fallen to 43 percent. The gap has been filled in by fat.

Or, to put it in 20th Century terms, the way to lose weight is to eat less, especially fat, and exercise more. Hardly new concepts. Most people have long since tired of hearing them.

There are several reasons why fatty foods go directly to your hips and thighs and carbohydrates do not. For one thing, a gram of fat has 9 calories, whereas a gram of carbohydrate or protein has only 4. So fat has more caloric density.