Note that the Amish have the diet thing figured out. They eat the good stuff, and stay lean because they are physically active. The Amish evidence implies that McDonalds should be absolved of blame for our bulging waistlines. Instead, point the finger at labor saving technology and slow adaptation of eating habits to diminished physical activity. Economists Darius Lakdawalla and Tomas Philipson examine this hypothesis in depth. They find that differences in food prices and technological diffusion explain a large fraction of the variation in weight gain across different populations.