Food stacking is the idea — popular in some diet circles — that nutrients should be eaten in a particular order so they can be digested “in the most efficient manner.” A common version advises eating fruit first, then vegetables, then proteins and starches, on the theory that each layer digests cleanly before the next arrives. There is no physiological basis for this: the stomach churns mixed meals together, enzymes for all macronutrients are secreted simultaneously, and the gut absorbs nutrients from the resulting chyme regardless of the order of eating. While eating vegetables or protein before starches can modestly blunt post-meal blood glucose rises, the elaborate stacking rules themselves are unsupported, and dietitians regard them as another variant of food-combining mythology.