Researchers offered participants an unlimited quantity of the same pasta-tomato-pesto salad labeled either “light” or “filling” for lunch on separate occasions. On average, the participants consumed more calories from the “light” salad (469) than from the “filling” salad (427).

What to do

Labeling rules require a food that’s “light” in calories to have at least a third fewer than usual. But that doesn’t matter if you pile it on.