Does serving size matter? This study says yes.

Does how much you're served affect how much you eat? Researchers put mac & cheese to the test.

When people in the study were offered a 580-calorie platter of macaroni and cheese for lunch, they consumed an average of 420 calories. But when they were offered a larger, 1,015-calorie platter, they ate 595 calories.

(The study was funded by Jenny Craig.)

What to do

Watch out for large servings, especially at sit-down restaurants, where a typical entrée tops 1,000 calories.