Restaurants are beginning to experiment with smaller portions on their menus, but since portion Supersizing has meant increased profits (and expanding American waistlines) for years, it's a risky play. "Larger portions are so profitable because food is relatively cheap. On average, food accounts for about a third of the total cost of running a restaurant; such things as labor, equipment, advertising, rent and electricity make up the rest. So while it may cost a restaurant a few pennies to offer 25 percent more French fries, it can raise its prices much more than a few cents. The result is that larger portions are a reliable way to bolster the average check at restaurants."