But there's a hidden cost to those larger portions, even beyond the health consequences of gaining weight. A team of University of Wisconsin-Madison nutritional scientists has calculated how much money a single bout of overeating can cost over the following year, according to a study to be published in June 2006 in the Journal of the American College of Nutrition.
"When confronted with the overwhelming costs of obesity to society as a whole, people don't always take the statistics personally," says Rachel Close, who completed the study with professor of nutritional science Dale Schoeller as part of her master's thesis. "This is another way to present the costs associated with weight gain, and might help convince people that upsizing a meal is no bargain after all. With obesity projected to rise from the current 30 percent to 40 percent of the American population by 2010, this is an important message."
Schoeller and Close were interested in how additional weight affected the amount of money spent on medical care and a vehicle's gasoline mileage, as well as the cost of the additional caloric energy required to support increased body weight. The pair anchored their study on two key assumptions: that the additional calories from upsizing a fast-food meal would be stored as excess energy -- in other words, that they would lead to weight gain -- and that diners would not compensate for the excess calories during subsequent meals. Close notes that the results of this study apply to overeating regardless of the type of food consumed -- fast-food or a home-cooked meal -- as long as the diner does not compensate for the calories at a later meal.
After averaging the prices and caloric difference between regular and up-sized french fries and soft drinks at three major fast food chains, Close used studies of body mass index and medical cost, average vehicle mileage and gas prices, and caloric expenditure to calculate how the weight gained from one upsized fast-food meal translates into money out of pocket over the next year.
They found that for the initial 67-cent average cost of upsizing a fast-food meal -- and the subsequent 36-gram weight gain -- the total cost for increased energy needs, gasoline and medical care would be between $4.06 and $7.72 for men and $3.10 and $4.53 for women, depending on their body type.
The bottom line: Although upsizing a meal brings you 73 percent more calories for only an additional 17 percent in price, the hidden financial costs drive the price of that meal up between 191 and 123 percent.
"While there's an immediate savings in upsizing a meal, we've shown that the hidden costs balance that initial savings, and actually surpass it," says Schoeller. "People might choose to change their behavior because of financial consequences, if the health consequences of obesity are not yet a factor in their lives."
Close and Schoeller's study was supported by the National Institutes of Health.