The idea that increasingly overweight Americans are weighing down airplanes may seem funny to the average person, but it is no laughing matter for the airline industry.

According to a study by the Centers for Disease Control and Prevention, accommodating the extra weight gained by Americans over the past 10 years cost airlines around $275 million in 2000, which appeared in the October issue of the American Journal of Preventative Medicine.

The study highlights how fuel costs have risen because of heavier passengers on planes, according to Jennifer Sarginson, media officer for the CDC.

"The purpose was to look at the unexpected consequences of obesity in the United States," Sarginson said.

The effect of obesity on the airline industry is an area that had not been looked at before, she said. The weight gain of people who are not obese is also important in the study.

The CDC study estimated that the average American man in 2000 is eight and a half pounds heavier than the average man in 1994. The average American woman's weight increased 11.4 pounds in the same time frame.

To compensate for the additional weight from passengers, airlines have made adjustments to decrease the load of other objects on planes.

"Everything that goes into the aircraft is evaluated from a weight perspective," said Carol Skornicka, a spokeswoman for Midwest Airlines.

To reduce the amount of weight on Midwest Airlines' planes, Skornicka said the company has done everything from ceasing to use heavy utensils to reducing the number of magazines on flights.

Even with reduction of other objects on planes, 10 pounds have been added to the additional person when calculating a flight's weight balance, Skornicka said.

The extra 10 pounds were added on to the Federal Aviation Administration's previous recommendation to calculate adult weight at 180 pounds in the summer and 185 pounds in the winter, according to the CDC study.

"The FAA has recognized that the average passenger weight is greater than it was," she said.

The increased weight of Americans has resulted in some airlines requiring obese passengers to purchase an extra seat.

Southwest Airlines has implemented a policy that require passengers who will not comfortably fit into a seat to purchase two, according to spokeswoman Whitney Eichinger.

Eichinger said there is not a specific weight at which Southwest will mandate a customer to purchase two seats.

"A lot of times the customer will know before that they need two seats," she said.

She said if a passenger arrives at the airport and cannot fit into a single seat, a second one may be purchased there. If the plane is not full, the person will not be charged for the second seat.

The policy intends to control weight on flights and increase comfort for passengers, according to Eichinger.

"You get customer letters from both sides of the story, those who felt like their space was invaded or needed more room," she said.

Midwest, on the other hand, has never required anyone to purchase an additional seat, Skornicka said.

"I don't think anybody's talking about charging different amounts for different weights," she said. "We're not going to weigh people."