About 70 million Americans are trying to lose weight．That is almost 1 out of every 3 people in the United States．Some people go on diets．This means they eat less of certain foods, especially fats and sugars．Other people exercise with special equipment, take diet pills, or even have surgery．Losing weight is hard work, and it can also cost a lot of money．So why do so many people in the United States want to lose weight?
Many people in the United States worry about not looking young and attractive．For many people, looking good also means being thin．Other people worry about their health．Many doctors say being overweight is not healthy．But are Americans really fat?
Almost 30 million Americans weigh at least 20 percent more than their ideal weight．In fact, the United States is the most overweight country in the world．'The stored fat of Americans weighs 2．3 trillion pounds,' says University of Massachusetts anthropologist(人类学家) George Armelagos．He says burning off that stored energy would produce enough power for 900,000 cars to go 12,000 miles．
Losing weight is hard work, but most people want to find a fast and easy way to take off fat．Bookstores sell lots of diet books．These books tell readers how to lose weight．Each year, dozens of new books like these are written．Each one boasts to help people to get rid of fat.
Which of the following is NOT mentioned as a way of losing weight?