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Visitors to the United States are often struck by the signs of obesity to be seen everywhere. In Europe, indeed, the old stereotype of the “Ugly American” tourist is being replaced by the caricature of the “Fat American.” The percent of Americans adults who are obese increased from 12% in 1991 to 18% in 1998. Another large fraction of America’s population is also above a healthy weight but below the formal definition of obesity. Half of all Americans, indeed, are either overweight or are obese by World Health Organization standards (see Text Box below). Obesity rates in children are also rising fast. This obesity epidemic is global, and includes many East European and developing countries. For example, the rates for being overweight and obese in Mexico, Kuwait, and in parts of South Africa are similar to or exceed those in America. In Russia, surveys show that 30-35% of women and 10-15% of men are obese; in the former East Germany obesity rates are 20-30% for women and 15 to 20% for men. Moreover, as obesity spreads it is changing. No longer is obesity a luxury of the rich; instead, it is an affliction of the poor. In affluent countries, indeed, obesity is now two to three times more likely in people with the lowest educational attainment. The health consequences and the costs incurred in treating the complications arising from obesity and excess weight are enormous. In America, excess body fat accounts for about 90% of adult-onset diabetes, about one third of heart attacks, contributes to several major cancers, arthritis, cataracts, and reduced quality of life in general. Disconcertingly, the form of diabetes previously only seen in adults is now commonly seen in adolescents. Although genetic factors influence the likelihood of obesity, they cannot explain such massive increases in so short a period of time. Fundamentally, weight gain occurs when physical activity decreases or total caloric intake increases. An epidemic of obesity should come as no surprise because many aspects of contemporary life promote it. Convenient transport and sedentary occupations dramatically reduced physical activity throughout the world. Eighty percent of the world’s population now has access to sufficient food. A great accomplishment, but consuming even a small amount of food above the necessary will lead to obesity within a few years. With opportunities to eat ever present - fast food shops, ready-made dinners - human weaknesses to indulge are fully exploited. What should be done? We should first recognize that obesity does not come from eating fat. People eat less fat now and are more obese than ever. Indeed, medical trials show that fat and carbohydrates have similar effects on body fat. So those faddish no fat, high carbohydrate diets are doomed to fail. The urban poor in developing countries show that high rates of obesity occur when limited physical activity is combined with simple starchy diets. How can obesity be controlled? Although many dream of a pill to cure the problem, a safe and effective drug does not yet exist. So instead of looking for a magic bullet we should recognize that obesity is a function of social change: urbanization, sedentary lives, and the consumption of mass-produced high caloric foods. In principle, if each individual just exercised regularly and was careful about caloric intake, obesity would be uncommon. But because low levels of physical activity and over-consumption are deeply imbedded in our lifestyles, individuals acting in isolation face many obstacles. An effective strategy to fight the obesity epidemic will require both individual and institutional initiatives: • nutritionists must provide improved dietary advice and make it accessible to all; • health care providers can do more to counsel patients about the importance of minimizing weight gain as adults; • schools and businesses can require daily physical activity, serve healthy meals, and integrate health education into their routines; • parents can limit television watching, not buy soft drinks, express love without high-calorie sweets, and be good role models in their diets; • governments can provide facilities for safe walking, bicycle transportation, and recreation. Although we willingly spend massive amounts of money to treat the diseases and health complications that arise when so many people are so overweight, we are reluctant to invest even modestly in strategies that can prevent the underlying problem. This must change if the obesity epidemic is to be contained. Preventive strategies are particularly important in poor countries. During the next 30 years, United Nations demographers predict that two billion people will be added to the world’s population. The large majority will be in poor urban areas of developing countries, places where some of the largest increases in obesity are now being recorded, and where provision of expensive medical care is difficult. Sadly, these cities are typically expanding without including safe facilities for recreation. Such facilities are not expensive to include when streets are being created, but are costly to build retrospectively. They should be required components of all urban planning. Can prevention work? Many individuals, having learned to exercise and avoid excessive caloric intake, are controlling their weight. The shift of the obesity burden from the rich to the poor in many Western countries demonstrates that knowledge and the ability to act upon it are important. We also have examples of whole countries - Holland and some Scandinavian countries - where exercise is encouraged by the inclusion of bicycles and pedestrians in urban design. The obesity epidemic can be controlled, but everyone’s effort is needed. TEXT BOX What is Obsity? Obesity is excessive body fat, but this is difficult to measure directly. For this reason, body mass index (BMI), which is a measure of weight corrected for differences in height, is most commonly used to define obesity. BMI is computed as weight (in kg) divided by height-squared (in meters). The World Health Organization has defined a BMI of 30 or greater as obesity. Overweight is defined as a BMI of 25 to 29.9. Although the health risks for being overweight, including diabetes, heart disease, and some cancers, are less than those for obesity, they are still substantial.