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The worldwide obesity epidemic is the result of many widespread lifestyle changes that occurred during the 20th century. In the past, more people ate low fat diets and engaged in daily strenuous physical activity; today, more people eat high fat diets and lead sedentary lifestyles. More than one billion of the world's adults are overweight, about 300 million of them so much so as to be labeled clinically obese. Obesity presents a serious threat to public health, since the overweight population are vulnerable to a range of diseases associated with obesity, including type 2 diabetes and heart disease.
Medical professionals generally use the Body Mass Index (BMI) obesity scale to determine which patients are overweight and which are obese. A person with a normal, healthy body weight has a BMI of 18.5 to 24.9. An overweight person has a BMI of 25 to 29.9, and an obese person has a BMI of 30 or higher.
The causes of the global obesity epidemic are many and complex. The 20th century saw worldwide modernization, urbanization and economic growth. Around the world, incomes have risen, diets have changed to include more processed foods that are high in sugar and fat, and life has become less physically strenuous; the rise of technology, automated transport and passive leisure activities have drastically reduced the amount of physical exercise the average person gets each day. The appearance of globalized food markets sounded the death toll for traditional diets in many indigenous cultures; for example, the Pacific Islanders of American Somoa once ate healthy diets comprised of native fish, coconut, yams, bananas and taro root. In the postwar period, exposure to Western culture led to Westernized eating habits; American Samoa has become one of the fattest countries in the world—93.5% of its population is overweight or obese.
The global obesity epidemic may be threatening to cripple the world's health-care systems, as doctors struggle to cope with the medical consequences of obesity, including heart disease, cancer and diabetes. Obesity in the United States is on the rise, and includes more children and teenagers than ever before. Experts stress that only a comprehensive public health campaign can reduce global obesity rates and prevent future generations from becoming obese. Since the world's health-care systems don't have the resources to treat the complications associated with obesity, the world's overweight population must be educated and encouraged to pursue healthier lifestyles.
The World Health Organization believes long-term, worldwide cultural and social changes are needed to stem the obesity epidemic. Experts argue that low-fat, energy dense and nutrient-rich food should be made available as a matter of public policy, and all populations should have access to fitness and sports opportunities. Comprehensive public health campaigns have been suggested that would stress the importance of a low fat, low sugar, high carbohydrate diet based on fruits, vegetables and whole grains, and include thirty minutes of moderate exercise each day. Experts agree that losing even a small amount of weight can protect the obese from the complications associated with their condition.