The easy availability of affordable food coupled with a sedentary lifestyle is expanding the collective waistline of America. Fully two-thirds of adult Americans are considered to be overweight or, even worse, obese. Medical treatments of resulting health problems now cost in excess of one hundred million ($100,000,000) dollars annually. Recognition of the problem is increasing, with millions being spent on diet products, emphasis placed on physical exercise, and low-calorie fare offered on restaurant menus.

Americans are blessed with an unprecedented abundance and variety of food. Surrounded by convenient, appealing, and affordable meals, often high in calories, many Americans overindulge. A lifestyle of eating more and exercising less has led to a sharp rise in obesity. The health consequences are profound, and the social burdens substantial. Increasing numbers of Americans are recognizing that plentiful food requires intelligent choices.

For most of their six million years, human beings were hunter-gatherers who hunted, fished, and foraged for their food. Since the source of one's next meal could be highly uncertain, Homo sapiens evolved to survive a scarcity of food. Our bodies store excess calories as fat, and then convert that fat into energy when food is unavailable. This finely tuned metabolic system serves us well, but it is not designed to process steady overeating. Simply put, the body will continue to store surplus energy as fat, even when the resulting extra weight is harmful.

Lifestyle Changes

Modern agriculture ended food scarcity in America, but only in the past few years have diet and lifestyle changes produced widespread obesity. One change is that Americans consume more processed foods. These can be both tasty and convenient, and they typically are cheaper per calorie than whole fruits and vegetables. But processing often adds flavoring ingredients like sugar (11 percent of U.S. caloric intake in 1970, 16 percent today), oils, and starches.

Diets: A Bewildering Variety Americans are seemingly obsessed with dieting, and their reasons for following a specific diet vary widely. Most dieters are motivated by a desire to lose weight and, in so doing, to improve their health and appearance, but there are many other reasons. Among them are religious beliefs that proscribe certain foods; ethical rationales, such as an aversion to killing animals, a common motivation for vegetarianism; a desire to help preserve the environment by avoiding certain foods whose production is perceived as environmentally destructive, or as part of a broader philosophy of life. An amazing variety of diets are available in books, in magazines, and on the Internet. They vary widely in terms of the foods they prescribe or forbid; the emphases they place on such things as calories, fats, carbohydrates, and exercise; and on their methodologies. This plethora of choices ensures that if one diet fails to bring about the desired result, there is always another that can be tried. Here are some of the most popular diets that Americans are following today: Atkins Diet Popularized by the late cardiologist Dr. Robert Atkins Severely restricts refined carbohydrates, such as sugar and white flour Allows a wide variety of other foods, such as meat Few restrictions on fat or calories Has four phases: Induction, Ongoing Weight Loss, Pre-Maintenance, and Lifetime Maintenance Beverly Hills Diet Popularized by Judy Mazel, dietician and author Recommends eating fruit by itself Prohibits protein being eaten with carbohydrates Begins with a 35-day plan that gives specific items to be eaten at each meal Scarsdale Diet Popularized by the late cardiologist Dr. Herman Tarnower Sets forth a seven to 14-day plan Outlines types of foods that can and cannot be eaten Emphasizes fruits, vegetables, and lean sources of protein Snacking forbidden South Beach Diet Popularized by cardiologist Dr. Arthur Agatston Organized in three phases Allows normal portions of lean proteins like fish and chicken Forbids the intake of bread, rice, pasta, sugar, or baked goods in Phase 1, which lasts 14 days Allows unlimited amounts of certain vegetables but not high glycemic ones like beets, carrots, corn, and sweet potatoes Weight Watchers (registered trademark) Emphasizes a comprehensive lifestyle program including regular meetings in which dieters encourage each other Emphasizes lifestyle changes; for example, activities to reduce boredom eating All foods are assigned a point value based on fat, fiber, and calorie content No list of forbidden foods, but maximum point values should not be exceeded Fit For Life Popularized by nutritionist Harvey Diamond Relies heavily on fruits and vegetables Severely restricts dairy products and meats Attempts to teach dieters to eat in accordance with what are described as "natural digestive cycles" Vegan Diet Strict vegetarian diet that proscribes meat and all other animal products, including cheese and milk

Another change is that Americans are more likely to eat at restaurants, and especially at fast food restaurants. Americans "eat out" twice as often today as they did in 1970, spending more than 40 cents of every food dollar at restaurants. We have become especially partial to fast food. Sales have increased 200 percent over the past 20 years, to the point where one American in four eats in a fast food establishment on any given day. With the cost-per-calorie so low, Americans have grown accustomed to larger portions: on average, today's hamburgers are 23 percent and soft drink servings 52 percent larger than they were 20 years ago.

Changes in diet are related to changes in lifestyle. Americans often live alone, or in families where both husband and wife work. With less time available for meal planning and food preparation, processed foods provide attractive alternatives. A microwave oven can heat a frozen meal in minutes. Fast food restaurants feature "drive-thru" windows where a parent returning home from work can purchase dinner for a hungry family without even leaving his or her car! These meals may feature more "empty calories" (those devoid of nutrients) than a traditional home-cooked meal, but for time-pressed Americans, the tradeoff is often acceptable.

Other lifestyle changes affect the second half of the obesity equation—exercise. Physically active people burn off the calories they consume. However, Americans increasingly live in communities where both shopping and work are inaccessible except by car or public transportation. In the past 25 years, travel by foot and bicycle has declined by 40 percent. Meanwhile, the nature of work has changed. Fewer Americans engage in strenuous industrial activity. Instead, they are often sitting before a computer screen manipulating data. At home, pastimes such as television viewing and Internet surfing contribute to the general decline in physical activity, making it all the harder to shed calories and pounds. Tellingly, obesity is less of a problem in New York City, where travel by foot—to work, shopping, and entertainment —is more common than in almost all other U.S. communities.

Waistline Expansion

The result has been a rapid and unhealthy expansion of the American waistline. The number of overweight or obese Americans has increased by 74 percent since 1991. Fully two-thirds of adult Americans fall into one of these categories. (The National Centers for Chronic Disease Prevention and Health Promotion in Atlanta, Georgia, has developed a formula— known as the body mass index, or BMI— for calculating body fat in relation to lean body mass. Anyone with a BMI of 25 to 29.9 is considered to be overweight, and anyone with a BMI of 30 or above is considered to be obese. See http://www.cdc.gov/nccdphp/dnpa/obesity/defining.htm).

The health consequences have been profound. Medical treatments of resulting health problems now cost in excess of one hundred million ($100,000,000) dollars annually. It is estimated that at least 300,000 Americans die each year from obesity-related conditions like diabetes and heart disease; obesity may now be the leading contributor to premature death among Americans. Serious as these statistics are, they do not depict how excess weight can deprive one of the ability to engage in and enjoy a variety of activities common in everyday life.

Widespread obesity is a recent phenomenon, but many Americans now recognize the importance of careful attention to diet and lifestyle. Consumers pay some $34 million on diet products each year. Their results vary, as proper weight control typically requires healthful habits rather than a "quick fix." Encouraging signs include the introduction of healthier yet equally convenient snack foods and greater availability of diet-friendly entrées. Even the fast food industry reports a 16 percent increase in sales of main-dish salads over the past year.

To shed weight and remain healthy, individuals will have to consider carefully what they eat and how they go about their daily routines. Increasingly, Americans are learning that they cannot indulge without limits in what can seem to be an unlimited bounty. Among positive steps that Americans are taking in this direction are better food labeling, more nutritious and better-balanced school lunches, public awareness campaigns, and greater availability of low-calorie options at restaurants.