THE OBESITY EPIDEMIC IN THE UNITED STATES—THE TIP OF AN ICEBERG
Before the last half of the 1900s, obesity was often seen as a sign of prosperity. Look at the great art of 18th and 19th century Europe and you will find portraits of the prosperous and portly prominently displayed. In the last half of the 1900s and the early years of the 2000s, obesity has become the province of the poor and the middle class.
Obesity is defined as a BMI over 30. Overweight is defined as a BMI from 25 to 30. The BMI is calculated as the weight in kilograms/height in meters squared. A BMI of 30 for a 5 foot, 8.5 inch male or female is approximately 200 pounds. To determine whether a child aged 2 to 19 years is considered obese, a BMI for age is calculated, but further assessment is needed to determine fat distribution, such as measurement of skinfold thickness. The prevalence of obesity has been steadily rising in the United States over the last 50 years, increasing over 250%. Today, approximately 20% of children aged 2 to 19 are obese, along with approximately 35% of adults.
U.S. data confirm a strong association of obesity with lower socioeconomic levels overall and in most but not all racial and ethnic groups. Overall, children and adolescents 2 to 19 years in families with an income under 130% of the poverty level (about $30,000 for a family of 4) have almost twice the prevalence of obesity as children and adolescents in families with income over 350% of the poverty level. However, these patterns do not apply to non-Hispanic black girls or to Mexican American boys or girls, in whom high levels of obesity occur at all income and educational levels.
A number of factors play important roles in giving the portrait of obesity in the United States a far less prosperous persona. The availability of cheap, high-calorie foods has played an important role in allowing access to abundant quantities of food by lower socioeconomic individuals. Newer technologies using concentrated sugars, such as high fructose corn syrup, and trans fats have reinforced this tendency. Once obesity is established, exercise may be more difficult, setting in motion a vicious circle of sedentary lifestyle and increased weight. Similarly, once obesity is established, the large quantities of food required daily often necessitate the purchase of cheap high-calorie food.
Obesity is strongly associated with a constellation of other health conditions in what has been called a syndemic, or the occurrence together of two or more health conditions. Obesity is the strongest risk factor associated with type 2 diabetes. Abdominal obesity, defined as a waistline of approximately 37 inches for males and 31.5 inches for females, is central to what is called the metabolic syndrome. The metabolic syndrome requires the presence of abdominal obesity and also includes diabetes, high blood pressure, and cholesterol and triglyceride abnormalities, including low good cholesterol. Each of these conditions can and should be treated, but treatment is far more successful and carries fewer side effects if weight can be reduced. Often a 5 or 10% reduction in body weight has a major impact on these conditions. Cigarette smoking, another strong risk factor for heart and vascular disease as well as cancer, actually has a small impact on reducing weight.
A number of approaches have been suggested to address the epidemic of obesity in the United States. An increasing number of drugs are being developed and approved to treat obesity. A surgical approach called gastric bypass surgery or more generally bariatric or weight loss surgery have been demonstrated to have efficacy using randomized controlled trials, including long-term weight loss and reduction in complications especially among those with a BMI greater than 40.
Newer dietary approaches, such as low-carbohydrate diets, have been shown in a randomized controlled trial to increase weight loss over the short run, but like other diets, the low-carb diet has less impressive results over longer periods of time. A variety of sugar substitutes have been investigated and introduced in recent years. It is controversial whether these sugar substitutes have had a substantial impact on obesity or have merely led to increased consumption of other high-calorie foods.
Other approaches attempt to get at the cultural influences on obesity, including the fact that the average portion size in restaurants has increased over the last few decades. Efforts to limit the size of high-calorie soft drinks are one example of this approach. Focusing on children and adolescents by restricting the availability of food with high sugar and carbohydrates in school lunches and offering healthier alternatives is also being tried. Taxing high-calorie, low-nutrition food is another option being debated. Increasing requirements for physical activity in schools is yet another policy change being advocated.
The answers to the weighty question of obesity in the United States remain a great challenge. What do you think we should do about it?