The Obesity Epidemic
Section snippets
Rapid rise of an epidemic
Many public health officials and organizations have tried to alert the public about the dangers of obesity.1 Reports estimate that obesity was responsible for approximately 365,000 preventable deaths in 2000.1, 2 This number was second only to that attributable to tobacco smoking. More recent reports indicate that obesity lessens life expectancy markedly, especially among younger adults.3 Despite this knowledge and the increased media coverage about the health, social, psychologic, and economic
Definitions of overweight and obesity
Overweight and obesity are currently defined based on body mass index (BMI), which is determined as weight (kilograms) divided by height (square meters). Table 1 shows the categories of BMI. A healthy BMI range is 18.5 to 24.9 kg/m2. Overweight is defined as a BMI from 25 to 29.9 kg/m2, and obesity is defined as a BMI of 30 kg/m2 or greater.7 Obesity can further be subdivided based on subclasses of BMI, as shown in Table 1. Extreme obesity is defined as a BMI greater than 40 kg/m2. Waist
Prevalence of overweight and obesity
The strongest data on obesity prevalence rates over time in the United States come from the results of the NHANES. The NHANES periodically collect measured heights and weights in representative samples of the population for adults, adolescents, and children in the United States. The most recently reported NHANES data were collected during the period 1999 through 2006.9, 10 As shown in Fig. 1, obesity rates in adults (20–74 years of age) have been gradually increasing over the past 3 or more
Gradual fattening of Americans
Hill and colleagues24 examined the trends in the increase of obesity in the United States. Their analysis suggests that the obesity epidemic arose from gradual yearly weight gain in the population produced from a slight consistent degree of positive energy balance (ie, energy intake exceeding energy expenditure). Using longitudinal and cross-sectional data sets, they found that the average adult in the United States has gained an average of 1 to 2 lb/y for the past 2 to 3 decades. Fig. 14, from
Health risks associated with obesity
Obesity is linked to the most prevalent and costly medical problems seen in our country, including type 2 diabetes, hypertension, coronary artery disease (CAD), and many forms of cancer. Box 1 lists the complications and diseases that are directly or indirectly related to obesity.
Obesity is a Disorder of Energy Regulation
The size of the body fat mass is the result of the balance between energy intake and energy expenditure. If energy intake is sustained at a level that is too high for a given level of energy expenditure or if energy expenditure is sustained at a level that is too low for a given level of energy intake, obesity develops.55 Such a simple statement fails to reflect the complex nature of obesity and the numerous biologic and environmental factors that have an impact on energy balance (Fig. 16). We
Dealing with the complexity of obesity
The more we understand about the etiology of obesity, the more complex it seems. Obesity involves interaction between our biology, our behavior, and the environment in which we live. We have efforts underway in our scientific community to focus on each of the major issues but few, if any, efforts to integrate among areas. Focusing only on one of these major areas is likely to be incomplete. We need to understand the underlying biology of obesity, but only in rare cases is obesity the result of
Strategies for getting out of the obesity epidemic
It is important that we begin to craft strategies that could get us out of the obesity epidemic. Fig. 21, adopted from the work of Dr. Stephan Rossner, illustrates some possibilities. If we do nothing, the weight of the population is likely to continue to increase until a time when all those who are not genetically protected are overweight or obese. How might we reduce obesity prevalence rates to acceptable levels over time?
One possibility is to reduce weight in many of those people who are
Summary
In pursuing “the good life,” we have created an environment and a society that unintentionally promote weight gain and obesity, given our genetic and biologic make-up. The consequences of the obesity epidemic are severe, affecting the health, quality of life, and economics of our nation. Dealing with the epidemic of obesity is likely to be one of the greatest challenges our society has faced. To reverse the obesity epidemic, we must develop specific strategies that recognize the complexity of
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This work was supported by grant K23 DK078913-02 from the National Institutes of Health.
Portions of this article were adapted from Hill JO, Catenacci V, Wyatt HR. Obesity: overview of an epidemic. Psychiatr Clin N Am 2005;28:1–23.