The human life expectancy has steadily increased over the past few centuries; however, the current generation may be the first with a shorter life expectancy than their parents. The reason behind this unfortunate reversal is not increasing cancer rates or development of resistant bugs or new viruses, but a global increase in obesity and associated comorbidities.1
Obesity is defined as an excess accumulation of body fat and is commonly defined as a body mass index (BMI) of >30 kg/m2. In the United States, obesity affects 40% of women, 35% of men, and 17% of children and adolescents. In 2014, there were 600 million obese patients worldwide, with several countries having obesity rates greater than those in the United States. The highest rates of obesity can be found in some of the Pacific Island nations where obesity rates are greater than 40%. Obesity has been classified into several subcategories, as summarized in Table 36-1, with estimated prevalences from the National Health and Nutrition Examination Survey (NHANES) 2013 to 2014 data.2 Severe obesity is often regarded as BMI ≥40, or ≥35 with obesity-related comorbidities. Superobesity is defined as a BMI ≥50.
TABLE 36-1PREVALENCE OF OBESITY AND SUBCLASSES IN THE US POPULATION ||Download (.pdf) TABLE 36-1 PREVALENCE OF OBESITY AND SUBCLASSES IN THE US POPULATION
|BMI ||Classification ||US Prevalence |
|Overall % ||Men% ||Women % |
|≥30 ||Obesity ||37.7 || 35 ||40.4 |
|30.0-34.9 ||Class I obesity || 30 ||29.5 ||30.5 |
|35.0-39.9 ||Class II obesity || || || |
|≥40.0 ||Class III obesity (morbid) ||7.7 ||5.5 ||9.9 |
With the growing obesity epidemic, there has also been an increase in the prevalence of morbid obesity over the past decade, with a linear growth in the rate of morbid obesity in women.
Although BMI is easy to calculate and has become the universally accepted measure for defining and classifying obesity, it is not ideal and has several limitations because it does not directly measure excess fat accumulation. As a result, a 70-inch muscular and fit athlete who weighs 215 pounds and has a BMI of 31 will be regarded as obese even though they have little excess fat accumulation. Although one can define obesity as percent body fat >32% in women and >25% in men, these calculations are difficult. More importantly, neither BMI nor percent body fat calculations provide any information on the regional body fat distribution. This is important because intra-abdominal and visceral obesity is associated with greater risk of insulin resistance, hyperlipidemia, hypertension, cardiovascular disease (CVD), and stroke than peripheral fat distribution. This difference is important because those with central obesity (android or apple pattern of obesity) have a greater risk of diabetes and CVD than those with fat accumulation in the subcutaneous tissue of buttock areas (gynoid or pear pattern of obesity). This difference in fat distribution may explain why individuals of ...