The obesity problem in the United States has reached epidemic proportions – and it's only getting worse. It is a multifactorial problem, the unintended consequences of the economic, social, and technological advances realized during the past several decades.1-3 The increasing prevalence of obesity is a major public health concern, since obesity is associated with several chronic diseases. An increase in obesity among U.S. adults continues in both sexes, all ages, all races and all educational levels.3 Among adults, obesity prevalence increased from 13 percent to 32 percent between the 1960s and 2004.3 In 1991, only four states had obesity rates of 15 percent or higher, while in 1998, 37 states had exceeded this level.1 Currently, 66 percent of adults in the United States are overweight or obese.3
Measures of Obesity
Adult overweight and obesity are defined by using a measure of weight in relation to height.3 The universal formula in medicine is kg/m2, referred to as body mass index (BMI). The concept was introduced in the 19th century by Quetlet in a social physics course and in 1972 it became known as the body mass index. The formula was initially designed to be used in population studies and not as a diagnosis of individual overweight or obesity. Currently, a BMI formula of weight in pounds and height in inches is in common usage (height and weight charts).
The shortcoming of the BMI is that it does not give an accurate picture of lean mass in relation to adipose tissue. To discriminate between percentages of body fat and lean mass accurately, underwater weighing rather than the commonly used skinfold test must be employed. The arbitrary ranges of 25-29 for overweight and 30 and over for obesity are the standards accepted by the World Health Organization and the National Institutes of Health. Nevertheless, one has only to observe our nation walking down the streets to acknowledge that size matters.
Obesity as a Risk Factor
Obesity is a risk factor for a variety of diseases and has been demonstrated to increase mortality and morbidity:1
Talk to Your Patients: Modifying Obesity Risk Factors
At a given level of overweight or obesity, patients are considered to be at higher risk for health problems and can benefit from weight loss as well as modification of risk factors. Johns Hopkins recommends the following steps to promote patient weight loss:12
In a study of more than 51,000 male health professionals ages 40-75 years, subjects were grouped according to their BMI at age 21. Diabetes risk was positively correlated with absolute weight gain since age 21 as well as with BMI at age 21.6 Abdominal obesity (apple-shaped torso as opposed to pear-shaped), as measured by waist-to-hip ratio, may be a stronger predictor of diabetes than BMI alone. A 1985 study noted that the relative risk of developing diabetes was 30 times higher among those with the highest BMI and waist-to-hip ratio compared with the lowest waist-to-hip ratio.7
Hypertension: The risk of hypertension also increases with increasing BMI. In the Nurses' Health Study, risk of developing hypertension was determined among 41,541 predominantly white female nurses ages 38 to 63 years of age. During a four-year follow-up, the risk of hypertension was increased among overweight and obese women relative to those with a BMI less than 23 kg/m2. The relative risk was 4.8 for those with a BMI of 32 kg/m2 or higher. Weight loss reduced such risk.8
The National Health and Nutrition Examination Surveys (NHANES) data also show that obesity increases risk of hypertension.9 Respondents with a BMI of 30 kg/m2 or greater were twice as likely to have hypertension compared with non-obese subjects. Similarly, subjects with abdominal obesity, defined by waist circumference of at least 102 cm for men and 88 cm for women, were twice as likely to have hypertension.
Heart disease: A relationship between obesity and mortality from heart disease was demonstrated in the Nurses' Health Study. Among women who never smoked, the relative risk of death from heart disease increased significantly with increasing BMI. Women with a BMI of 29 to 31 kg/m2 and 32 kg/m2 or higher were at 4.6 and 5.8 times greater risk, respectively, than those with BMI values under 22 kg/m2. In addition women with the highest waist-to-hip ratio had a greater relative risk of death from cardiac disease compared with those with a lower ratio.10
Gallbladder disease: An independent relationship between obesity and gallbladder disease was shown in the 2002 Atherosclerosis Risk in Communities Study. In women, the risk of hospitalization for gallbladder disease increased with increasing BMI as well as higher waist-to-hip ratio. Overweight women had a 45 percent greater risk of hospitalization for gallbladder disease than those with BMI less than 25 kg/m2. Among obese women, the risk increased further.
In men, the relationship between BMI and the risk of hospitalization for gallbladder disease was only seen among the morbidly obese group. Waist-to-hip ratio did not affect risk among men.
Cancer: A 12-year prospective study followed 750,000 men and women, evaluating the impact of obesity on cancer mortality.11 Men and women who were at least 40 percent overweight were 35 percent and 55 percent more likely, respectively, to die from cancer than those of average weight. Specifically, the mortality ratios for prostate and colorectal cancer (in men), and endometrial, uterine, ovarian, cervical, breast and gallbladder cancer (in women) were highest among those who were at least 40 percent overweight. In the Nurses' Health Study, cancer mortality increased with increasing BMI.10
Osteoarthritis: OA is the most common pathological joint disorder, with symptoms in the hands, knees, hips, back and neck. It is a preventable cause of chronic disability, mostly as a consequence of the effects on the knee. Being only 10 pounds overweight increases the force on the knee by 30-60 pounds with each step. Data from the first Error! Hyperlink reference not valid. indicated that obese women had nearly four times the risk of knee OA as compared with non-obese women; for obese men, the risk was nearly five times greater.12
It has been demonstrated that as weight gain increases, the risk of knee OA increases progressively. Based on the data, it is estimated if all overweight and obese patients reduced their weight by 5 kg or until their weight was with in recommended normal range, 24 percent of surgical cases of knee OA might be avoided.13
All-cause mortality: A study of 750,000 men and women indicated that mortality due to any cause increased with higher body weight.14 In the Nurses' Health Study, all-cause mortality showed a J-shaped relationship between BMI and overall mortality.10 The lowest mortality was found among women with BMI of 19.0 to 26.9 kg/m2, but then mortality increased steadily as BMI levels rose above 27 kg/m2.
Identify and Educate
At the current rate, by 2015, 75 percent of U.S. adults will be overweight and 41 percent will be obese. Obesity has increased at an alarming rate in the United States over the past three decades.3 The causes are multifactorial, but environmental, behavioral and genetic factors all have been shown to contribute.1
Several risk factors for obesity are known, including a sedentary lifestyle, increasing age, and low socioeconomic status. These factors can help doctors to identify which patients are obese or at risk for developing obesity. Elevated BMI and abdominal obesity are associated with a number of diseases that have a high morbidity and mortality. It is important that patients at risk be educated as to the risks and encouraged to change their lifestyle to reduce the risk.
- Pi-Sunyer FX. The obesity epidemic: pathophysiology and consequences of obesity. Obesity Research, 2002;10:97S-104S.
- Finkelstein EA, Ruhm CJ, Kosa KM. Economic causes and consequences of obesity. Public Health, 2005;26:239-57.
- Wang Y. The obesity epidemic in the United States - gender, age, socioeconomic, racial/ethnic and geographical characteristics: a systematic review and meta-regression analysis. Oxford J, 2007:6-28.
- Yach D, Stukler D, Brownell KD. Epidemiological and economic consequences of the global epidemic of obesity and diabetes. Nature Medicine, 2006:12:62-6.
- Colditz GA, Willett WC, Rotnitzky A, Manson JE. Weight gain as a risk factor for clinical diabetes mellitus in women. Ann Int Med, 1995;122:481-6.
- Chan JM, Stampfer MJ, Rimm EB, Willett WC, Colditz GA. Obesity, fat distribution, and weight gain as risk factors for clinical diabetes in men. Diabetes Care, 1994;17:961-9.
- Ohlson LO, Larsson BS, Vardsudd K, et al. The influence of body fat distribution on the incidence of diabetes mellitus. 13.5 years of follow up of the participants in the study of men born in 1913. Diabetes, 1985;34:1055-8.
- Redon J. Hypertension in obesity. Nutr Metab Cardiovasc Dis, 2001;11:344-53.
- Okosun IS, Chandra KMD, Choi S, Christman J, Dever GEA, Prewitt TE. Hypertension and type 2 diabetes comorbidity in adults in the United States: risk of overall and regional adiposity. Obes Res, 2001;9:1-9.
- Manson JE, Willett WC, Stamper MJ, et al. Body weight and mortality among women. N Engl J Med, 1995;333:677-85.
- Garfinkel L. Overweight and cancer. Ann Intern Med, 1985:103:1034-6.
- Johns Hopkins. Role of body weight in osteoarthritis. www.hopkins-arthritis.org/patient –corner/disease management/osteoarthritisweight.html 1/10/2011
- Coggon D, Reading I, Croft P, McLaren M, Barrett D, Cooper C. Knee osteoarthritis and obesity. Int j Obes Relat Metab Disord, 2001;25:622-7
- Lew EA, Garfinkel L. Variations in mortality by weight among 750,000 men and women. J Chronic Dis, 1979;32:563-76.
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