Manual of Clinical Nutrition Management III- 81 Copyright © 2013 Compass Group, Inc.
OBESITY AND WEIGHT MANAGEMENT
Discussion
Recent data indicate that 64% of American adults are either overweight (body mass index [BMI] of 25.0 to
29.9 kg/m^2 ) or obese (BMI >30 kg/m^2 ) (1). This figure has sharply increased since 1994 when 55% of
American adults were overweight or obese. The rate of obesity has doubled from 15% in 1980 to 30% in
1999 (1,2). The trend is similar in American children and adolescents. The 1999 to 2000 National Health and
Nutrition Examination Survey (NHANES) identified the prevalence of overweight as 15.5% among 12-
through 19-year-olds; 15.3% among 6- through 11-year-olds; and 10.4% among 2- through 5-year-olds.
These percentages are greater than the corresponding values of 10.5%, 11.3%, and 7.2% in 1988 to 1994
(NHANES III) (2). Overweight children have a greater risk for becoming overweight adults (3). Obesity
contributes to many adverse health outcomes, including type 2 diabetes, cardiovascular disease,
hypertension, stroke, osteoarthritis, gallbladder disease, sleep apnea, respiratory problems, and cancers of
the endometrium, breast, prostate, and colon (1,4). The total estimated cost of obesity in 1995 was $99.2
billion, which includes $51.6 billion spent on direct medical costs (5).
Obesity is a complex multifactorial disease that results from the positive energy balance that occurs when
energy intake exceeds energy expenditure. Lifestyle and environmental factors, including excessive energy
intake, high fat intake, and physical inactivity, are associated with the pathophysiology of obesity. Growing
evidence suggests a strong link between genetic factors and the pathogenesis of obesity. Genes involved in
energy regulation such as leptin, a signal protein for satiety produced in the adipose tissue, and other
hormones or peptides, such as neuropeptide Y, may have important implications for understanding the
causes of obesity (6). Ongoing research is required to determine the role of genetic factors in obesity
treatment.
Adults
The Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults (4)
provide guidelines for classifying the degree of overweight and obesity and the associated health risk as well
as guidelines for developing treatment strategies. The BMI is used to classify the degree of overweight or
obesity in adults because it is highly correlated with body fatness (4). The BMI is calculated by dividing weight
in kilograms by height in meters squared. Studies have identified a relationship between an elevated BMI
(>25 kg/m^2 ) and an increased incidence of morbidity and mortality (1,4). The BMI and waist circumference
should be used to classify overweight and obesity, estimate risk for disease, and identify treatment options
(Grade II) *(4,7). (Refer to Table III- 22 .) The BMI and waist circumference are highly correlated to obesity or fat
mass and risk of other diseases (Grade II) (4,7). Waist circumference is also used as an assessment parameter
because excess fat in the abdomen is an independent predictor of increased risk and morbidity, even for
individuals with a normal weight (4). Evidence from epidemiologic studies shows waist circumference to be a
better marker of abdominal fat than the waist-to-hip ratio. Waist circumference also is the most practical
anthropometric measurement for assessing a patient’s abdominal fat content before and during weight loss
treatment (4). A high waist circumference is associated with increased risk for type 2 diabetes, dyslipidemia,
hypertension, and cardiovascular disease in patients whose BMI is between 25.0 and 34.9 kg/m^2. However,
for individuals whose BMI is greater than 35.0 kg/m^2 , waist circumference adds little to the predictive power
of the disease risk classification of BMI (4). (Refer to Table III- 23 )