124 Obesity
Nutrition Examination Surveys I, II, III (NHANES I-III;
Flegal et al., 1998; Kuczmarski et al., 1994) allow a com-
prehensive examination of the changing rates of overweight
and obesity over the past four decades. NHES evaluated
data collected from 1960 to 1962 and reported an over-
weight prevalence of 43.3% in adults. Nearly a decade later,
the data from NHANES I, conducted in 1971 to 1974,
indicated an overall prevalence of 46.1%, a level which re-
mained relatively constant during the next decade, as re-
”ected in the 46.0% prevalence observed in NHANES II,
conducted in 1976 to 1980. However, the results of
NHANES III, conducted in 1988 to 1994, revealed an
alarming increase in the prevalence of overweight individu-
als to 54.9%. Particularly disturbing were the rates of obe-
sity (BMI 30), which increased 10% among women and
8% among men during the 14 years between NHANES II-
III (Leigh, Fries, & Hubert, 1992). Figure 6.2 presents the
prevalence rates of obesity from the four population surveys
conducted between 1960 and 1994.
CONSEQUENCES OF OBESITY
Impact on Morbidity
Obesity has a substantial adverse impact on health via its as-
sociation with a number of serious illnesses and risk factors
for disease. Obesity-related conditions include hypertension,
dyslipidemia, type 2 diabetes mellitus, coronary heart disease
(CHD), stroke, gallbladder disease, osteoarthritis, sleep
apnea, respiratory problems, and cancers of the endometrium,
breast, prostate and colon.
Some of the more prominent comorbidities of obesity are
described next.Hypertension.The prevalence of high blood pressure
in adults is twice as high for individuals with BMI 30
than for those with normal weight (Dyer & Elliott, 1989;
Pi-Sunyer, 1999). Mechanisms for increased blood pres-
sure appear to be related to increases in blood volume,
vascular resistance, and cardiac output. Hypertension is
a risk factor for both CHD and stroke (Havlik, Hubert,
Fabsitz, & Feinleib, 1983).
Dyslipidemia.Obesity is associated with lipid pro-
“les that increase risk for CHD, including elevated levels
of total cholesterol, triglycerides, and low-density lipopro-
tein (•badŽ) cholesterol, as well as low levels of high-
density lipoprotein (•goodŽ) cholesterol (Allison &
Saunders, 2000).
Type 2 Diabetes Mellitus.Data from international studies
consistently show that obesity is a robust predictor of the
development of diabetes (Folsom et al., 2000; Hodge,
Dowse, Zimmet, & Collins, 1995; NHLBI, 1998). A 14-
year prospective study concluded that obese women were at
40 times greater risk for developing diabetes than normal-
weight, age-matched counterparts (Colditz et al., 1990).
Current estimates suggest that 27% of new cases of type 2
diabetes are attributable to weight gain of 5 kg or more in
adulthood (Ford, Williamson, & Liu, 1997). Moreover, ab-
dominal obesity is a speci“c major risk factor for type 2 dia-
betes (Chan, Rimm, Colditz, Stampfer, & Willett, 1994).
Coronary Heart Disease.Overweight, obesity, and ab-
dominal adiposity are associated with increased morbidity
and mortality due to CHD. These conditions are directly
related to elevated levels of cholesterol, blood pressure,
and insulin, all of which are speci“c risk factors for car-
diovascular disease. Recent studies suggest that, com-
pared to a BMI in the normal range, the relative risk for
CHD is twice as high at a BMI of 25 to 29, and three times
as high for BMI 29 (Willett et al., 1995). Moreover, a
weight gain of 5 to 8 kg increases CHD risk by 25%
(NHLBI, 1998; Willett et al., 1995).
Stroke.The Framingham Heart Study (Hubert, Feinleib,
McNamara, & Castelli, 1983) suggested that overweight
may contribute to stroke risk, independent of hypertension
and diabetes. Later research established that the relation-
ship between obesity and stroke is clearer for ischemic
stroke versus hemorrhagic stroke (Rexrode et al., 1997).
Recent prospective studies show a graduated increase in
risk for ischemic stroke with increasing BMI (i.e., risk isFigure 6.2 Prevalence of obesity (BMI 30) in United States. Source:
Data from NHANES I, II, and III; Flegal et al., 1998.
NHES I (1960–1962)
NHANES I (1971–1974)
NHANES II (1976–1980)
NHANES III (1988–1994)PercentMen Women