Obesity - a modifiable
risk factor
René Lerch
Cardiology Center, University Hospitals of Geneva, Switzerland
Correspondence: Professor René Lerch, Cardiology
Center, University Hospitals of Geneva, 24 rue Micheli-du-Crest,
1211 Geneva 14, Switzerland. Tel: +41 22 3727193, fax: +41 22
3727229, e-mail: rene.lerch@hcuge.ch
“No!! I am not obese, I am only well developed!”
With these words the corpulent hero Obelix of the popular French
cartoon series angrily refuses to be described as obese. It is
a common experience in daily medical practice that in many obese
patients it is difficult to address this particular risk factor.
However, the growing evidence indicating a causal relationship
between obesity and cardiovascular disease means we can no longer
ignore the issue of excess weight. In 1997 a World Health Organization
(WHO) press release concluded that “Obesity’s impact is so diverse
and extreme that it should now be regarded as one of the greatest
neglected public health problems of our time with an impact on
health which may well prove to be as great as that of smoking”
[1].
Who is obese? From a sociocultural point of view, the answer differs
from country to country and from century to century. For example,
the change in the perception of “corpulence” over the past centuries
is quite apparent from the sensual paintings by the baroque artist
Peter Paul Rubens (1577–1640). From a medical point of view, obesity
has been defined by the WHO as a body mass index (BMI) above 30
kg/m2, whereby BMI is the body weight in kilograms divided by
the square of the height in meters. However, cardiovascular risk
starts to increase well below the threshold of obesity. In a recently
published prospective cohort study including adults of both sexes,
cardiovascular risk began to increase at approximately 25 kg/m2.
[2] Consequently, the WHO defines a BMI of 25
to 29.9 kg/m2 not as normal but as “overweight”. Overweight individuals
have roughly double the risk of fatal or nonfatal heart disease
[3]. Beyond the threshold value of obesity, risk increases
steeply [3]. In the Nurses Health Study each
kilogram of weight gain from the age of 18 years was associated
with a 3.1% higher relative risk of cardiovascular disease
[4]. The increase of risk in obesity is in part explained
by the frequent association of overweight with other risk factors,
including hypertension, dyslipidemia, type 2 diabetes, and enhanced
thrombotic risk. However, multivariate analysis clearly indicates
that after correction for confounding factors, overweight remains
an independent risk factor.
Obesity is a major challenge to modern cardiovascular medicine,
not only because of the enhanced individual risk but also because
of its epidemiological importance. In industrialized countries
15% to 25% of the adult population are obese. According to estimates
by the WHO in the year 2000, there are more than 300 million obese
individuals worldwide. This number is considerably higher than
the 1995 estimate, indicating that we currently face an explosion
of this health problem. Since genetic predisposition does not
change rapidly, environmental factors including eating behavior
and reduced physical activity are likely to play a major role
in the increased prevalence of obesity.
The high incidence of overweight and obesity, the associated cardiovascular
risk, and the metabolic origin of the condition are reason enough
to focus this issue of Heart and Metabolism on obesity. In metabolic
terms, obesity is an imbalance between nutritional energy supply
and energy expenditure. Until recently, little was known of the
feedback loops which ensure whole-body energy homeostasis and
avoid excess proliferation of adipose tissue. During recent years
exciting new observations on the crosstalk between adipose tissue
and the brain have been reported, which are summarized in two
articles in this issue. Randy Seeley and Stephen Woods provide
a concise review of current knowledge on how the brain perceives
adipose tissue mass and translates this information into adaptation
of energy homeostasis. Gema Frühbeck presents the regulatory
mechanisms of energy storage in peripheral tissues. In his clinical
review, Martin Alpert explains how obesity may contribute to increased
cardiovascular morbidity and mortality by a number of mechanisms
which include the development of hypertrophy, leading in some
cases to obesity cardiomyopathy and an enhanced risk of coronary
events. Echocardiography has proven useful to noninvasively monitor
the impact of obesity on cardiac structure and function, as described
by Heribert Schunkert.
Obesity is a modifiable risk factor. Thus far, no controlled clinical
studies have proven the effect of intentional weight loss on longevity
in unselected obese populations. Nevertheless, a reduction in
mortality has been observed in obese patients with diabetes [5].
Furthermore, the benefits of weight reduction on hypertension,
dyslipidemia, and diabetes are well documented and provide a strong
incentive to treat obesity.
Decreasing caloric intake and increasing physical activity remain
the fundamentals of obesity treatment. Unfortunately, the success
rate of weight reduction and maintenance of normal weight is often
unsatisfactory. Taking care of obese patients is a major challenge
that requires a multidisciplinary approach. In selected patients
new therapeutic strategies must be considered, as discussed by
Maria Collazo-Clavell in her article.
REFERENCES
1. Obesity epidemic puts millions at risk from
related diseases [press release]. Geneva: World Health Organization;
June 12, 1997. No. 46.
Comment in:
Body-mass index and mortality in a prospective
cohort of U.S. adults.
Calle EE, Thun MJ, Petrelli JM, Rodriguez C, Heath CW Jr.
Department of Epidemiology and Surveillance Research, American
Cancer Society, Atlanta, GA 30329, USA.
BACKGROUND: Body-mass index (the weight in kilograms divided by the
square of the height in meters) is known to be associated with
overall mortality. We investigated the effects of age, race, sex,
smoking status, and history of disease on the relation between
body-mass index and mortality. METHODS: In a prospective study of
more than 1 million adults in the United States (457,785 men and
588,369 women), 201,622 deaths occurred during 14 years of
follow-up. We examined the relation between body-mass index and the
risk of death from all causes in four subgroups categorized
according to smoking status and history of disease. In healthy
people who had never smoked, we further examined whether the
relation varied according to race, cause of death, or age. The
relative risk was used to assess the relation between mortality and
body-mass index. RESULTS: The association between body-mass index
and the risk of death was substantially modified by smoking status
and the presence of disease. In healthy people who had never smoked,
the nadir of the curve for body-mass index and mortality was found
at a body-mass index of 23.5 to 24.9 in men and 22.0 to 23.4 in
women. Among subjects with the highest body-mass indexes, white men
and women had a relative risk of death of 2.58 and 2.00,
respectively, as compared with those with a body-mass index of 23.5
to 24.9. Black men and women with the highest body-mass indexes had
much lower risks of death (1.35 and 1.21), which did not differ
significantly from 1.00. A high body-mass index was most predictive
of death from cardiovascular disease, especially in men (relative
risk, 2.90; 95 percent confidence interval, 2.37 to 3.56). Heavier
men and women in all age groups had an increased risk of death.
CONCLUSIONS: The risk of death from all causes, cardiovascular
disease, cancer, or other diseases increases throughout the range of
moderate and severe overweight for both men and women in all age
groups. The risk associated with a high body-mass index is greater
for whites than for blacks.
PMID: 10511607 [PubMed - indexed for MEDLINE]
Body size and fat distribution as predictors of
coronary heart disease among middle-aged and older US men.
Rimm EB, Stampfer MJ, Giovannucci E, Ascherio A, Spiegelman D,
Colditz GA, Willett WC.
Department of Epidemiology, Harvard School of Public Health, Boston,
MA 02115, USA.
Obesity, android fat distribution, and other anthropometric measures
have been associated with coronary heart disease in long-term
prospective studies. However, fluctuations in weight due to
age-related hormonal changes and changes in lifestyle practices may
bias relative risk estimates over a long follow-up period. The
authors prospectively studied the association between body mass
index (BMI) (kg/m2), waist-to-hip ratio, and height as independent
predictors of incident coronary heart disease in a 3-year
prospective study among 29,122 US men aged 40-75 years in 1986. The
authors documented 420 incident coronary events during the follow-up
period. Body mass index, waist-to-hip ratio, short stature, and
weight gain since age 21 were associated with an increased risk of
coronary heart disease. Among men younger than 65, after adjusting
for other coronary risk factors, the relative risk was 1.72 (95%
confidence interval (CI) 1.10-2.69) for men with BMI of 25-28.9,
2.61 (95% CI 1.54-4.42) for BMI of 29.0-32.9, and 3.44 (95% CI
1.67-7.09) for obese men with BMI > or = 33 compared with lean men
with BMI < 23.0. Among men > or = 65 years of age, the association
between BMI and risk of coronary heart disease was much weaker.
However, in this age group, the waist-to-hip ratio was a much
stronger predictor of risk (relative risk = 2.76, 95% CI 1.22-6.23
between extreme quintiles). These results suggest that for younger
men, obesity, independent of fat distribution, is a strong risk
factor for coronary heart disease. For older men, measures of fat
distribution may be better than body mass index at predicting risk
of coronary disease.
PMID: 7771450 [PubMed - indexed for MEDLINE]
Comment in:
Body weight and mortality among women.
Manson JE, Willett WC, Stampfer MJ, Colditz GA, Hunter DJ,
Hankinson SE, Hennekens CH, Speizer FE.
Channing Laboratory, Harvard Medical School, Boston, MA, USA.
BACKGROUND. The relation between body weight and overall mortality
remains controversial despite considerable investigation. METHODS.
We examined the association between body-mass index (defined as the
weight in kilograms divided by the square of the height in meters)
and both overall mortality and mortality from specific causes in a
cohort of 115,195 U.S. women enrolled in the prospective Nurses'
Health Study. These women were 30 to 55 years of age and free of
known cardiovascular disease and cancer in 1976. During 16 years of
follow-up, we documented 4726 deaths, of which 881 were from
cardiovascular disease, 2586 from cancer, and 1259 from other
causes. RESULTS. In analyses adjusted only for age, we observed a
J-shaped relation between body-mass index and overall mortality.
When women who had never smoked were examined separately, no
increase in risk was observed among the leaner women, and a more
direct relation between weight and mortality emerged (P for trend <
0.001). In multivariate analyses of women who had never smoked and
had recently had stable weight, in which the first four years of
follow-up were excluded, the relative risks of death from all causes
for increasing categories of body-mass index were as follows:
body-mass index < 19.0 (the reference category), relative risk =
1.0; 19.0 to 21.9, relative risk = 1.2; 22.0 to 24.9, relative risk
= 1.2; 25.0 to 26.9, relative risk = 1.3; 27.0 to 28.9, relative
risk = 1.6; 29.0 to 31.9, relative risk = 2.1; and > or = 32.0,
relative risk = 2.2 (P for trend < 0.001). Among women with a
body-mass index of 32.0 or higher who had never smoked, the relative
risk of death from cardiovascular disease was 4.1 (95 percent
confidence interval, 2.1 to 7.7), and that of death from cancer was
2.1 (95 percent confidence interval, 1.4 to 3.2), as compared with
the risk among women with a body-mass index below 19.0. A weight
gain of 10 kg (22 lb) or more since the age of 18 was associated
with increased mortality in middle adulthood. CONCLUSIONS. Body
weight and mortality from all causes were directly related among
these middle-aged women. Lean women did not have excess mortality.
The lowest mortality rate was observed among women who weighed at
least 15 percent less than the U.S. average for women of similar age
and among those whose weight had been stable since early adulthood.
PMID: 7637744 [PubMed - indexed for MEDLINE]
Comment in:
Intentional weight loss and mortality among
overweight individuals with diabetes.
Williamson DF, Thompson TJ, Thun M, Flanders D, Pamuk E, Byers T.
Division of Diabetes Translation, Centers for Disease Control and
Prevention, Atlanta, Georgia 30341-3717, USA. drw1@cdc.gov
OBJECTIVE: To estimate the effect of intentional weight loss on
mortality in overweight individuals with diabetes. RESEARCH DESIGN
AND METHODS: We performed a prospective analysis with a 12-year
mortality follow-up (1959-1972) of 4,970 overweight individuals with
diabetes, 40-64 years of age, who were enrolled in the American
Cancer Society's Cancer Prevention Study I. Rate ratios (RRs) were
calculated, comparing overall death rates, and death from
cardiovascular disease (CVD) or diabetes in individuals with and
without reported intentional weight loss. RESULTS: Intentional
weight loss was reported by 34% of the cohort. After adjustment for
initial BMI, sociodemographic factors, health status, and physical
activity, intentional weight loss was associated with a 25%
reduction in total mortality (RR = 0.75; 95% CI 0.67-0.84), and a
28% reduction in CVD and diabetes mortality (RR = 0.72; 0.63-0.82).
Intentional weight loss of 20-29 lb was associated with the largest
reductions in mortality (approximately 33%). Weight loss >70 lb was
associated with small increases in mortality CONCLUSIONS:
Intentional weight loss was associated with substantial reductions
in mortality in this observational study of overweight individuals
with diabetes.
Publication Types:
PMID: 11023143 [PubMed - indexed for MEDLINE]
|
