Monday, June 22, 2009
Obesity is of public health concern because of its association with serious medical complications that lead to increased morbidity and mortality. Being overweight is a problem in the United States. A third of all adult Americans are overweight.
If you are overweight, you are at high risk for obesity. And even if you don’t become obese, you are at a higher risk than a person with a healthy weight.
The most common complications associated with obesity are insulin resistance, diabetes mellitus, hypertension, dyslipidemia, cardiovascular disease, gallstones and cholecystitis, respiratory dysfunction, and increased incidence of certain cancers.
DIABETES MELLITUS
There is a strong positive correlation between the average weight in a population and the presence of type 2 (non-insulin-dependent) diabetes mellitus. In a male population divided into groups with BMIs of 25.0 to 26.9, 29 to 30, and greater than 35, the risk for diabetes (compared to a population with BMIs less than 21) increases 2.2-, 6.7-, and 42- fold, respectively.
The severity of the obesity is a determinant, as is the length of time obesity has been present. The pathogenesis of the diabetes is related to the insulin resistance caused by the obesity, which tends to increase in severity as BMI rises.
HYPERTENSION
About one-third of all obese persons are hypertensive. Epidemiological studies have demonstrated that for every 10-kilogram rise in body weight over normal, there is an average increase of 3 mm Hg in systolic and 2 mm Hg in diastolic pressure.
The longer the duration of obesity, the greater the risk of developing hypertension. Using data from the U.S. National Health Examination II Survey (in which obesity was defined as a weight for height above the 85th percentile of that of men and women in the third decade of life), the prevalence of hypertension in persons 20% or more overweight was twice that of persons of normal weight.
STROKE
Directly linked to the increased prevalence of hypertension in obese persons is an increased risk of stroke. In the Framingham Heart Study, for instance, there was a steeply rising curve of stroke with increasing weight.
For example, in the male group under 50 years of age, the risk of stroke rose from 22 to 30 to 49 per thousand as relative weights rose from 110% to 129% to higher than 130%, respectively.
DYSLIPIDEMIA
Obesity is associated with three particular abnormalities of circulating lipids:
1. Elevation of triglyceride levels,
2, Depression of high-density lipoprotein cholesterol (HDL-C) levels, and
3. Increased presence of small, dense low-density lipoprotein (LDL) particles.
CARDIOVASCULAR DISEASE
Coronary heart disease is usually described epidemiologically as cardiovascular disease (CVD), which includes angina pectoris, nonfatal myocardial infarction, and sudden death. These conditions occur more frequently in obese persons.
GALLBLADDER DISEASE
A number of changes that occur with obesity predispose an individual to gallstone formation. As cholesterol excretion from the liver increases, the bile becomes supersaturated with cholesterol.
Also, the motility of the gallbladder decreases, so that the sac is emptied much less efficiently. Whether this condition is due to a decreased sensitivity to the cholecystokinin released with each meal is unclear. The net effect is to increase the formation of predominantly cholesterol-containing stones.
These stones enhance the propensity to gallbladder inflammation, so that acute and chronic cholecystitis is much more common in obese persons. The incidence of this condition is higher in women than in men, partly because the prevalence of obesity is higher in women, but there may be other, as yet undiscovered reasons.
The need for surgery to remove diseased gallbladders is much more common in obese persons, and more so in women than in men.
RESPIRATORY DISEASE
The increased weight of the chest in obese persons leads to poor respiratory motion and also decreased compliance of the respiratory system, so that both vital capacity and total lung capacity are often low.
As the overweight becomes more severe, ventilation–perfusion abnormalities impair adequate oxygenation of the blood, even though carbon dioxide escape is adequate. With continued and persistent obesity, sleep apnea, either peripheral or central, may occur. Peripheral apnea is manifested by obstruction of the airway, caused by excess fatty tissue and the relaxation of the pharyngeal and glossal muscles. Central apnea is the result of a cessation of the signals that initiate inspiration.
The mechanism for this cessation of signals is unclear but apneic episodes may occur many times during the night, causing significant hyperventilation. The severity of all these abnormalities may lead to progressively more severe hypoxemia and hypercapnia, which in turn may lead to pulmonary hypertension, right heart failure, and cor pulmonale.
CANCER
The relationships of obesity to various forms of cancer are somewhat unclear, and more data are required. However, there is an association between some cancers and overweight.
It is not known whether the association may be due to other relationships, such
as a high-fat diet, elevated total calories, or other specific dietary components. However, the associations, leaving causality unclear, have been well described.
In women, higher rates have been described for endometrial, gallbladder, cervical, and ovarian cancers. For breast cancer, premenopausal women who are obese are less at risk, while postmenopausal women are at greater risk. It is possible that some of this postmenopausal effect on breast cancer is related to the increasing estrogenicity that occurs with increasing obesity as women age. This increased estrogenicity is the result of estrogen production in adipose tissue from sex hormone precursors that are soluble in fat and converted there to active estrogen. This combined estrogenicity might affect breast cancer incidence. An increased incidence of colorectal and prostate cancers has been found in obese men. The mechanisms of this effect are unknown, although recent evidence suggests that the increased insulin levels resulting from the insulin resistance of
obesity may have mitogenic effects.
ARTHRITIS AND GOUT
Because of the increased stress on the weight-bearing joints caused by increased weight, degenerative disease of these joints is quite common in obese persons, particularly as the duration and severity of the obesity increases.
There is also an increased incidence of gout in persons who are overweight. Such an association has been found repeatedly in cross-sectional studies. This association of gout and overweight is manifested to a much greater degree in men than in women, in whom higher levels of excess fat are needed for the disease to develop.
EFFECTS OF FAT DISTRIBUTION
Epidemiological data from many countries have established fat distribution as an important determinant of disease risk. As a result, not only the degree of obesity but also the location of deposited fat are important. Results of available studies suggest that intra-abdominal, or visceral, fat is crucial in this regard. The pathophysiology may be related to the increased lipolytic activity of fat cells in this region, which release large amounts of FFA to the liver and the periphery. The combination of hyperlipacidemia and hyperinsulinemia leads to increased VLDL production, with resultant hypertriglyceridemia. The lipacidemia also inhibits glucose transport and oxidation in muscle, increasing the insulin resistance and the propensity for diabetes. The hyperinsulinemia leads to increased sodium absorption and increases the risk of hypertension.
The medical complications of obesity are considerable. It must be realized that diabetes mellitus, hypertension, dyslipidemia, cardiovascular disease, and stroke—aside from cancer, AIDS, and violence—are the leading causes of morbidity and mortality in the developed world. If cancer, a condition in which obesity often plays a part, is added, obesity is a large contributor to the burden of disease affecting industrialized countries.
Whether the effect of these diseases is direct and independent or indirect, through enhancing other risk factors, is essentially irrelevant from a public health perspective. If obesity could be prevented, a very significant and positive impact on chronic disease and mortality would occur.
Based on book : EATING DISORDERS AND OBESITY Edited by Christopher G. Fairburn and Kelly D. Brownell
This posting about medical consequences for childhood with obesity
If you are overweight, you are at high risk for obesity. And even if you don’t become obese, you are at a higher risk than a person with a healthy weight.
The most common complications associated with obesity are insulin resistance, diabetes mellitus, hypertension, dyslipidemia, cardiovascular disease, gallstones and cholecystitis, respiratory dysfunction, and increased incidence of certain cancers.
DIABETES MELLITUS
There is a strong positive correlation between the average weight in a population and the presence of type 2 (non-insulin-dependent) diabetes mellitus. In a male population divided into groups with BMIs of 25.0 to 26.9, 29 to 30, and greater than 35, the risk for diabetes (compared to a population with BMIs less than 21) increases 2.2-, 6.7-, and 42- fold, respectively.
The severity of the obesity is a determinant, as is the length of time obesity has been present. The pathogenesis of the diabetes is related to the insulin resistance caused by the obesity, which tends to increase in severity as BMI rises.
HYPERTENSION
About one-third of all obese persons are hypertensive. Epidemiological studies have demonstrated that for every 10-kilogram rise in body weight over normal, there is an average increase of 3 mm Hg in systolic and 2 mm Hg in diastolic pressure.
The longer the duration of obesity, the greater the risk of developing hypertension. Using data from the U.S. National Health Examination II Survey (in which obesity was defined as a weight for height above the 85th percentile of that of men and women in the third decade of life), the prevalence of hypertension in persons 20% or more overweight was twice that of persons of normal weight.
STROKE
Directly linked to the increased prevalence of hypertension in obese persons is an increased risk of stroke. In the Framingham Heart Study, for instance, there was a steeply rising curve of stroke with increasing weight.
For example, in the male group under 50 years of age, the risk of stroke rose from 22 to 30 to 49 per thousand as relative weights rose from 110% to 129% to higher than 130%, respectively.
DYSLIPIDEMIA
Obesity is associated with three particular abnormalities of circulating lipids:
1. Elevation of triglyceride levels,
2, Depression of high-density lipoprotein cholesterol (HDL-C) levels, and
3. Increased presence of small, dense low-density lipoprotein (LDL) particles.
CARDIOVASCULAR DISEASE
Coronary heart disease is usually described epidemiologically as cardiovascular disease (CVD), which includes angina pectoris, nonfatal myocardial infarction, and sudden death. These conditions occur more frequently in obese persons.
GALLBLADDER DISEASE
A number of changes that occur with obesity predispose an individual to gallstone formation. As cholesterol excretion from the liver increases, the bile becomes supersaturated with cholesterol.
Also, the motility of the gallbladder decreases, so that the sac is emptied much less efficiently. Whether this condition is due to a decreased sensitivity to the cholecystokinin released with each meal is unclear. The net effect is to increase the formation of predominantly cholesterol-containing stones.
These stones enhance the propensity to gallbladder inflammation, so that acute and chronic cholecystitis is much more common in obese persons. The incidence of this condition is higher in women than in men, partly because the prevalence of obesity is higher in women, but there may be other, as yet undiscovered reasons.
The need for surgery to remove diseased gallbladders is much more common in obese persons, and more so in women than in men.
RESPIRATORY DISEASE
The increased weight of the chest in obese persons leads to poor respiratory motion and also decreased compliance of the respiratory system, so that both vital capacity and total lung capacity are often low.
As the overweight becomes more severe, ventilation–perfusion abnormalities impair adequate oxygenation of the blood, even though carbon dioxide escape is adequate. With continued and persistent obesity, sleep apnea, either peripheral or central, may occur. Peripheral apnea is manifested by obstruction of the airway, caused by excess fatty tissue and the relaxation of the pharyngeal and glossal muscles. Central apnea is the result of a cessation of the signals that initiate inspiration.
The mechanism for this cessation of signals is unclear but apneic episodes may occur many times during the night, causing significant hyperventilation. The severity of all these abnormalities may lead to progressively more severe hypoxemia and hypercapnia, which in turn may lead to pulmonary hypertension, right heart failure, and cor pulmonale.
CANCER
The relationships of obesity to various forms of cancer are somewhat unclear, and more data are required. However, there is an association between some cancers and overweight.
It is not known whether the association may be due to other relationships, such
as a high-fat diet, elevated total calories, or other specific dietary components. However, the associations, leaving causality unclear, have been well described.
In women, higher rates have been described for endometrial, gallbladder, cervical, and ovarian cancers. For breast cancer, premenopausal women who are obese are less at risk, while postmenopausal women are at greater risk. It is possible that some of this postmenopausal effect on breast cancer is related to the increasing estrogenicity that occurs with increasing obesity as women age. This increased estrogenicity is the result of estrogen production in adipose tissue from sex hormone precursors that are soluble in fat and converted there to active estrogen. This combined estrogenicity might affect breast cancer incidence. An increased incidence of colorectal and prostate cancers has been found in obese men. The mechanisms of this effect are unknown, although recent evidence suggests that the increased insulin levels resulting from the insulin resistance of
obesity may have mitogenic effects.
ARTHRITIS AND GOUT
Because of the increased stress on the weight-bearing joints caused by increased weight, degenerative disease of these joints is quite common in obese persons, particularly as the duration and severity of the obesity increases.
There is also an increased incidence of gout in persons who are overweight. Such an association has been found repeatedly in cross-sectional studies. This association of gout and overweight is manifested to a much greater degree in men than in women, in whom higher levels of excess fat are needed for the disease to develop.
EFFECTS OF FAT DISTRIBUTION
Epidemiological data from many countries have established fat distribution as an important determinant of disease risk. As a result, not only the degree of obesity but also the location of deposited fat are important. Results of available studies suggest that intra-abdominal, or visceral, fat is crucial in this regard. The pathophysiology may be related to the increased lipolytic activity of fat cells in this region, which release large amounts of FFA to the liver and the periphery. The combination of hyperlipacidemia and hyperinsulinemia leads to increased VLDL production, with resultant hypertriglyceridemia. The lipacidemia also inhibits glucose transport and oxidation in muscle, increasing the insulin resistance and the propensity for diabetes. The hyperinsulinemia leads to increased sodium absorption and increases the risk of hypertension.
The medical complications of obesity are considerable. It must be realized that diabetes mellitus, hypertension, dyslipidemia, cardiovascular disease, and stroke—aside from cancer, AIDS, and violence—are the leading causes of morbidity and mortality in the developed world. If cancer, a condition in which obesity often plays a part, is added, obesity is a large contributor to the burden of disease affecting industrialized countries.
Whether the effect of these diseases is direct and independent or indirect, through enhancing other risk factors, is essentially irrelevant from a public health perspective. If obesity could be prevented, a very significant and positive impact on chronic disease and mortality would occur.
Based on book : EATING DISORDERS AND OBESITY Edited by Christopher G. Fairburn and Kelly D. Brownell
This posting about medical consequences for childhood with obesity
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