Affluence, Food Excess, And Nutritional Disorders
Nutrition research in the first half of the present century
focused mainly on identifying and assessing nutrients in foods and recognizing
deficiency diseases. Since essential nutrients were unevenly distributed in
individual foods, consumption of a variety of foods was recommended to provide
a more nutritionally balanced diet.
With undernutrition still a problem even in the richer
countries, greater consumption of meat and dairy products was recommended. Increasing
wealth in society allowed these recommendations to match producer and consumer
wishes and acknowledged, at the same time, the perceived high nutritional
values of these foods of animal origin.
By the 1950s, however, evidence was accumulating that the
high rates of premature deaths from some of the major chronic diseases could be
related to diet. Originally this was thought to be a problem only in the
industrialized countries but, as medicine conquered infectious diseases, the
phenomenon became recognized as existing worldwide.
OBESITY
Obesity affects many millions of Americans and is a major
public health problem. It is characterized by excess body fat caused by an
imbalance between energy intake and energy expenditure. The specific reasons
behind such an imbalance, however, remain the subject of much debate.
Genetic, environmental and behavioral variables all
influence the risk of becoming overweight, but the relative importance of each
remains unclear. The prevalence of obesity for different age groups in the
United States is shown in Table 1.
Direct assessment of body fat can be used to evaluate
obesity but the procedure is mainly limited to research. For public health
studies and clinical practice, simple measures such as height and weight
tables, body mass index (BMI), or skinfold measurements are used. The BMI
(weight in kilograms divided by the square of height in meters) is an indicator
that shows the best correlation with independent measures of body fat.
The use of BMI was first proposed in 1871 and was long known
as the Quetelet index. It is now widely used for assessing the degree of
obesity or overweight (Table 2). Obesity is more than a problem in its own
right since it is closely linked to other diseases such as hypertension,
diabetes, and cardiovascular disease.
Many long-term studies have shown a greater risk of these
diseases with increasing levels of obesity, even when other risk factors are
present. Later studies have refined these conclusions and have demonstrated
that the distribution of fat, especially in the abdominal area, is an
additional factor.
A waist circumference of over 40 in. (102 cm) in men and
over 35 in. (89 cm) in women signifies increased risk in those who have a BMI
of 25.0 to 34.9. With increasing BMI, average blood pressure and total
cholesterol levels rise while average high-density lipoprotein (HDL—a protective
indicator) levels fall. Men in the highest obesity category have more than
twice the risk of hypertension and elevated cholesterol when compared with men
of normal weight.
Women in the highest obesity category have four times the
risk of either or both of these risk factors. Obese individuals are also at
increased risk for several other problems, including lipid disorders, type II
diabetes, coronary heart disease, stroke, gallbladder disease, osteoarthritis,
sleep apnea, respiratory problems, and certain cancers. A number of efforts
have been initiated to educate the public on altering behavioral risk factors
such as improper dietary habits and lack of exercise.
Examples include the Dietary Guidelines for Americans (Table
3), revised editions of which are periodically issued by the U.S. Department of
Agriculture (USDA). Recently the first federal guidelines on the
identification, evaluation, and treatment of overweight and obesity in adults
were released. These clinical practice guidelines are designed to help
physicians in their care of overweight and obesity and include the scientific
background for assessment as well as the principles of safe and effective
weight loss.
Three key indicators are recommended BMI, waist
circumference, and the patient's risk factors for diseases and conditions
associated with obesity. Overweight is defined as a BMI of 25.0 to 29.9 while
obesity is a BMI greater than 30.0. These values are consistent with the
definitions used in many other countries and support the Dietary Guidelines for
Americans.
A BMI of 30.0, for example, a weight of 221 Ib for a 6-ft
person (100 kg: 1.83 m) or 186 Ib for a person of 5 ft, 6 in. (84 kg: 1.68 m)
indicates about 30 Ib (13.6 kg) overweight for both men and women. Highly
muscular people may have a high BMI without increased health risks. For the
majority, however, BMI is an excellent indicator of overall risk. The most
successful strategies for weight loss include reduction of food energy intake,
increased physical activity, and behavior therapy designed to improve eating
and physical activity habits. Other recommendations are listed in Table 4.
One in five children in the United States is now overweight.
Care and treatment differ from adults, and therefore pediatric guidelines have
been proposed by an expert committee. Clinicians who care for these children
and their families are urged not to express blame but to show
"sensitivity, compassion and a conviction that obesity is an important
chronic medical condition that can be treated." Balanced nutritional
intakes with avoidance of excess together with adequate physical activity are
important goals for all family members.
Table 1. Prevalence of Overweight, Severe Overweight, and Morbid Obesity (NHANES II)
|
|
Males |
Females |
Total Millions |
||
|
Millions |
Prevalence % |
Millions |
Prevalence % |
||
|
Overweight |
15.4 |
24.2 |
18.6 |
27.1 |
34.0 |
|
Severe overweight |
5.1 |
8.0 |
7.4 |
10.6 |
12.5 |
|
Morbid obesity |
0.327 |
0.6 |
1.7 |
2.5 |
2.0 |
Table 2. Classification of Overweight and Obesity Based on
Body Mass Index
|
Degree of Obesity |
BMP |
|
Grade III (morbid obesity) |
>40 |
|
Grade II (obese) |
30-39.9 |
|
Grade I (overweight) |
25-29.9 |
|
Grade 0 (normal) |
20-24.9 |
BMI = weight in kilograms divided by the square of the
height in meters.
Table 3. Dietary Guidelines for Americans
|
Eat a variety of foods. |
|
Balance the food you eat with physical activity; maintain
or improve your weight. |
|
Choose a diet with plenty of grain products, vegetables,
and fruits • Choose a diet low in fat, saturated fat, and cholesterol. |
|
Choose a diet moderate in sugars. |
|
Choose a diet moderate in salt and sodium. |
|
If you drink alcoholic beverages, do so in moderation. |
HYPERTENSION
In the adult, hypertension (high blood pressure) is defined
as a pressure greater than, or equal to, 140 mmHg systolic, or greater than or
equal to, 90 mmHg diastolic pressure. In 90 to 95% of the cases of high blood
pressure, the specific cause may be unknown. Hypertension is a risk factor for
both coronary heart disease and stroke.
Although it can occur in children and adolescents, it is
more prevalent in the middle-aged and elderly, especially African, Americans
and the obese. Heavy drinkers and women who are taking oral contraceptives are
also at increased risk. Individuals with diabetes mellitus, gout, or kidney
disease also have a higher frequency of hypertension.
Salt consumption can increase blood pressure for some. High
blood pressure is related to obesity and to increases in body weight over time
(9,12). Factors increasing the risk of developing high blood pressure are
listed in Table 5. Weight loss, an active lifestyle, reduction in sodium
intake, and moderation of alcohol consumption are recommended for prevention
and management. For many, however, medical intervention with antihypertensive
drugs is required to maintain acceptable blood pressure.
Table 4. Selected Recommendations from the First Federal Obesity Guidelines Panel
|
Engage in moderate physical activity (30 min or more) on
most/all days of the week. |
|
Reduce dietary fat and calories. Cutting back on dietary
fat can help reduce calories and is heart-healthy. |
|
The initial goal of treatment should be to reduce body
weight by about 10% from baseline, an amount that reduces obesityrelated risk
factors. With success, and if warranted, further weight loss can be
attempted. |
|
A reasonable time line for a 10% reduction in body weight
is six months of treatment (weight loss of 1 to 2 Ib per week). |
|
Weight maintenance should be a priority after the first 6
months of weight-loss therapy. |
|
Overweight and obese patients who do not wish to lose
weight, or are otherwise not candidates for weight-loss treatment, should be
counseled on strategies to avoid further weight gain. |
|
Age alone should not preclude weight-loss treatment in
older adults. A careful evaluation of potential risks and benefits in the
individual patient should guide management. |
Table 5. Risk Factors for Hypertension (High Blood Pressure)
|
Heredity |
|
Male gender |
|
Sodium or salt sensitivity |
|
Heavy alcohol consumption |
|
Sedentary and inactive lifestyle |
|
Race (African Americans are at greater risk) |
|
Age |
|
Obesity and overweight |
|
Use of oral contraceptives and some other medications |
DIABETES MELLITUS
What can now be recognized as diabetes was described in the
ancient civilizations of Egypt, Greece, and India. The sweet taste of urine in
those with the condition was noted in the 1600s and the term
"mellitus" meaning honeylike was introduced. Diabetes mellitus is a
major public health problem worldwide.
It ranks sixth as a primary cause of death in the United
States, but when its complications are included, it ranks third. These
complications can be very serious and involve, in the United States, 50% of the
amputations of all lower extremities in adults and 25% of all kidney failure
and are also a leading cause of blindness. Non-insulin-dependent diabetes
(NIDDM, or type II) is the form of diabetes characterized as a chronic nutritionally
related condition (Table 6) and is a disorder showing abnormalities in glucose,
fat, and protein metabolism.
The onset of type II diabetes can be triggered by dietary
and lifestyle factors similar to those associated with cardiovascular diseases.
Diabetes and heart disease in later life appear to be linked to weight at birth.
CARDIOVASCULAR DISEASE
Cardiovascular disease (CVD) has been for many years the
leading single cause of death in the United States: it includes both coronary
heart disease (CHD) and stroke. CHD is the most common form of cardiovascular
disease. In 1987 nearly 1 million deaths in the United States, half of the
total number, occurred due to some form of CVD.
In 1998, CVD remains
the leading cause of death in the United States, although there have been some
reductions in the rate. Cardiovascular disease is often thought to affect
mainly men and the elderly, but it is also a major killer of women and people
in the prime of life. An estimated 58 million Americans live with some form of
the disease, and almost 10 million Americans aged 65 years and older report
disabilities caused by heart disease.
Stroke is also a leading cause of disability in the United
States, affecting more than 1 million people nationwide. The health burden of
this condition is rivaled by the economic burden, which has a profound impact
on the health care system. Extensive clinical and epidemiological studies have
identified several major and contributing risk factors of heart disease and
stroke. The major risk factors are listed in Table 7. Some such as increasing
age, male gender, and genetic background cannot be changed, treated, or
modified.
Others, for example, smoking, high serum cholesterol, high
blood pressure, physical inactivity, obesity, and overweight, are under some
control by the individual. Smokers have twice the risk of heart disease
compared with nonsmokers. Nearly one-fifth of all deaths from cardiovascular
diseases (180,000 deaths per year) are attributable to smoking. Surveillance
data indicate that an estimated 1 million young people become regular smokers
each year.
The risk of heart disease increases with a rise in
cholesterol levels especially when other risk factors are present. Plasma total
cholesterol was accepted as a causal factor (among multiple factors) by the
World Health Organization (WHO) expert committee in 1982 and by the U.S.
National Institute of Health Consensus Development Conference in 1985. Diet and
its effects on plasma cholesterol levels are discussed in the next section.
Plasma triglyceride levels have also been correlated with increased risk of
heart disease and are associated with increased low-density lipoprotein (LDL)
cholesterol levels.
High blood pressure increases the risk of a stroke, heart
attack, kidney failure, and congestive heart failure. When obesity, smoking,
high blood cholesterol levels, or diabetes are also present, high blood
pressure increases the risk of a heart attack or stroke severalfold. Regular
moderate-to-vigorous exercise plays a significant role in preventing heart and
blood vessel disease. Exercise helps control blood cholesterol, diabetes, and
obesity as well as maintaining blood pressure.
However, surveys have shown that more than half of American
adults do not practice the recommended level of physical activity. Obese people
are at a greater risk of heart disease, high blood pressure, high cholesterol,
and other chronic diseases and diabetes. Diabetes is also a serious risk factor
for heart disease with more than 80% of diabetics succumbing to some form of heart
or blood vessel disease.
Table 6. Classification of Diabetes Mellitus
|
Spontaneous Diabetes Mellitus (DM) |
|
Insulin-dependent
(IDDM, or type I) |
|
Non-insulin-dependent
(NIDDM or type II) |
|
Nonobese
NIDDM |
|
Obese
NIDDM |
|
Maturity
onset diabetes of young people |
|
Secondary
diabetes |
|
Gestational
diabetes |
Table 7. Major Risk Factors for Cardiovascular Disease
|
Increasing age |
|
Heredity |
|
High blood cholesterol levels |
|
Physical inactivity |
|
Diabetes mellitus |
|
Male gender |
|
Smoking |
|
High blood pressure |
|
Obesity and overweight |
ROLE OF DIET IN CARDIOVASCULAR DISEASE
Improper eating habits accompanied by the lack of exercise
increase the risk of gaining excess weight, a major risk factor for heart
disease, high blood pressure, and diabetes. Diet also affects plasma cholesterol
levels. Cholesterol is carried in the blood associated with two major types of
lipoproteins; LDL and HDL.
LDL cholesterol has been correlated with increased risk of
cardiovascular disease. For many years it has been recognized that dietary
cholesterol has only a limited effect on plasma cholesterol levels. Absorption
of ingested cholesterol is poor, and part of the cholesterol in plasma is
synthesized in the liver. Total lipid intake, and the type of fat consumed,
have more effect in raising plasma cholesterol than does dietary cholesterol.
Saturated fatty acids were found to raise cholesterol, polyunsaturated fatty
acids lowered plasma cholesterol, and monounsaturated fatty acids had an
intermediate effect.
In the classic seven-country prospective study where lipid
intake was correlated with CHD, the disease incidence was also related to the
intake of saturated fat. Most dietary prevention trials have reduced total fat,
saturated fat, and cholesterol intakes along with moderately increased
polyunsaturated fat levels. Similar recommendations are also inclusive in many
of the guidelines for health in the United States.
Recent research indicates that monounsaturated fatty acids
such as oleic acid, which were thought to be neutral, have, in fact, a
substantial cholesterol lowering effect. Trans fatty acids formed during
hydrogenation of certain edible oils may, perhaps, increase LDL cholesterol and
decrease HDL cholesterol. A high fish intake has been associated with
beneficial effects on the prevention of CHD. Fish oils contain DHA
(docosahexaenoic acid), which has a plasma triglyceride-lowering effect.
High levels of dietary carbohydrate, especially complex
carbohydrate, are associated with a decreased risk of cardiovascular disease. A
recent study found rice bran as well as oat bran to have a hypocholesterolemic
effect. Increasing intakes of a number of vitamins have also been shown to be
protective toward cardiovascular disease.
These include vitamins B6, C, E, and folate. Vitamin C and E
are antioxidants and have been hypothesized as preventing damage to coronary
arteries. Elevated serum vitamin C has also been correlated with increased HDL cholesterol
levels in women. Increased consumption of folate and vitamin B6 have also been
shown to reduce risk of CHD in women. Current dietary recommendations (Table 3)
incorporate many of these proven relationships between diet and health.
CANCER
Cancer is a disease condition characterized by excessive
growth of cells due to abnormal multiplication and replication. The biological
process shows several experimentally distinct phases following exposure to a
carcinogen. These include: initiation, tumor promotion, and tumor progression.
After CVD, cancer is the next highest cause of death in the
United States. Many adverse effects that occur in patients are due, not only to
the cancer itself, but also to the treatment. Loss of appetite (anorexia) is
the most common side effect. When advanced and persistent, this along with
other metabolic and physiologic changes can eventually lead to severe
undernutrition termed cancer cachexia.
Anorexia is not unique to cancer; however, it is persistent
and severe in certain cancers such as the carcinoma of the stomach, breast, and
large bowel. Onset of anorexia is insidious and may not be accompanied by any
obvious manifestations other than progressive weight loss.
Energy expenditure is high in cancer patients while glucose
intolerance is found frequently and may be due to the increased insulin
resistance or inadequate insulin release. Abnormalities also occur in fat
metabolism and include excess body fat depletion, protein loss, increased
lipolysis, changes in free fatty acid and glycerol turnover, as well as
decreased lipogenesis.
Abnormalities in protein metabolism include increased whole
body protein turnover, increased hepatic protein synthesis, persistent muscle
protein breakdown, and decreased levels of plasma branchedchain amino acids.
Malabsorption as well as protein loss through the gastrointestinal tract may
also occur.
DIET AND CANCER RISK
Diet may have either positive and negative influences on
cancer risk. About 35% of cancer occurrence is related to dietary factors. The
role of diet in cancer etiology is summarized in Table 8. Dietary fat intake
was associated with breast cancer in animals as early as 1942. More recently,
higher intake levels of dietary fat have been related to increased risk of colon
cancer. Positive correlations between per capita fat intakes and breast cancer
rates have been described. It has been argued, however, that it may be the high
food energy intake that is causative rather than the percentage of the food energy
coming from dietary fat.
Nevertheless, diets high in fat, particularly saturated fat,
have also been associated with a higher incidence of cancer of the colon,
prostate, and breast. Increased consumption of fruits and vegetables has been
recommended to reduce cancer risk as these foods contain protective factors.
Many are also high in fiber, an increased consumption of
which has been associated with decreased risk of cancer (especially colon
cancer). Diets high in plant foods, starches, fiber, and various carotenes are
commonly associated with a lower incidence of alimentary tract cancers. A
number of dietary and nondietary factors have been found to decrease the
incidence of various cancers. Lycopene found in tomatoes appears to be
protective against colorectal cancer as it can scavenge peroxyl radicals and
quench singlet oxygen.
Increased intakes of plants of the cabbage family appear to
be protective against certain cancers. More recently, broccoli sprouts have
been shown to contain high levels of the anticarcinogenic chemical
sulforaphane. This compound has been known to help mobilize the body's natural
cancerfighting resources and reduces the risk of developing cancer.
ANOREXIA NERVOSA AND BULIMIA NERVOSA
Although not included within the category of nutritionally
related chronic diseases, the eating disorders anorexia nervosa and bulimia
nervosa are important. These diseases are primarily disorders of perception of
body image and are characterized by an excessive concern over being fat.
They are often regarded as modern disorders despite the fact
that similar conditions have been recognized in medicine for more than a
century. Anorexia nervosa is a condition of self-engendered weight loss whose
occurrence was originally thought to be restricted to young women. It also
occurs in young men who are concerned with their body image such as dancers and
models.
The diseases appear to be largely confined to affluent
societies that espouse Western cultural ideals. Diagnostic criteria include:
refusal to maintain minimally normal body weight for age and height; intense
fear of gaining weight or becoming fat, even though already underweight; undue
influence of body weight or shape on selfevaluation; and denial of the
seriousness of the current low body weight with amennorhea often occurring in
postmenarchal females.
Associated symptoms include: depressed mood, irritability,
social withdrawal, loss of sexual libido, preoccupation with food and rituals,
as well as reduced alertness and concentration. One form of the disease invokes
restrictive feeding behavior commonly associated with normal dieting, such as
undereating, refusal to take high-energy foods, and strenuous exercise.
This behavior is abnormal only in the degree to which it is
pursued. Restlessness is very common once emaciation sets in and continues
until physical deterioration leads to weakness and lassitude. The
"purging" form involves more dangerous behaviors, such as
self-induced vomiting, and laxative or diuretic use. Bulimia nervosa is a
variant of anorexia nervosa and shares many of its clinical and demographic
features. It is closely related to the purging form of anorexia nervosa.
One of the major differences is that bulimic patients
maintain normal weight. The condition generally involves persistent dietary
restriction that is eventually interrupted by episodes of binge eating with
compensatory behaviors such as vomiting and laxative abuse. Behavioral
disturbances often become the focus of intense guilt feelings. In the early
stages of the disease, all patients attempt to control their weight by dieting
and abstaining from high-energy foods.
Table 8. Dietary Factors and Cancer Etiology
|
Carcinogenic dietary factors |
Anticarcinogenic factors |
|
Energy excess associated with increased cancer mortality
in men and women |
Energy deficit inhibits tumor growth |
|
Amount and type of fat in the diet also related to
increased cancer risk; high saturated fat, cholesterol, and low
polyunsaturated fat are risk factors |
High levels of monounsaturated fat in the diet show decreased incidence
of certain cancers |
|
High protein intake associated with increased risk of
enhanced tumorigenesis |
High levels of fiber from fruits and vegetables are
associated with low levels of colon and rectal cancer. |
|
Zinc deficiency associated with increased risk of tumors |
Vitamin A and its analogues and precursor (carotenids) are possible
inhibitors of carcinogenesis; ^-carotene may be protective in a mechanism
independent of its role as a vitamin A precursor |
|
Excess alcohol intake High intake of coffee is a possible
risk factor |
Vitamin C has antioxidant properties that may influence
tumorigenesis |
|
Artificial sweeteners such as saccharin increase risk of
bladder cancer |
Vitamin E as an intracellular antioxidant may protect against
carcinogens |
|
Nitrates, nitrites, and nitrosamines may be causative
factors of gastric cancer |
Calcium intake has a inverse association with colon
cancer risk |
|
Methods of food preparation, such as charcoal broiling,
smoking food, and frying, may increase risk |
Selenium intake has been associated with decreased tumor growth in
animal models |
They are constantly preoccupied by thoughts of food, but their pattern of eating alternates between fasting and gorging. Patients are extremely secretive about their bulimic episodes. It is this secrecy that makes the condition difficult to diagnose. Both conditions occur predominantly in industrialized, developed countries and are rare elsewhere.
Immigrants are more likely to develop eating disorders than
their peers in their country of origin, probably indicating the importance of
sociocultural factors in the etiology and distribution of these disorders.
CONCLUSION
The chronic, nutritionally related diseases just described
are major causes of death and disability in rich industrialized countries.
American and North European diets have tended to be high in animal foods (meat,
dairy, fish, eggs) and low in foods of plant origin (grains, fruits, and
vegetables). It is claimed by Garrow that most of the chronic diseases in the
Western society are the manifestation of the high availability and variety of
foods leading to overconsumption.
Only a small
proportion of income is now required to be spent on food in the industrialized
countries. Excessive intake of animal foods leads to a dietary pattern that is
high in saturated fat and cholesterol and low in fiber. In contrast, the
southern European or the Mediterranean diet comprises fruits, vegetables, and
grains with smaller amounts of meat, fish, eggs, and dairy products.
Olive oil is often the major lipid, so that the diet is low
in cholesterol and saturated fat and high in monounsaturated fatty acids. A
comparative study between Italians and Americans was performed in the early
1950s. It was found that Italian diets were remarkably low in fat (20% of
energy) or just half of the proportion observed in the diets of comparable
American groups. The typical American diet, rich in meat and dairy fats was
thus, together with higher concentrations of blood cholesterol, identified with
increased risk of coronary heart disease. A seven-country study performed over
20 years confirmed these relationships.
Recommendations for the "Mediterranean Diet" have
become popular within the United States. This diet plan is indicated in Table 9.
Ironically, while such diets are now being consumed by the affluent, recent
dietary surveys carried out on the island of Crete have reported an increase in
intake of meat, fish, and cheese and a decrease in intakes of bread, fruit,
potatoes, and olive oil.
Similar changes have been observed in Italy. An increased
availability of animal foods throughout the Mediterranean area has also been
documented. These dietary changes have been accompanied by increases in chronic
disease risk factors such as higher concentrations of serum cholesterol,
hypertension, and obesity as well as reduced levels of physical activity.
Chronic disease risk is increasing, not only in the Western society, but also
in the more affluent classes of the developing countries.
The rich in poor countries often have a similar pattern of
food consumption to that observed in the affluent countries. They are also
subject to many of the same lifestyle factors, including smoking and reduced
physical activity. Dietary Guidelines (Table 3) can help in reducing both heart
disease and cancer risk. The guidelines now emphasize moderation in intake,
especially of saturated fat, along with increased physical activity. Increasing
intakes of fruits, vegetables, and complex carbohydrates are also recommended.
Paradoxically, these present recommendations for the affluent
define diets and lifestyles closer to those common in the past for the less
affluent. As a further paradox, these latter societies, as their wealth
increases, are often attempting to emulate the diets and lifestyles of the
West. Consequently, they are now increasingly subject to the same pattern of
disease.
Table 9. The Mediterranean Diet Plan
|
Frequency of consumption |
Foods |
|
Daily |
In significant amounts |
|
Whole grains and grain products (breads, pasta, rice, couscous, polenta,
bulgur) and potatoes |
|
|
Fruits and vegetables |
|
|
Beans, other legumes, and nuts |
|
|
In small or minimal amounts |
|
|
Daily |
Cheese and yogurt |
|
A few times a week |
Fish, poultry, eggs, and sweets |
|
A few times a month |
Red meat (or in small amounts more often) |
|
In addition, regular physical activity is important.
Moderate wine consumption is optional. |
|
