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The developed nations of the world are presently
facing an obesity epidemic of staggering proportions. The adverse health
consequences of overnutrition and malnutrition represent a matter of serious
concern not only to those populations directly affected, but also to those
living in developing countries to which these problems are being insidiously
exported.
That nutrition plays an essential role in the maintenance of human
health and well-being is well understood. There is ample scientific evidence
to suggest that diet and nutritional status have a tremendous impact on
an individual’s relative risk of developing numerous non-communicable
diseases, including hypertension, heart disease, non-insulin dependent
diabetes, breast and colon cancer, obesity and osteoporosis. The World
Health Organization (WHO) has asserted that the underlying determinants
of these non-communicable diseases are largely the same world-wide, and
include (1) increased consumption of energy-dense, nutrient-poor foods
that are high in fat, sugar and salt, and (2) reduced levels of physical
activity.
In addition to the effect of diet on individual wellness, population
health parameters are significantly influenced by cultural dietary practices.
National and regional traditions and customs, along with religious tenets
and political motives and initiatives all impact how, what, why and even
when we eat - both individually and collectively. Studies have demonstrated
that the interaction of cultural dietary habits with a population’s
genetic predisposition strongly influences population health. However,
with the inexorable dissemination of economic entities and cultural practices
from industrialized nations to the developing world (a process that has
come to be known as “globalization”), such epidemiologic diversity
of diet and disease is becoming increasingly rare. The eating patterns
of developed nations are progressively being adopted throughout the developing
world, with predictably adverse public health consequences. Of particular
concern are the increasingly unhealthy diets and reduced physical activity
patterns of children and adolescents. Indeed, the WHO 2002 World Health
Report observed that the burden of morbidity and disability attributable
to non-communicable diseases now weighs heaviest in the developing countries,
where those affected are (on average) younger than in the developed world.
Many nations throughout the world are now confronted with rapidly escalating
rates of obesity. Nowhere is the problem more dire than in the USA, where
more than 60% of adults and 25% of children are either obese (Body Mass
Index [BMI] = 30) or overweight. In 1991, only four of America's 50 states
claimed a prevalence of obesity in excess of 15%. Today, at least 37 states
have rates exceeding 15%. Between 1960 and 2000, the prevalence of obesity
among adults aged 20 to 74 years in the United States increased from 13.4%
to 30.9%. An estimated 325000 deaths and 4.3% to 5.7% of direct health
care costs (approximately US $39 to $59 billion annually) are attributed
to obesity. Childhood obesity has reached epidemic proportions. Some 4.7
million youth 6 to 17 years of age are overweight or obese. The number
of overweight youth has more than doubled over the past thirty years.
From a public health perspective, obesity ranks second only to smoking
as a cause of non-communicable diseases and associated mortality in the
US.
The dramatic surge in obesity has paralleled the global increase in
consumption of foods from "fast food" franchises. These foods
are not only "engineered" to be higher in fat and refined carbohydrates
than the less processed and refined "traditional" foods that
they ultimately replace, but are also typically served in "super-sized"
portions that dramatically exceed the caloric needs of the average individual.
Although the McDonald’s restaurant chain has frequently been targeted
by the opponents of economic globalization as emblematic of the problems
that have accompanied the phenomenon, McDonald’s is only one of
many fast food restaurants clamoring for our business through omni-present
advertising. Born in post-World War II America, the “fast food”
industry now carries almost unimaginable economic clout - to say nothing
of its effect on the health of the industrialized world. In his book “Fast
Food Nation”, Eric Schlosser chronicles the history of the fast
food segment of the American economy. Schlosser reports that whereas in
1970 Americans spent roughly $6 billion on “fast food”, in
2000 they spent in excess of 110 billion dollars - more than was spent
on movies, books, magazines, newspapers, videos and recorded music combined.
In this new millennium, nearly 25% of the adult population in the United
States consumes fast food on any given day. Globalization has permitted
the metastasis of the fast food culture, with its attendant health sequelae.
As a case in point, between1984 and 1993 the number of fast food restaurants
in Great Britain doubled - as did the prevalence of obesity among adults.
The growing “fast food” culture of industrialized societies
is symptomatic of a broader, evolving cultural phenomenon that discourages
individual responsibility and control over the quantity and quality of
foods consumed. Some of the trends that contribute to this problem include:
It is a common misconception that affluence is a precondition for obesity.
Rather, malnutrition and obesity often afflict low-income households through
a phenomenon known as “food insecurity”, in which relatively
inexpensive foods that are filling but also high in fat, sugar, and calories
are purchased in an effort to maintain a sense of satiety. Unfortunately,
these foods are nutritionally depleted, and offer the unsuspecting consumer
a false sense of nutritional security. According to a recent WHO report,
the impact of a diet high in energy-dense refined foods on world population
health is being most significantly felt in developing countries, where
it may be contributing to both the economic and social stratification
of those societies.
Perhaps the segment of the population most dramatically affected by
the observed shift in the global dietary paradigm is the world’s
youth. The incidence of glycemic dyscontrol among the youth of the industrialized
world is skyrocketing. The increased incidence of diabetes mellitus among
this demographic is without doubt also related to the burgeoning obesity
crisis. The long-term health implications and societal cost of this epidemic
of obesity and nutritional decline therefore will probably not be understood
or fully appreciated for years to come. However, one probable consequence
of the global shift in dietary patterns that is already apparent is the
so-called “metabolic syndrome”. Characterized by obesity and
systemic inflammation, the metabolic syndrome is also defined by elevated
triglycerides, reduced high density lipoprotein, elevated blood pressure,
and fasting hyperglycemia. Studies have reported an age-adjusted prevalence
of 23.7% among adults living in the United States, while 4% of US adolescents
are thought to have this condition. The prevalence of the metabolic syndrome
increases to nearly 29% among adolescents who are significantly overweight
(defined as youth aged 12 - 19 with a BMI=95%ile).
Where should we look for solutions to this burgeoning and worrisome
public health problem? The "cure" for obesity appears as elusive
as ever. Energy balance may be defined as the difference between the number
of calories consumed and the number of calories expended. If an individual
maintains a negative energy balance, over time they will lose weight.
Conversely, an individual in positive energy balance (in which caloric
intake consistently exceeds caloric expenditure) will gain weight. As
human beings, our body chemistry is programmed to store excess calories
in “banks” of adipose tissue, from where it may be mobilized
in times of need. Increasingly, the need to draw upon these important
energy reserves is becoming more and more rare, since food is not only
more abundant but we expend less energy by virtue of increasingly sedentary
lifestyles. As caloric intake has risen, caloric expenditure from activity
and exercise has steadily declined. Close to 60% of Americans exercise
rarely or not at all. Children who watch more than 5 hours of television
a day are five times as likely to be overweight than children who watch
less than 2 hours a day. Only 25% of young Americans ages 12-21 years
participate in light to moderate activity daily. Industrialization, modernization,
and urbanization are all suspected of contributing to this insidious and
progressive lack of physical activity which contributes as much to the
high prevalence of overweight and obesity as unhealthy eating behavior.
The United States Federal Government, along with many other organizations
including the American College of Sports Medicine, has published recommended
“aerobic exercise guidelines” designed to help educate the
general public regarding the need for and the benefits of regular exercise.
In general, exercise should be performed no less than three to five times
per week. Endurance exercise performed within the aerobic range is felt
to be most effective at “burning” fat, but all activity should
be considered to be beneficial and therefore encouraged. Walking, climbing
stairs, and other activities of daily living have cumulative effects on
caloric expenditure that over time may significantly shift an individual’s
energy balance towards weight loss. The ACSM recommends that “if
weight loss is the major goal, participate in your aerobic activity at
least 30 minutes for five days each week”(Fig 1).
Figure 1 ![]() Recognizing the importance of exercise in the weight loss equation
does not mean, however, that we should ignore the role of diet in maintaining
energy balance. The amount of caloric energy required by humans varies
based on a number of factors including genetics, gender, health status,
metabolic demands, climate, body weight, and stress. Estimates of the
minimum daily caloric requirement vary, but it is generally agreed that
the average person in the richest countries consumes 30-40% more calories
than is needed, while people in poorer countries typically consume 10%
fewer calories than is considered optimal. In addition to balancing one’s
individual energy equation, macronutrient consumption should fall within
recommended guidelines. The Institute of Medicine’s Acceptable Macronutrient
Distribution Range (AMDR) for adults is expressed in terms of percentage
of total energy intake: 45 to 65% carbohydrates, 20 to 35% fat; and 10
to 35% protein. The AMDR for children ages 4 to 18 years is 45-65% carbohydrate,
25-35% fat and10-30% protein. Obviously, tremendous dietary diversity
is possible within these stated ranges, and further research is needed
to link specific intakes to optimum health outcomes.
With so many dietary choices to make, it is natural to ask “what
diet is best?” The answer to this question requires a reductionist
view that may not be entirely appropriate on a population basis. Indeed,
a single “best” diet may be unreasonable to prescribe since
there are undoubtedly genetic differences between (and even within) various
populations and cultures. For instance, Native Americans have been found
to have a high prevalence of the so-called “thrifty gene”
that predisposes individuals to deposition of body fat stores, and may
trigger an obese phenotype if the individual is exposed to a diet high
in refined foods. Furthermore, a diet that promotes weight loss may not
be the best diet for long-term health maintenance. Nevertheless, it seems
reasonable to conclude that the “proper” diet should at a
minimum take into account existing or known health conditions (diabetes,
cardiovascular disease, dyslipidemia, chronic illness) and the baseline
energy expenditure of the individual. For example, athletes require more
calories per day than do non-athletes in order to maintain proper energy
balance. The sport in which one participates should also influence dietary
choices, since diet can affect the availability of energy stores during
training and competition.
While a review of the biochemistry and physiology of energy substrate
utilization is beyond the scope of this article, it is instructive to
recall that while the human body is capable of utilizing a variety of
substrates for energy production, the preferred sources of energy are
carbohydrates and fats. This is reflected in our body’s intrinsic
energy storage mechanisms. Carbohydrate in the form of glucose (or stored
as glycogen) is the body’s preferred and most readily accessible
source of energy. However, an average individual has sufficient stores
for only 90-100 minutes of exercise. Fats, on the other hand, are not
only a more energy-rich storage medium (releasing 37 kJ per gram compared
to 16 kJ per gram for carbohydrate) but may also be found in significantly
greater abundance than carbohydrate stores: the average human has sufficient
fat stores to (in theory) support up to 80 hours of exercise. Note that
protein, while in abundant supply, is an inefficient source of energy
and is the body’s least preferred energy source. These observations
form the basis for the popular low carbohydrate diets (eg the Atkins Diet
and the South Beach Diet). A great debate is currently waging about the
relative merits of these high protein, high fat, low carbohydrate diets.
Advocates claim that diets high in protein and lower in carbohydrate promote
metabolism of adipose tissue in the relative absence of preferred energy-rich
carbohydrate and result in rapid weight loss without significant adverse
effects. Long term studies have not been conducted to confirm this claim,
however, and numerous professional organizations such as the American
Dietetic Association and the American Heart Association have cautioned
against such diets out of concern over possible adverse affects on serum
lipids, insulin and liver and kidney function.
If, as suggested, the “fast food culture” plays a considerable
role in the world-wide obesity epidemic, it seems appropriate to ask whether
modifying our food culture might reverse the process. While the answer
to this question may be ultimately unknowable, such thinking forms the
foundation of a relatively recent world-wide cultural movement known as
“Slow Food”. The Slow Food movement seeks to restore the “kitchen
and the table as centers of pleasure, culture, and community” by
promoting sustainable stewardship of the land and ecologically sound food
production, renewal of culinary traditions, and a return to a “slower
and more harmonious rhythm of life”. In essence, Slow Food is the
antithesis of fast food and dietary globalization. The Slow Food movement
was born in Italy in 1986; the international organization was established
in Paris in 1989. The movement encourages members (who number approximately
75000 world-wide) to support local growers and like-minded businesses
rather than rely on industrial growers or large scale distributors/retailers.
Although a relatively small organization in the United States, with only
12,500 members, the movement appears to be having an impact: many fast
food chains are adding “healthy” menu choices in an effort
to retain the business of these typically affluent and influential clients.
Despite the apparent promise of the Slow Food movement, it is nevertheless
evident that dieting alone is rarely sufficient to lose weight: 95% of
Americans who attempt to lose weight solely by restricting calories fail.
Not surprisingly, as a result of the predictable failure of diet alone
to result in significant weight loss, there has been an increased interest
in surgical beautification and weight loss procedures, ranging from gastric
bypass (bariatric) surgery to liposuction. At the end of the day, however,
there is no substitute for increasing the number of calories expended.
The most convenient and effective means of “burning” calories
is exercise, as discussed above. Not only does aerobic exercise shift
the energy balance toward weight loss, but it bestows other physiologic
and psychological benefits that are conducive to health, including lower
blood pressure, improved glycemic control, and improved self-image.
The trend towards global obesity is a broad spectrum, multifactorial
problem. Solutions will undoubtedly require a transdisciplinary approach.
Nutritionists, dietitians, public health workers and governmental officials,
health care professionals, teachers, parents, city planners and international
organizations such as ICSSPE must work collaboratively to devise integrated
community-based programs that promote and encourage activity, exercise,
and responsible nutrition. If we are to reverse the existing trends, future
behavioral interventions should target the youth. Existing research into
the barriers that prevent children and adolescents from eating healthfully
and exercising regularly suggests that such efforts must address the social
and environmental influences on dietary practices and exercise, including
(but not limited to) parents, teachers, schools and care-givers. Educational
offerings should include instruction in nutrition, time-management, self-motivation,
and sound decision-making skills. School curricula and community programs
should promote and, indeed, reward physical activity and exercise. Over
time such programmatic initiatives may help foster positive, healthy lifestyles.
Equally importantly, such programs may eventually bring economic pressure
for reform to bear on the institutions that have contributed to the demise
of cultural dietary diversity through the process of globalization. Although
the challenge ahead is clearly enormous, to do less invites certain failure.
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Jonathan C. Reeser, MD, PhD,
Marshfield Clinic 1000 North Oak Avenue 54449 Marshfield, WI USA jreeser@charter.net ![]() http://www.icsspe.org/portal/bulletin-january2004.htm |