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The percentage of overweight children in the United States has
more than tripled since 1980 with the greatest impact occurring
among minority and economically disadvantaged children.1 Globally,
it is currently estimated that 1 in 10 school-aged children is overweight
(roughly 155 million children) and 30 to 45 million of those children
are considered obese.2 For children under the age
of 5 years, a further 22 million children are considered overweight.3 These
findings suggest a very troubling future given that the likelihood
of obesity persisting into adulthood increases from 20% at
4 years of age to 80% by adolescence and that obesity increases
the risk for a myriad of weight-related health complications.4
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To better understand the pathobiology of obesity, it is useful
to review the process by which adipose tissue is created. From an
evolutionary prospective, it is beneficial to store energy during
periods of energy availability in preparation for very likely periods
of food scarcity. The body stores the available excess energy in
the form of triglycerides within fat cells that reside within the
adipose tissue. This tissue is widely distributed throughout the
body and can store a tremendous amount of excess energy. When food
scarcity limits energy intake, the body then releases the stored
energy in the form of free fatty acids, providing a survival advantage.
A delicate balance exists, and even small, subtle changes in lifestyle
can begin leading a person toward obesity. A small but regular increase
in calories or cessation of a regular physical activity can tip
the balance toward overweight and obesity. In our current Western
environment, food scarcity is uncommon with readily available high-density
caloric foods being relatively inexpensive.
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The factors that influence an individual’s intake-to-expenditure
ratio are nearly limitless. Children are confronted on a daily basis with
a tremendous amount of marketing encouraging the consumption of
high-calorie, high-fat, and high-sugar foods and drinks. They become
progressively more sedentary as they are encouraged to engage in
activities like video games, the Internet, and television. More
subtle influences may include neighborhoods that are too dangerous
for children to play outside, inadequate sleep, parents who do not
model appropriate health behaviors, and governmental policies. These
influences alter the child’s intake-to-expenditure energy
ratio.
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An individual’s genetics also plays a significant role
in the development of weight and weight-related problems. Children
who are adopted possess body mass indices that are more closely
related to their biological than to their adoptive parents.5 Apart
from genetic risk, an individual’s obesity risk is also
shaped by the environment and biological factors, such as leptin,
ghrelin, adiponectin, and other hormones that affect specific metabolic
functioning, such as appetite, satiety, and fat distribution.6
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Internationally, as cultures begin experiencing economic growth,
technological advances, and increased modernization, including entering
the global food market. Diet generally changes such that simple
diets high in complex carbohydrates shift toward a more varied diet
that contains higher amounts ...