| |
Weight
Management Home Obesity
1200
Calorie
Diet
1500
Calorie
Diet
What
is a
Food Portion?
Burn
Barometer
Body
Mass Index (BMI)/Protein
Tool
Trigger
Foods
|
|
 Causes
and Metabolic Consequences of Obesity
Obesity is defined
as excess body fat, and results from a gene-environment interaction. The
deposition of fat when there is excess energy intake relative to expenditure
is entirely normal. While man is well-adapted to starvation as the result
of thousands of years of exposure to irregular food supplies, he is poorly
adapted to overnutrition. In fact, man has only had a surplus of food
in the past 100 years. Therefore, it is not surprising that there has
not been an adaptation to overnutrition. The modern high fat diet combined
with physical inactivity has resulted in an epidemic of obesity and overweight
affecting one of every two Americans. There are clearly individual differences
in metabolism and energy efficiency which are in part inherited. Therefore,
while genetics determines the potential for obesity, diet, exercise, and
lifestyle determine whether and to what extent obesity develops.
The metabolic consequences
of obesity are highly dependent on fat distribution. Increased abdominal
fat accumulation is associated with insulin resistance. While this fat
distribution is called android obesity, it can occur both in men and women.
However, lower body, or gynoid, obesity occurs only in women and castrate
men. Abdominal adipocytes release free fatty acids more readily under
the influence of catecholamines, and these fatty acids in the portal circulation
may engender insulin resistance. Women with abdominal obesity have higher
levels of male hormones than women with lower body fat or gynoid obesity.
In fact, visceral obesity is associated with hyperinsulinemia, hypertriglyceridemia,
glucose intolerance, hypertension, and common forms of cancer. In addition,
polycystic ovarian syndrome, characterized by insulin resistance, dysmenorrhea,
hirsutism and obesity, is more common in women with upper body obesity.
Infertility is also more common in overweight women.
The health consequences
of obesity include some of the most common chronic diseases in our society.
Obesity is an independent risk factor for heart disease, the most common
killer disease in our country. Non-insulin dependent diabetes mellitus,
hypertension and stroke, hyperlipidemia, osteoarthritis, and sleep apnea
are all more common in obese individuals. Weight loss of only 20 pounds
can be associated with marked reductions in the risk of these chronic
diseases. Conversely, adult weight gain is associated with increased risk
of breast cancer in postmenopausal women. Psychiatric disorders are no
more common in obese individuals, but the incidence of mild depression
and anxiety is increased in obese compared to non-obese individuals. It
has not been determined how much of the increased risk is secondary to
the negative reaction of our society to obese individuals versus endogenous
differences associated with obesity. .
Obesity is the most
common nutritional disorder in this country and there has been a thirty
percent increase in the incidence of obesity over the past ten years.
The exact cause of this epidemic has not been determined, but more hectic
lifestyles, with reduced time for exercise and increased caloric intake,
have been identified as potential factors. The intake of fat has increased
over the last eighty years, but the increased incidence of obesity was
observed despite the availability of over 1,000 so-called fat-free foods.
When sugar replaces fat in these foods, there is often no difference in
caloric content as compared to the full-fat version, so that consumption
of fat-free foods does not reduce calorie intake.
Obesity is a complex
disorder for which no simple single solution will suffice.
Diagnosis
and Vertically Integrated Management of Obesity
|
|
