Obesity

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Obesity

• Dr. Sumbul Fatma

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Overview

• Definition
• Prevalence
• Consequences of Obesity
• Assessment of Obesity
• Causes of obesity

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Definition

• Obesity is a disorder of body weight regulatory
  systems characterized by an accumulation of
  excess body fat usually 20 percent or more over
  an individual's ideal body weight.
• A combination of abundance of food with reduced
  activity levels found in industrialized
  societies, has resulted in a tendency for the
  sustained deposition of fat

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Prevalence

• The prevalence of obesity increases with age.
  Particularly alarming is the explosion of
  childhood obesity, which has shown a three fold
  increase in prevalence over the last two decades.
  
• As adiposity has increased so has the risk of
  developing associated diseases, such as diabetes,
  hypertension, and cardiovascular disease.

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Prevalence of Obesity

• Childhood and adolescent obesity increased from
  5 to 16 in the last 20 years
• Adulthood obesity increased from 12 to 21 in 10
  years.
• 16 million US adults with BMI over 35
• 60 million US obese adults (BMI gt 30)

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Assessment

• Body mass index (BMI) is an indirect measure of
  obesity and correlates with the amount of body
  fat in most individuals. (exceptions are athletes
  who have large amounts of lean muscle mass)
• The BMI gives a measure of relative weight,
  adjusted for height. This allows comparisons both
  within and between populations.

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Calculating BMI

• Calculate Body Mass Index (BMI)
• weight (kg)
• height squared (meters)
• Or
• weight (pounds) x 703
• height squared (inches)

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Definition of Overweight Obesity

• Using BMI

BMI GRADE
UNDER WEIGHT 18.5
NORMAL 18.5 24.9
OVER WEIGHT 25.0 29.9
OBESITY 30.0 34.9 I
OBESITY 35.0 39.9 II
EXTREME OBESITY 40 III
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Anatomic differences in fat deposition

• It has a major influence on associated health
  risks.
• Android, apple-shaped, or upper body obesity is
  the excess fat located in the central abdominal
  area of the body
• is associated with a greater risk for
  hypertension, insulin resistance, diabetes,
  dyslipidemia, and coronary heart disease
• waist to hip ratio of more than 0.8 for women and
  more than 1.0 for men.

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Anatomic differences in fat deposition

• Gynoid, pear-shaped, or lower body obesity -
  Fat distributed in the lower extremities around
  the hips or gluteal region.
• waist to hip ratio of less than 0.8 for women
  and less than 1.0 for men.
• The pear shape is relatively benign healthwise,
  and is commonly found in females
• Waist-to-hip ratio is a better predictor of
  myocardial infarction than BMI

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Biochemical differences in regional fat depots

• Abdominal fat cells are much larger and have a
  higher rate of fat turnover than lower body fat
  cells
• Hormonally more responsive than adipocytes in
  the legs and buttocks
• As men tend to accumulate the readily
  mobilizable abdominal fat, they generally lose
  weight more readily than women do
• Substances released from abdominal fat are
  absorbed via the portal vein and, thus, have
  direct access to the liver
• Gluteal fat- free fatty acids from gluteal fat
  enter the general circulation, and have no
  preferential action on hepatic metabolism

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Number of fat cells

• When triacylglycerols are deposited in
  adipocytes, the cells increase in size and when
  the ability of a fat cell to expand is limited,
  and when its maximal size is reached, it divides
• Obesity involves an increase in both the number
  and size of adipocytes
• Fat cells, once gained, are never lost
• An obese individual, with increased numbers of
  adipocytes, will have to reduce the size of those
  fat cells in order to normalize fat stores. These
  individuals will be in the doubly abnormal state
  of having too many, too small fat cells.
• Formerly obese patients have a particularly
  difficult time maintaining their reduced body
  weight

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Body weight regulation

• The body weight of most individuals tends to
  range within ten percent of a set value
• This observation prompted the theory that each
  individual has a biologically predetermined set
  point for body weight

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Set Point Theory

• The body attempts to add adipose tissue when the
  body weight falls below the set point, and to
  lose weight when the body weight is higher than
  the set point
• Weight loss weight gain
• Appetite increases
  Appetite falls
• Energy Exp. Falls Increases

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• Strict set point model does not explain why some
  individuals fail to revert to their starting
  weight after a period of overeating, or
• the current epidemic of obesity

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• Body weight, rather than being irrevocably set,
  seems to drift around a natural settling point,
  which reflects a balance between factors that
  influence food intake and energy expenditure
• Body weight is stable as long as the behavioral
  and environmental factors that influence energy
  balance are constant.

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Factors predispose to obesity

• Genetic familial tendency
• Environmental and behavioral
• Sex women more susceptible
• Activity lack of physical activity
• Psychogenic emotional deprivation, depression
• Social class poorer classes
• Alcohol problem drinking
• Smoking cessation smoking
• Prescribed drugs tricyclic derivatives

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Genetic contributions to obesity

• Despite the widely held belief that obesity is a
  result of uncontrolled, gluttonous eating
  behavior, it is now evident that genetic
  mechanisms play a major role in determining body
  weight
• Obesity is often observed clustered in families.
  If both parents are obese, there is a 7080
  chance of the children being obese. In contrast,
  only 9 of children were fat when both parents
  were lean

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• The inheritance of obesity is not simple
  Mendelian genetics as would be expected if the
  condition were a result of a defect in a single
  gene. Rather, obesity behaves as a complex
  polygenic disease involving interactions between
  multiple genes and the environment
• The importance of genetics as a determinant of
  obesity is also indicated by the observation that
  children who are adopted usually show a body
  weight that correlates with their biologic rather
  than adoptive parents
• Furthermore, identical twins have very similar
  BMI, whether reared together or apart, and their
  BMI are more similar than those of nonidentical,
  dizygotic twins.

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• The epidemic of obesity occurring over the last
  decade cannot be explained by changes in genetic
  factors, which are stable on this short time
  scale
• Environmental factors, such as the ready
  availability of palatable, energy-dense foods,
  play a role in the increased prevalence of
  obesity
• Furthermore, sedentary lifestyles enhance the
  tendency to gain weight
• When Japanese or Chinese populations migrate to
  the United States, their BMI increases. For
  example, men in Japan (aged 4649 years) are
  lean, with an average BMI of 20, whereas Japanese
  men of the same age living in California are
  heavier, with an average BMI of 2
• Eating behaviors, such as snacking, portion size,
  variety of foods consumed, an individual's unique
  food preferences, and the number of people with
  whom one eats also influence food consumption and
  the tendency toward obesity

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Weight Gain How Does It Happen?

• Energy imbalance
• calories consumed not equal to calories used
• Over a long period of time
• Due to a combination of several factors
• Individual behaviors
• Social interactions
• Environmental factors
• Genetics

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Weight Gain Energy In

• 3500 calories 1 pound
• 100 calories extra per day
• 36,500 extra per year
• 10.4 lbs weight gain
• Question How much is 100 calories?
• Answer Not very much!
• 1 glass skim milk, or
• 1 banana, or
• 1 slice cheese, or
• 1 tablespoon butter

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Evolving Pathology

• More in and less out weight gain
• More out and less in weight loss
• Hypothalamus
• control center for hunger and satiety
• Endocrine disorder
• where are the hormones?

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Reference

• Lippincotts Illustrated Reviews of Biochemistry
  4th Edition

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Thank You!