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Obesity

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Title: Obesity


1
Obesity
  • Dr. Sumbul Fatma

2
Overview
  • Definition
  • Prevalence
  • Consequences of Obesity
  • Assessment of Obesity
  • Causes of obesity

3
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

4
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.

5
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)

6
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.

7
Calculating BMI
  • Calculate Body Mass Index (BMI)
  • weight (kg)
  • height squared (meters)
  • Or
  • weight (pounds) x 703
  • height squared (inches)

8
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
9
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10
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.

11
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

12
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

13
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

14
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15
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

16
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

17
  • 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

18
  • 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.

19
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20
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

21
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

22
  • 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.

23
  • 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

24
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

25
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

26
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?

27
Reference
  • Lippincotts Illustrated Reviews of Biochemistry
    4th Edition

28
Thank You!
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