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Welcome to Session on Obesity Meera Kaur, PhD, RD Assistant Professor Department of Family Medicine Faculty of Medicine kaur@cc.umanitoba.ca http://home.cc.umanitoba.ca/~kaur. 2. Outline. Learning objectives Introduction Classification and diagnosis Obesity trend

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Welcome to Session on Obesity Meera Kaur, PhD, RDAssistant ProfessorDepartment of Family MedicineFaculty of Medicinekaur@cc.umanitoba.cahttp://home.cc.umanitoba.ca/~kaur

outline

2

Outline
  • Learning objectives
  • Introduction
  • Classification and diagnosis
  • Obesity trend
  • Adipose tissue, adiposity, hypertrophy and hyperplasia
  • Energy balance
  • Regulation of body weight
  • Regulation of food intake and body weight
  • Regulatory factors in feeding and adiposity
  • Sound weight loss program
  • Conclusions
  • Questions and answers
learning objectives

3

Learning Objectives
  • To understand
    • the physiological and metabolic perspectives of obesity/overweight, and
    • the regulation of body weight with special reference to:
      • Regulatory factors involved in feeding and adiposity
introduction

4

Introduction
  • Obesity is the disorder of body composition defined by a relative or absolute excess of body fat.
  • The WHO and NHLBI have classified obesity as an epidemic
  • In 2002, ~64% Americans overweight; 32% obese
  • 16% or 9 million kids were overweight
  • Thus, a trend towards an ever-fatter America
  • By 2009, 70% of American expected to be overweight or obese
  • Obesity contributes to +300,000 deaths a year
  • From a global perspective, the increase in the prevalence of obesity is alarming
classification for children 2 years

6

Classification for Children (<2 Years)

BMI Status

Normal weight for height 10th-90th percentile

At risk for overweight 85th-95th percentile

Overweight >95 percentile

(Centre for Disease Control and Prevention, 2005)

assessing obesity

7

Assessing Obesity
  • Waist circumference at level of iliac crest
    • Above 40 inches for men and 35 inches for women are indicative of health risk.
  • Waist-to-hip ratio: Circumference of the waist at the level of L3 divided by the circumference of the hip at the largest area of the gluteal region. (Helps identify central or android obesity.)
    • For men waist-to-hip ratio > 1
    • For women waist-to-hip ratio > 0.85
obesity trends in us adults

1991

1993

< 10%

10% to 15%

> 15%

1995

1998

8

Obesity Trends in US Adults

AH, et al. JAMA. 1999

obesity trends in us adults 2004

10

Obesity Trends in US Adults, 2004

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%

adipose tissue adipocytes hypertrophy and hyperplasia

11

Adipose Tissue, Adipocytes, Hypertrophy and Hyperplasia
  • Adipose tissue
    • White: energy, cushion, insulation
    • Brown: Key regulator of energy expenditure
  • Adipocytes
    • store 80-90% fat as tryglyceride
  • Hypertrophy
    •  adipose tissue due to enlarged adipocytes
  • Hyperplasia
    •  adipose tissue due to  number of adipocytes
juvenile onset obesity

12

Juvenile-Onset Obesity
  • Develops in infancy or childhood
  • Increase in thenumber of adipose cells
  • Adipose cells have long life span and need to store fat
  • Makes it difficult to lose the fat (weight loss)
  • Causes
    • poor dietary patterns
    • lack of physical activity
  • 43% of adolescents watch 2 hours or more of TV/day
adult onset obesity

13

Adult-Onset Obesity
  • Develops in adulthood
  • Fewer (number of) adipose cells
  • These adipose cells are larger (stores excess amount of fat)
  • If weight gain continues, the number of adipose cells can increase
regulation of body weight

14

Regulation of Body Weight
  • Short-term regulation is governed by:
    • Hunger (postabsorptive), appetite and satiety (postprandial)
    • physical trigger for hunger > satiety
  • Long-term regulation is governed by:
    • feedback mechanism– adipocytokines (signaling protein is released from the adipose mass when normal body composition is disturbed. This mechanism plays a greater role in younger persons than older adults.
set point theory

15

Set-Point Theory
  • Fat storage in nonobase adult is regulated to preserve the specific weight.
    • deliberate effort to starve or overfeed are followed by a rapid return to original body weight (set-point).
    • if set-point theory is true, some form of obesity could be due to the abnormally established set-point.
  • Can we establish a new settling-point vs. Set-point to treat obesity?
    • However, data are not conclusive in this area. We need to do more research.
energy balance

17

Energy Balance…
  • State in which energy intake, in the form of food and /or alcohol, matches the energy expended, primarily through basal metabolism and physical activity
  • Positive energy balance

Energy intake > energy expended

Results in weight gain

  • Negative energy balance

Energy intake < energy

Results in weight loss

regulation of energy intake and body weight

19

Regulation of Energy Intake and Body Weight
  • Factors that regulate energy intake and body weights are:
    • Dietary thermogenesis and the Thermic Effect of Foods (TEF)/Specific Dynamic Action (SDA) of foods
    • Resting/Basal Metabolic Rate (RMR)/(BMR)
    • Energy expended in voluntary activity
    • Regulatory neurotransmitters and hormones
thermic effect of foods

20

Thermic Effect of Foods
  • Energy used to digest, absorb, and metabolize food nutrients
  • “Sales tax” of total energy consumed
  • ~5-10% above the total energy consumed
  • TEF is higher for CHO and protein than fat
  • Less energy is used to transfer dietary fat into adipose stores
    • Meal size, meal composition, previous meal, insulin resistance, physical activity and aging influence the TEF.
    • Aerobic exercise the TEF
resting metabolic rate rmr

21

Resting Metabolic Rate (RMR)
  • RMR explains 60-70% of Total Energy expenditure (TEE). When body is deprived of energy
    • RMR adapts to conserve energy by dropping rapidly (up to 15% in two weeks).
  • RMR declines with age
  • During undernutrition, abnormalities in lipolysis may cause insulin resistance affecting RMR
  • The regulation of free fatty acid availability is an important area of research related to the RMR.
activity thermogenesis at

22

Activity Thermogenesis (AT)
  • Energy expended in voluntary activity – activity thermogenesis (AT) is the most important component of TEE (15-30% normally). Therefore, AT should be  whenenergy is not restricted.
  • RMR and Fat free mass (FFM) decrease with age. Hence adjustment between energy intake and AT should be adjusted for preserving normal weight.
  • All activity counts including nonexcercise activity thermogenesis (NEAT).
  • To reverse obesity standing and ambulatory time should be promoted at least 2.5 hours/day.
ultimate energy balance

24

Ultimate Energy Balance

TEF

REE

NEAT

Physical activity

Dietary

Intake

macronutrients and fat storage

25

Macronutrients and Fat Storage
  • Body prefers to use CHO as energy source
  • Only excess intake of CHO and protein will be turned into fat
  • Fat will remain as fat for storage
  • Physical activity encourages the burning of dietary fat (Beta-oxidation)
  • High CHO diet decreases Beta-oxidation
  • Most endurance athletes burn fatty acids for energy
fat storage

26

Fat Storage
  • Fat
    • Most fat is stored directly into adipose tissue
    • Body has ability to store fat (as fat)
  • Carbohydrates
    • Limited CHO can be stored as glycogen Most CHO is used as a energy source
    • Excessive CHO will be synthesized into fat (for storage)
protein and fat storage

27

Protein and Fat Storage
  • Protein is primarily used for tissue synthesis
  • Adults generally consume more protein than needed for tissue synthesis
  • Excess protein is used as a energy source
  • Some protein will be synthesized into fat (for storage)
regulatory factors in feeding and adiposity

28

Regulatory Factors in Feeding and Adiposity
  • Brain Neurotransmitters
  • Gut hormones
  • Other hormones
brain neurotransmitters

29

Brain Neurotransmitters
  • Norepinephrine and Dopamine
    • Released by symphathetic nervous system (SNS)
    • Fasting & starvation  SNS activity, epinephrine that govern feeding behaviour and subatrate mobilization
    • Dopaminnergic pathway in the brain play a role in reinforcement properties of foodds.
  • Serotonin
    •  In serotonin leads to carbohydrate appetite.
  • Corticotrophin-releasing Factor (CRF)
    • CRF is a potent anorexic agent and weakens the feeding response produced by norepinephrine and neuropeptide Y.
    • CRF is released during exercise.
gut hormones

30

Gut Hormones…
  • Incretins is a G-I peptide
    •  insulin release after eating , even before blood glucose level is elevated. Serotonin is a G-I peptide
  • Cholecystokinin (CCK)
    • At brain level inhibits food intake. Stimulates pancreatic enzymes
  • Bombesin
    •  Food intake and enhances the release of CCK.
  • Enterostatin
    • Part of pancreatic lipase;  satiety following fat consumption
gut hormones31

31

Gut Hormones
  • Adiponectin - Adipocytokine secreted by adipose tissue
    • Level of this hormone is inversely related to BMI. Plays role in metabolic disorders.
  • Glucagon causes hypoglycemia
  • Glucagon-like-peptide-1 (GLP-1)
    • Released in presence of glucose rich food, delays gastric emptying time and promote satiety.
  • Leptin is an adipocytokine and regulates appetite.
    • In obesity it loses the ability to inhibit energy intake.
  • Resistin - An adipocytokine that antagonizes insulin action
  • Ghrelin – Produced in stomach and stimulate hunger.
  • PeotideYY-3-36 (PYY -3-36 ) is secreted in small bowel in response to foods.
    • In obesity it loses the ability to inhibit energy intake.
other hormones

32

Other Hormones
  • Thyroid hormone – Modulates the tissue responsiveness to the catecholamines secreted by SNS. A  in thyroid hormone lpwers the SNS activity and adaptive thermogenesis.
  • Vispatin - An adipocytokine protein that has an insulin-like-effect. Plasma level  with  adiposity and insulin resistance.
  • Adrenomedullin - A new peptide secreted by adipocytesas a result of inflammatory process
satiety regulator

33

Satiety Regulator
  • The hypothalamus
    • When feeding cells are stimulated, they signal us to eat
    • When satiety cells are stimulated, they signal us to stop eating
  • Sympathetic nervous system
    • When activity increases, it signals us to stop eating
    • When activity decreases, it signals us to eat
what it takes to lose a pound

36

What it Takes to Lose a Pound
  • Body fat contains 3500 kcal per pound
  • Fat storage (body fat plus supporting lean tissues) contains 2700 kcal per pound
  • Must have an energy deficit of 2700-3500 kcal to lose a pound per week
do the math

37

Do the Math

To lose one pound, you must create a deficit of 2700-3500 kcal

So to lose a pound in 1 week (7 days), try cutting back on your kcal intake and increase physical activity so that you create a deficit of 400-500 kcal per day

- 500 kcal x 7 days = - 3500 kcal = 1 pound of weight loss

day week in 1 week

sound weight loss program

38

Sound Weight Loss Program
  • Meets nutritional needs, except for kcal
  • Slow & steady weight loss
  • Adapted to individuals’ habits and tastes
  • Contains enough kcal to minimize hunger and fatigue
  • Contains common foods
  • Fit into any social situation
  • Change eating problems/habits
  • Improves overall health
  • See a physician before starting
summary and conclusion

39

Summary and Conclusion
  • To treat obesity and/or develop an effective weight loss program, understanding of
    • the physiological and metabolic perspectives of obesity/overweight is important
    • the regulation of body weight with special reference to:
      • Regulatory factors involved in feeding and adiposity is crucial
    • Energy balance is the key point
    • Team approach is important in developing a sustainable weight loss program