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Welcome to Session on Obesity Meera Kaur, PhD, RD Assistant Professor Department of Family Medicine Faculty of Medicine

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Presentation on theme: "Welcome to Session on Obesity Meera Kaur, PhD, RD Assistant Professor Department of Family Medicine Faculty of Medicine"— Presentation transcript:

1 Welcome to Session on Obesity Meera Kaur, PhD, RD Assistant Professor Department of Family Medicine Faculty of Medicine

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 2

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 3

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 4

5 Classification and Diagnosis 5 ClassificationBMI (kg/m2)Risk of Co-morbidities Underweight<18.5 increased risk in other areas Desirable Average Overweight Mildly Increased Obese>30.0 Class I Obesity Moderate Class II Obesity Class III Obesity >40.0 Severe Very severe

6 Classification for Children (<2 Years) BMI Status Normal weight for height10 th -90 th percentile At risk for overweight85 th -95 th percentile Overweight>95 percentile (Centre for Disease Control and Prevention, 2005) 6

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 >

8 Obesity Trends in US Adults < 10% 10% to 15% > 15% AH, et al. JAMA. 1999

9 Obesity Trends in US Adults… 9

10 10 Obesity Trends in US Adults, 2004 No Data <10% 10%–14% 15%–19% 20%–24% ≥25%

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 11

12 Juvenile-Onset Obesity Develops in infancy or childhood Increase in the number 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 12

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 13

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. 14

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. 15

16 Energy Production 16

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 17

18 Energy Balance 18

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 19

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 20

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. 21

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  when energy 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. 22

23 Energy Balance 23

24 Ultimate Energy Balance 24 TEF REE NEAT Physical activity Dietary Intake

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 25

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) 26

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) 27

28 Regulatory Factors in Feeding and Adiposity Brain Neurotransmitters Gut hormones Other hormones 28

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. 29

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 30

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. Peotide YY-3-36 (PYY ) is secreted in small bowel in response to foods. –In obesity it loses the ability to inhibit energy intake. 31

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 32

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 33

34 Influences of Satiety… 34

35 Influences of Satiety 35

36 What it Takes to Lose a Pound 36 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 kcal to lose a pound per week

37 Do the Math To lose one pound, you must create a deficit of 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 kcal per day kcal x 7 days = kcal = 1 pound of weight loss day weekin 1 week 37

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 38

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 39

40 Thank you for gracing the session! Any question?


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