Outline

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

2. 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

3. 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

4. 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

5. 5 Classification and Diagnosis

6. 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)

7. 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

8. 1991 1993 < 10% 10% to 15% > 15% 1995 1998 8 Obesity Trends in US Adults AH, et al. JAMA. 1999

9. 9 Obesity Trends in US Adults…

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

11. 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

12. 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

13. 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

14. 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.

15. 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.

16. 16 Energy Production

17. 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

18. 18 Energy Balance

19. 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

20. 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

21. 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.

22. 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.

23. 23 Energy Balance

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

25. 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

26. 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)

27. 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)

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

29. 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.

30. 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

31. 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.

32. 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

33. 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

34. 34 Influences of Satiety…

35. 35 Influences of Satiety

36. 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

37. 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

38. 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

39. 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

40. Thank you for gracing the session! Any question?