Slide 1How do we define obesity?Slide 3Slide 4Slide 5Children and ObesitySlide 7Slide 8Health risks of obesityObesity is associated with risks to healthBMI, health and mortalityBMI and All-Cause MortalityWhat causes obesity?Energy imbalance effectsAssessment of ObesityAssessment of ObesityIs BMI good measure of obesity?Types of fatTypes of fatFat depots and diseaseVisceral Adipose Tissue and diseaseVisceral Adipose Tissue and disease Britton, et al 2013 JACC.Visceral Adipose Tissue and diseasesummaryWhat is obesity and why do we care about it? Fall 2017Obesity Lecture 1How do we define obesity?Excess body fat with multiple organ specific pathological consequences–In other words, excess body fat associated with negative health effectsWith a BMI of: You are considered:Below 18.5 Underweight18.5 - 24.9 Healthy Weight25.0 - 29.9 Overweight30 or higher ObeseObesity class BMI (kg/m2)Class I 30.0- 34.9Class II 35.0-39.9Class III (Extreme Obesity) ≥ 40.0How serious is the issue?2000Obesity Trends* Among U.S. AdultsBRFSS, 1990, 2000, 2010(*BMI 30, or about 30 lbs. overweight for 5’4” person)20101990No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%Children and ObesityThe estimated annual medical cost of obesity in the U.S. was $147 billion in 2008 U.S. dollarsHealth risks of obesity•Type 2 diabetes, heart disease, high blood pressure, stroke, certain types of cancer (colon, rectal, prostate, gall bladder, uterus, cervix, ovaries)•Gall bladder, fatty liver disease acid reflux•Osteoarthritis•Breathing problems•Reproductive problems•Psychological and social problems•44% of the diabetes, 23% of the ischemic heart disease and between 7% and 41% of certain cancer burdens are attributable to overweight and obesity.Obesity is associated with risks to healthNote: US data, 1999.BMI, health and mortality•1.4 – 2.8 greater risk of CVD mortality among high BMI groups (BMI = 27.5 – 29)•Diabetes risk is greater in overweight groups – evidence of dose-response RR: 3.6 with BMI = 26-27.9RR: 5.2 with BMI = 28 -29.9BMI and All-Cause Mortality•Systematic Review (Flegal, et al. 2013. JAMA)•Hazard ratios for all-cause mortality relative to normal weight (BMI 18.5 <25)•Evaluated self-reported and measured height and weightClassificationHROverweight (BMI 25-30)0.94Obesity (BMI >30) 1.18 Grade 1 (BMI 30-35)0.95 Grade 2-3 (BMI > 35) 1.29What causes obesity?•Generally: –Long-term energy imbalance•Energy in > Energy out•Excess calories and/or lack of physical activityEnergy imbalance effects•Excess energy is stored in fat cells (also called lipocytes or adipocytes) which can enlarge or multiple•Hypertrophy = enlargement of fat cells•Hyperplasia = multiplication of fat cells Having larger fat cells may be worse for disease risk than many smaller fat cells •Over time excesses in energy storage lead to obesityThe cause of this energy imbalance can be due to a number of factors and may vary from person to personAssessment of Obesity1) Weight2) BMI (weight (kg)/ht (m2))3) % body fat-D= mass/volume D of fat= 0.9007 D of fat free mass = 1.100High density = lower % Body fatAssessment of Obesity4) Waist circumference–Visceral fat (fat in abdominal cavity)–Women = > 88 cm, 35 in–Men = >102 cm, 40 in 5) Waist-to-hip ratio–Women: Low <0.8, Mod = 0.81-0.85, high >0.85–Men: Low <0.95, Mod = 0.96-1.0, high >1.0Is BMI good measure of obesity?•Does not differentiate muscle from fat•Why do we use it?Is waist circumference any better?May be a better indicator of body fatFor assessment of likelihood of developing obesity- and overweight-related diseases NHLBI recommends:1) BMI2) Circumference 3) Other risk factors for diseaseTypes of fat•Subcutaneous – Fat directly under the skin•Visceral – “deep fat”, surrounds organs•Abdominal fat = “belly fat” a combination of visceral and subcutaneous•White fat – most of the fat we have •Brown fat – more metabolically –Most babies have brown fatTypes of fatFat depots and diseaseVisceral Adipose Tissue and diseaseBritton, et al. 2013 JACC.Framingham Heart Study, prospective3086 individuals (49% women)Mean age = 50 yearsExposure = Subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), periaortic, pericardial fatOutcome = followed for 5 years, Incidence of CVD, cancer, mortalityVisceral Adipose Tissue and diseaseBritton, et al 2013 JACC.•VAT was associated with incidence of CVD and Cancer, but SAT was not:–CVD: 1.44 in highest tertile of VAT compared to lowest–Cancer: 1.43 in highest tertile of VAT compared to lowest•No type of fat was associated with all-cause mortalityVisceral Adipose Tissue and disease VAT vs. SATVAT has:1) more inflammatory cytokines 2) more adipokines (factors released by fat cells that influence inflammation, metabolism, insulin sensitivity, satiety, vascular function)3) more lipid metabolites4) arterioles display endothelial dysfunctionsummary•How do we define obesity?•Why do we care about studying obesity?•Healthy consequences of obesity•Cause of obesity•Factors associated with obesity•How to assess obesity•Types of fat –Which one is associated with