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Student%20Lecture%2018%20%28Obesity%20and%20Inactivity%29 -...

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Unformatted text preview: Lecture 18 Obesity and Inactivity Obesity Tuesday 3­23­10 • • Extra Credit – Proof of completion of online course evaluation. Due 5­7­10. – Proof of attending a Purdue Sporting event (ticket stub and picture) plus ½ page summary of applying concept learned in HK368 to what you observed. Due 5­7­10. – Ultrasound practice subject. Contact: [email protected] Monday and Friday – 8:30am to 12:30pm Tuesday and Thursday – 9:30am Wednesday – 8:30am to 11:30am – Seminar – April 14th, 3:30pm, Armstrong 1109 Quiz #10 Lecture – Obesity and Inactivity Discuss Grant Assignment #4 Outline Outline Obesity Trends* Among U.S. Adults BRFSS, 1990, 1998, 2007 (*BMI ≥ 30, or about 30 lbs. overweight for 5’4” person) 1990 1998 2007 No Data 29% <10% ≥30% 10%–14% 15%–19% 20%–24% 25%– Center For Disease Control Obesity in the United States Obesity NHANES Survey 2006 – Men Obese (BMI>30) – Women Obese (BMI>30) – Children (ages 2­19) Obese (95 percentile of BMI for growth charts) – Overweight Obesity Comparison Between US and Europe and Europe United States Center For Disease Control Top 10 most Obese and Leanest Countries (World Health Organization) Countries 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Tonga (56%) French Polynesia (41%) Saudi Arabia (36%) United Arab Emirates (34%) USA (32%) Bahrain (29%) Kuwait (29%) Seychelles (25%) UK (24%) 1. 2. Lao (1%) 3. Gambia (2%) 4. Indonesia (2%) 5. Korea (2%) 6. China (3%) 7. Japan (3%) 8. Ghana (3%) 9. Eritrea (3%) 10. Pakistan (3%) Effects of Obesity on Chronic Disease Disease Obesity is linked to – – – – – – – Burden on the health care system – Diabetes billion dollars in 1998 McArdle, Katch and Katch Effects of Obesity on Relative Risk of Death in Healthy Individuals of What are the factors contributing to the increase in obesity? the Percentage of Americans Meeting the Recommended Amount of Physical Activity in 2007 Physical Recommended physical activity is defined as at least 5 days a week of at least 30 minutes a day of moderate intensity exercise or 3 days a week of 20 minutes a day of vigorous intensity exercise. Center For Disease Control Effects of Physical Inactivity on Chronic Disease Chronic premature deaths each year due to physical inactivity (WHO) in United States attributed to physical inactivity in 1986 (CDC). Physical inactivity attributed to more than chronic diseases (Booth 2003) Frank Booth has coined this the “ ” Neel’s Thrifty Gene Hypothesis Neel’s – Genome of humans were developed under conditions that required physical activity for survival (i.e. hunter gatherers and agrarians). Physical activity declined significantly during the . Genetic evolution has not changed as rapidly as . Modern man is living in a modern society with prehistoric genes. Examples of reductions in physical activity in our society activity Energy expenditure Television watching in children – 1950 – hours per week – 2000 – hours per week – Hunter gatherers kcal/kg/day – Office workers kcal/kg/day Amish vs. Average (Bassett 2004) – Amish Children ( steps) v. Average ( steps) Flohr 2006 – Amish Adults ( steps) Average ( steps) Amish Overweight % vs. Average % Amish Obese % vs. Average % Amish Overweight % Amish Obese % vs. Average % Methods of Determining Body Composition Body Body mass index (BMI) – – Percentage above recommended weight Problems with these methods – No way to tell actual body composition A very muscular person could be classified as obese BMI Classification BMI < 18.5 Normal 25.0­29.9 Obesity – Class I 30.0­34.9 Obesity – Class II Extremely Obese–Class II ≥ Isotope Dilution Photon Absorptiometry Potassium­40 Near Infrared Interactance (NIRS) Radiography Ultrasound Nuclear Magnetic Resonance (NMR) Total Body Electrical Conductance Body Composition Measurement Measurement Hydrostatic Weighing Hydrostatic Archimedes’ Principle Density – H2O g/ml – Fat g/ml – Muscle g/ml Calculate body fat based on weight on land, in water and residual lung volume. Disadvantages – McArdle, Katch and Katch Dual Energy X-Ray Absorptiometry (DEXA) (DEXA) 2 distinct X­ray beams (low radiation) 30 cm depth penetration Scan rate 1cm/sec Results – – – http://hes.cahs.colostate.edu/ResearchLabs/IntegrativeBiologyLab/ http://www.gorhams.dk/html/what_is_dexa_scanning.html Strong Correlation between DEXA and Hydrostatic Weighing McArdle, Katch and Katch Bioelectrical Impedance Analysis Bioelectrical Measures the time for electrical current to pass from one extremity to another. How would dehydration affect results? McArdle, Katch and Katch Air Displacement Plethysmography Air BOD-POD Measures pulmonary gas volume which are then subtracted from body volume measurements. McArdle, Katch and Katch Strong Correlation between BOD POD and Hydrostatic Weighing McArdle, Katch and Katch Skinfold Thickness Skinfold Thickness of subcutaneous fat is measured – Body density is calculated using specific equations – Percent body fat calculated from body density What are the disadvantages and advantages of this technique? McArdle, Katch and Katch Skinfold Thickness Sites Skinfold McArdle, Katch and Katch Strong Correlation between Skinfolds and Hydrostatic Weighing McArdle, Katch and Katch Standard Values of Percent Body Fat Standard McArdle, Katch and Katch Why are standards for body fat higher in women then in men? higher McArdle, Katch and Katch Fat Cells Fat billion fat cells in normal individuals billion fat cells in obese individuals Hypertrophic obesity – – Hyperplastic obesity Increase in Increase from kg of body fat McArdle, Katch and Katch – Increase in – Increase from kg of body fat – Reduced ability to lose and maintain weight loss. Figure 18.3 Set Point Theory Set The tendency of a person to return to a certain weight suggests that there is a biological set point for body weight, much like the set points for any negative feedback biological control system Physiological Cognitive Figure 18.4 Figure 18.5 Nutrient Balance Nutrient energy balance – Increase intake of kcals•day­1 would lead to pound weight gain over one year change of = energy stores energy expenditure Nutrient Balance Nutrient energy balance – Increase in energy intake results in increased body weight – Energy expenditure also increases and weight is maintained at a new, higher level – Results in weight gain of only pounds in a year rate of change rate of change of = of energy stores energy intake What are the three componenets of energy expenditure? energy Basal Metabolic Rate (BMR) Basal – Supine position, immediately after rising, 12­18 hours following a meal – Similar to resting metabolic rate (RMR) – Lower in , declines with – Related to Represents % total energy expenditure Reduced in response to reduced caloric intake (dieting or fasting) – Exercise can maintain BMR Thermogenesis Thermogenesis “ ” associated with: Not associated with obesity – Ingestion of meals (thermic effect of feeding) Physical Activity Physical Accounts for – Depends on activity level Important in determining obesity – Figure 18.8 Effect of Exercise on Appetite Effect Most humans – – Maintains body weight Formerly sedentary individuals – – Facilitates weight loss Figure 18.10 Exercise and Body Composition Exercise Individuals who exercise generally have lower body weight and percent fat Weight loss in conjunction with exercise – – McArdle, Katch and Katch Study: Genetics and Obesity Study: Bouchard et al. 1990 12 pairs of twins 1000 calories per week in excess of baseline energy requirements Differences in body mass change between twin pairs exceeded differences within twin pairs. Correlation within twins suggests a genetic component to weight gain. McArdle, Katch and Katch Study: Nonexercise activity thermogenesis (Levine et al, 1999) thermogenesis 18 nonobese subjects 1000 kcals excess per day 8 weeks Increase in body fat correlated with nonexercise activity thermogenesis (NEAT) Study: Effects of Weight Gain on Walking (Levine et al. 2008) Walking Subjects – 10 lean, 12 obese 1000 kcals excess per day 8 weeks Increase in body fat decreased walking distance. ...
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