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  • 2 This lecture will cover the subject of body composition. Students will learn about the different assessment techniques and how body composition influences health.
  • Body composition generally considered to be a health-related component of physical fitness. However, body composition is unlike the other parts of health-related physical fitness in that it is not a performance measure. Cardiovascular fitness, strength, muscular endurance, and flexibility can be assessed using movement or performance, such as running, lifting, or stretching. Body composition requires no movement or performance. This is one reason some experts prefer to consider body composition as a component of metabolic fitness. Whether you consider body composition to be a part of health-related or metabolic fitness, it is an important health-related factor. Assessing body weight too frequently can result in making false assumptions about body composition changes. The most common way that people gauge their body composition is by periodic assessments of body weight. While occasional checks of weight (and BMI) can be helpful, frequent body weight measurements can provide incorrect information and lead to false assumptions. For example, people vary in body weight from day to day and even hour to hour, based solely on their level of hydration. Short-term changes in weight are often due to water loss or gain, yet many people erroneously attribute the weight changes to their diet, a pill they have taken, or the exercise they recently performed. Monitoring your weight less frequently—once a week, for example—is more useful than taking daily or multiple daily measures because doing so is more likely to represent real changes in body composition. Weighing at the same time of day, preferably early in the morning, is best because it reduces the chances that your weight variation will be a result of body water changes. Of course, it is best to use body composition assessments in addition to those based on body weight if accurate evaluations are expected.
  • 3 A variety of techniques have been developed to measure body composition. Each will be discussed in greater detail so use the slide as a general introduction to the area.
  • 4 Underwater weighing was formerly the gold standard measure of body composition. It is based on the fact that muscle is more dense than fat - muscle is like a rock (it sinks) - fat is like styrofoam (it floats) By weighing a person underwater you can estimate body density. The procedure is based on Archimedes Principle which states that the buoyant force is equal to the weight of the volume of water that is displaced. Fat because it is less dense occupies a larger volume which gives it a larger buoyant force NOTE: The story of Archimedes and the gold crown is effective for explanation (muscle = gold and fat = silver)
  • 6 The technique is called skinfold because a fold of skin is picked up and measured. Underneath the skin the body stores subcutaneous fat so when the skin is lifted the fat layer can be measured. Body fat is stored in people in different places and the measurement of fat in one place is not always an accurate measure of total body fat. Also, the thicknesses must be converted into a meaningful measure (% body fat). This is done using a statistical procedure called multiple regression. Discuss procedure (optional): Body fat is measured with a very accurate technique and then the various skinfold sites are used to predict the overall percent body fat as assessed by the criterion measure..
  • 7 Skinfold Technique is the most common way to assess body fat. It has the following advantages: - fairly accurate - easy to perform - inexpensive
  • 8 7 site procedure was originally developed and different weights were put on different sites for men and women Separate equations were developed for men and women but they both used the same sites. (1978) In general, the more skinfolds measured, the more accurate the fatness estimate. However, measurements with two or three skinfolds have been shown to be reasonably accurate and can be done in a relatively short period. The authors later provided evidence that similar validity could be obtained by only using 3 sites and these were different for men and women. (1985). Correlations with 7 site procedure were very high (.97) and it was a very strong predictor of body fat measurements from underwater weighing. Now, if any of you have ever done testing you know that there are certain sites that are more difficult than others. What is toughest site for women? men? They have also provided alternative 3 site procedures for both men and women men: subscapular substituted for abdomen women: abdomen substituted for thigh For children, we use a 2 site procedure that includes the calf and the tricep. This is from the Fitnessgram program (www.fitnessgram.net)
  • The two most common types of skinfold calipers are the Harpenden and the Lange calipers. Experts can notice the increased precision of quality calipers but studies have shown that inexpensive plastic calipers can yield accurate results if used correctly.
  • 5 Other body fat assessment techniques are available. Bioelectric Impedance: Electrical conduction is different in different tissues. Muscle has water and is a good conduction. Fat has less water and is a poor conductor. It tends to overestimate %fat in lean people and underestimate %fat in fat people. Infra Red Absorption of light is different in different tissues. Ultrasound Sound absorbance is different in different tissues (muscle: sounds bounces off; fat: sounds pass through) Imaging Techniques (DEXA, MRI) Considered to be highly accurate but expensive Chemical measures (3 methyl histidine - waste product of muscle - corr with LBM
  • 12 It is difficult to get body fat measures on all people so in many occasions anthropometric measures are still effective ways to obtain information about body composition.
  • 11 Body Fat estimates from calipers must be interpreted correctly. It is important to keep the following factors in mind: 1. The estimates have 2-3% error so the value that results is not "exact". It is more important to look at trends over time. 2.Values serve as baseline for goal setting. You need to know where you are to set objective goals. Book has a chart to calculate desired weight based on current level and desired level (formula available from instructor). 3. Values are individual. People should not compare values with other people or be embarrassed about their numbers. Each person is different and it may not be possible for all people to achieve the ideal percent body fat.
  • 5 Many health problems are associated with excess levels of body fatness Obesity is considered to be a secondary risk factor for coronary heart disease mainly because the effect of body fatness is manifested in other risk factors. These data show the relative risk of other risks if you are overfat (data from NHANES II data cited in VanIttallie (1992): Hypertension (RR = 2.9x) Hypercholesterolemia (RR = 1.5x Diabetes (RR = 2.9x) VanIttallie, T. B. (1992) Body Weight, Morbidity, and Longevity. IN: Bjorntorp, P. & Brodoff, B.N. (Eds.) Obesity. Lippincott Co.., Philadelphia.
  • 9 The site of fat deposition is also an important consideration for health. Fat stored in the abdominal region presents more risk than fat stored in the lower or upper extremities. The location of body fat can influence the health risks associated with obesity. Fat in the upper part of the body is sometimes referred to as “Northern Hemisphere” fat, and a body type high in this type of fat is sometimes called the “apple” shape. Upper body fat is also referred to as android fat because is it is more characteristic of men than women. Postmenopausal women typically have a higher amount of upper body fat than premenopausal women. Lower body fat, such as in the hips and upper legs, is sometimes referred to as “Southern Hemisphere” fat. This body type is sometimes called the “pear” shape. Lower body fat is also referred to as gynoid fat because it is more characteristic of women than men.
  • In Western society, the near obsession with thinness has been, at least in part, responsible for eating disorders. Eating disorders, or altered eating habits, involve extreme restriction of food intake and/or regurgitation of food to avoid digestion. The most common disorders are anorexia nervosa, bulimia, and anorexia athletica. All of these disorders are most common among highly achievement-oriented girls and young women, although they affect virtually all segments of the population. Patterns of “disordered eating” are not the same as clinically diagnosed eating disorders. People who adopt disordered eating, however, tend to have a greater chance of developing an eating disorder.
  • Regulatory processes appear to balance energy intake and energy expenditure so that body weight stays near a biologically determined set-point. The regulation is helpful for maintaining body weight but can be frustrating for people trying to lose weight. If a person slowly tries to cut calories, the body perceives an energy imbalance and initiates processes to protect the current body weight. The body can accommodate to a new, higher set-point if weight gain takes place over time, but there is greater resistance to adopting a lower set-point. Many people lose weight only to see the weight come back months later. One of the reasons that exercise is so critical for weight maintenance is that it may help in resetting this set-point.
  • This page provides active hyperlinks if the computer is connected to the Internet.
  • Supplemental graphics follow this slide.
  • Lab information
  • 9 This diagram shows the technique that is used in skinfold analysis. Go through steps. It takes a lot of practice to get very good at the technique but it can be done in class so students get an idea of how the technique is performed. If time is limited ask for a volunteer to serve as a subject for a class demonstration.
  • Lab information
  • 15 Review procedure for the calculation of BMI
  • 13 Explain the calculation of WHR
  • 16 Figure shows sample BMI values for a hypothetical 6 foot person of different body weights. This helps students see how the values change for people of different sizes.
  • 15 BMI is an alternative procedure to identify overweight conditions based on height and weight. BMI provides a slightly more accurate assessment of body composition than simple height/weight charts but the same bias is present. People with a large LBM will have a high BMI value even if their body fat level is low. Review procedure for the calculation of BMI
  • Lab 13c
  • 9 The site of fat deposition is also an important consideration for health. Fat stored in the abdominal region presents more risk than fat stored in the lower or upper extremities
  • There are many studies that document the health risks associated with abdominal obesity.
  • These are some additional studies that document the health risks of abdominal obesity
  • 14 Review health consequences associated with abdominal body fat
  • Underwater weighing is based on body density calculations. The density of lean tissue is greater than the density of fat tissue. Underwater weighing, while it is considered to be the gold standard, does have considerable measurement error and still must be classified as an estimate. Residual lung volume is a major source of error. For an accurate assessment a person must exhale all of their air and remain still enough for a person to accurately read the value. Some people cannot hold their breath under water or get claustrophobic and come up too soon. Even if you exhale all of your air there is still some residual volume of air in your lungs that you cannot remove. This has to be measured in an additional test that has its own levels of errors. When estimates of residual volume are made then the tests have still higher errors. Body density values vary by age, ethnicity, and activity level. Most calculations do not take those variables into account which can lead to erroneous values. Blacks have higher bone density - underprediction (2% unreal) children have lower bone density - overprediction A difference of .015 g/cc in density estimate can lead to a 4-5% error in % fat
  • Bioelectric impedance is based on differential resistance to current flow Because it is actually providing an estimate of total body water which is then used to predict body fatness the test is very sensitive to hydration status. The test will generally overestimate lean people and underestimate obese people So the relationship with measured percent body fat is really curvilinear rather than linear
  • Infrared spectroscopy is a fairly new procedure that you will see in many health clubs. It looks great and they have good marketing for the product but when you come right down to it the procedure really doesn’t work - at least in the way that they claim. The procedure was originated in the agriculture field where they would use it to determine the quality of different cuts of meats. They take a little light gun and shine and infrared light beam into your biceps and measure the amount of light reflected back to the sensor after it has been somewhat absorbed by the body. Show the overhead of the faulty readings
  • Ultrasound is a highly accurate technique but it is typically only used in hospital or clinical settings.
  • Imaging techniques provide a valid assessment but are very expensive. This is typically only done in laboratory or clinical settings.
  • Circumferences have commonly been used. I included a reference for a circumference procedure that you might be interested but in my opinion they are not as accurate as skinfolds and take just as much time so there is really no advantage. Some people will want to measure circumferences to monitor changes in muscle size but skinfolds are certainly a better way to assess b ody fatness.

Transcript

  • 1. Presentation Package for Concepts of Physical Fitness 14e Section V: Concept 13 Body Composition Possessing an optimal amount of body fat contributes to health and wellness. All rights reserved
  • 2. Understanding & Interpreting Body Composition Measures
    • Component of health-related fitness & a component of metabolic fitness.
    • Standards have been established for healthy levels of body fatness (see next slide)
    • Health standards have been established for the Body Mass Index.
    • Assessing body weight too frequently can result in making false assumptions about body composition changes.
  • 3.  
  • 4. Methods Used to Assess Body Composition
    • DXA
    • Underwater Weighing
    • Bod Pod
    • Skinfold technique
    • Other
  • 5. Dual-energy Absorptiometry (DXA)
    • “ Gold Standard” measure of body composition.
    • Provides whole body measurements of body fatness as well as amounts stored in different parts of the body.
    • Highly accurate measure of body composition for research and a criterion measure that has been used to validate other, more practical measures of body composition.
  • 6. Underwater Weighing Click for more info Web13-3 for info on underwater weighing
    • A person is weighed in air and under water, and the difference in weight is used to assess the levels of body fatness.
    • Body fat provides more buoyancy, so a fatter person weighs less (on a relative basis) than a lean person.
  • 7. Bod Pod
    • Uses the same principles as underwater weighing, but relies on air displacement to assess body composition.
    • Evidence suggests that it provides an acceptable alternative to underwater weighing and is particularly useful for special populations (obese older people and the physically challenged).
  • 8. Skinfold Technique Layers of subcutaneous fat are measured at different sites of body to estimate total body fat levels Cross sectional view
  • 9. Benefits of Skinfold Technique
    • Skinfold measurements are the preferred, practical method of assessing body fatness.
    • Fairly accurate
    • Easy to perform
    • Inexpensive
    Lab 13a info
  • 10. Common Skinfold Sites
    • 7 site procedure
      • Chest
      • Axilla
      • Tricep
      • Subscapular
      • Abdomen
      • Supraillium
      • Thigh
    Jackson and Pollack Males Female Chest Triceps Abdomen Supraillium Thigh Thigh Validation statistics on 3 site test: - r = .97 with 7 site procedure - R 2 = .80 with underwater weighing Alternative Sites (Males & Females) Tricep Abdomen Calf Web13-04
  • 11. Research Quality Skinfold Calipers Harpenden Calipers Lange Calipers
  • 12. Other Body Composition Assessments
    • Bioelectrical Impedance
    • Infra-Red Spectroscopy
    • Ultrasound
    • Imaging Techniques
    Click to see more info on all techniques
  • 13. Anthropometric Measurements
    • Body Mass Index (BMI)
    • Waist to Hip Ratio (WHR)
    • Circumference measures
    More info More info More info Lab 13b info
  • 14. Body Composition Assessment Implications of Results
    • Values are estimates (+/- 2-3% at best)
    • Values are personal and confidential
    • Proper uses of results:
    • - Serve as baseline data for repeated testing
    • - Provide motivation for goal setting
    • - Provide awareness about health risks
  • 15. Health Risks Associated with Being Overweight
    • Coronary heart disease
    • Hypertension
    • Hypercholesterolemia
    • Diabetes
    • Premature death
    • Physical fitness provides protection from the health risks of obesity.
    There are also health risks associated with being too thin!
  • 16. Regional Fat Deposition
    • Abdominal body fat poses greater health risks than fat stored in other areas
    • Males store more fat centrally and have increased health risks associated with body fatness
    Click for more info on fat deposition Higher health risk Lower health risk Male (apple) Female (pear)
  • 17. Health Risks Associated with Excessively Low Body Fatness
    • Anorexia Nervosa
    • Bulimia
    • Anorexia Athletica
    • Female Athlete Triad
    • Muscle Dysmorphia (males)
    • Fear of Obesity
  • 18. The Origin of Fatness
    • Obesity is a multifactorial disease that is influenced by both genetics and the environment.
    • Body weight is regulated and maintained through complex regulatory processes.
      • Set-point
    • Fatness early in life leads to adult fatness.
    • Changes in basal metabolic rate can be the cause of obesity.
    • “ Creeping Obesity” (see next slide)
    Lab 13c info
  • 19.  
  • 20. Relationship Between PA & Body Composition
    • Combination of regular PA and dietary restriction is the most effective means of losing body fat .
    • PA that can be sustained for relatively long periods is considered the most effective for losing body fat.
    • Strength training can be effective in maintaining a desirable body composition.
    • Regular PA is critical for building and maintaining bone health.
  • 21. Target Zone - Body Fat Reduction Table 3, p. 285
    • Physical Activity
    • Daily moderate PA; 3-6 days/wk vigorous PA
    • Slow, low-intensity that results in ≤1-2 lbs/week of fat loss
    • 30-60 minutes
    • Diet
    • Consistently and daily
    • Modest caloric restriction
    • Moderate meals
    F I T
  • 22. 1995 Obesity Trends* Among U.S. Adults BRFSS, 1990, 1995, 2005 (*BMI  30, or about 30 lbs overweight for 5’4” person) 2005 1990 No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%
  • 23. Web Links
    • Behavioral Risk Factor Surveillance System (BRFSS) Interactive Web Page
    • http://www.cdc.gov/brfss/
  • 24. Summary
    • Obesity is prevalent in society.
    • Need to find ways to maintain optimal body composition.
    • Use assessments to determine body composition and make the necessary healthy changes to physical activity and diet.
  • 25. Web Resources “ On the Web” pages for Concept Online Learning Center
  • 26. Supplemental Graphics
    • Lab Information
    • Detail on BMI calculations
    • Graphics on Obesity Trends
  • 27. Lab 13a Information Evaluating Body Composition - Skinfolds
    • The purpose of this lab is to evaluate body composition with the skinfold assessment.
    • Comparisons will be made between different procedures and testers to learn about the accuracy of the tests.
  • 28. Lab 13a Information Skinfold Technique
    • Measurement Technique:
      • Mark site with marker
      • Pinch fold above and below mark with left and right hand
      • Measure fold with caliper using the right hand
    • Scoring Procedure:
      • Sum skinfolds from the 3 sites
      • Look up percent body fat value from chart in the book
    Return to presentation
  • 29. Lab 13b Information Evaluating Body Composition – Height, Weight, and Circumference Measures
    • The purpose of this lab is to evaluate body composition with some anthropometric assessments
      • Height/Weight
      • Body Mass Index
      • Waist to Hip Ratio
  • 30. Lab 13b Information BMI Measurement Technique
    • Convert weight to kilograms (2.2 kg/lb.)
    • Convert height to meters (.0254 m/in)
    • Square the height in meters
    • Divide the squared height value into the weight value
    BMI = Wt (kg) / Ht 2 (m) Return to presentation See Web13-06 for BMI calculators
  • 31. Lab 13b Information WHR Measurement Technique
    • Waist: Measure at the &quot;natural waist&quot; (smallest circumference) or at the level of the umbilicus
    • Hip: Measure at the maximum circumference of the buttocks
    Divide the hip measurement into the waist measurement to obtain the WHR Return to presentation
  • 32. Sample BMI Values This chart reveals how BMI values change for a hypothetical 6 foot tall person of different body weights See Web13-06 for BMI calculators Return to presentation HT (in.) WT (lb.) BMI 72 150 21 72 180 25 72 190 26 72 200 28
  • 33. Definitions of Overweight (Based on BMI values)
    • BMI accounts for differences in frame size better than height weight tables. BMI = Wt (kg) / Ht 2 (m)
    • Standards:
      • Overweight: > 25
      • Obesity: > 30
      • Severe obesity > 40
    Problem: BMI does not take muscles mass into account Web13-1 for more information on standards Return to presentation
  • 34. Lab 13c Information Determining Your Daily Energy Expenditure
    • Estimate your basal metabolism.
    • First determine the number of minutes you sleep.
    • Monitor your activity expenditure for 1 day. Record the number of 5-, 15-, and 30-minute blocks of time you perform each of the different types of physical activities (e.g., if an activity lasted 20 minutes, you would use one 15-minute block and one 5-minute block). Be sure to distinguish between moderate (Mod) and vigorous (Vig) intensity in your logging.
    • Discuss your daily caloric expenditure. In addition, comment on whether you think you should modify your daily caloric expenditure for any reason.
    Return to presentation
  • 35. Regional Fat Deposition Visceral Fat
    • Visceral body fat poses greater health risks because this fat is more labile and has greater access to the circulation.
    • The accumulation of visceral body fat is typical of the android (male) fat pattern
      • males: visceral accounts for 10-35% of total fat
      • females: visceral accounts for 8-13%of total fat
  • 36. Abdominal Body Fat Relationships with CHD Risks
    • Abdominal obesity predicts CHD risk independent of BMI, smoking, cholesterol and hypertension. (Kannel et al., J. Clin Epid., 44, 183-190, 1991).
    • Abdominal obesity predicts CHD risk independent of total body fatness. (Larsson et al. ,Appetite, 13, 37-44, 1989).
    • Abdominal obesity statisticallly accounts for difference in CHD rates between men and women. (Larsson et al., Am. J. Epi., 135: 266-273, 1992).
  • 37. Abdominal Body Fat Relationships with other risk factors
    • Abdominal obesity is strongly influenced by genetics - similar gain among twins (r=.72). (Bouchard, NEJM, 322, 1477-1482, 1990).
    • Abdominal obesity is greater in smokers than non-smokers due to the presence of androgens (Barrett-Conner, Ann. Int. Med. 111, 783-787, 1989).
    • Abdominal body fat is preferentially lost during a physical activity program (Kohrt, J. Gerontology, 47: M99-M105, 1992)
  • 38. Waist to Hip Ratio (WHR)
    • Waist to Hip Ratio is an effective way to examine regional fat distribution.
    WOMEN MEN High Risk Moderate Risk Low Risk > 1.0 > .85 .90 -1.0 .80-.85 HEALTH RISK < .90 < .80 Return to presentation
  • 39. Underwater Weighing Measurement issues
    • Based on body density calculations
      • Density of lean tissue = 1.1 g/cc
      • Density of fat tissue = .9 g/cc
    • Sources of error
      • Residual lung volume
      • Bone density varies by age, ethnicity and activity level
    • General conclusions
      • Gold standard measure (1-2% error)
      • Impractical for most applications
    Return to presentation
  • 40. Bioelectric Impedance (Measurement Issues)
    • Based on resistance to current flow
      • Lean tissue has more water - less resistance
      • Fat tissue has less water - more resistance
    • Sources of error
      • Temperature
      • Hydration status
    • General conclusions
      • Overestimates lean / underestimates obese
      • Practical, but expensive, measure for general population
    Return to presentation
  • 41. Infrared Spectroscopy (Measurement Issues)
    • Based on differential absorbance rates
      • Lean tissue has a different energy absorption and reflectance pattern than fat tissue
    • Sources of error
      • Validity of absorbance readings is questionable!
    • General findings
      • NOT a valid measure!
    Return to presentation
  • 42. Ultrasound (Measurement Issues)
    • Based on reflection of sound
      • Fat content increases the time is required for sound to reflect off of bone and muscle.
    • Sources of error
      • Representative sites for measurement
      • Measurement error
    • General conclusions
      • Highly accurate measure of body fat - especially for obese
      • Expensive and not practical for most applications
    Return to presentation
  • 43. Imaging Techniques (Measurement Issues)
    • Based on imaging of body tissues
      • Based on cross sectional area measures calculated at different levels of the body
    • Sources of error
      • Representative sites for measurement
      • Measurement error
    • General conclusions
      • Very precise measure of body composition
      • Expensive and not practical measure for most uses
    Return to presentation
  • 44. Circumferences (Measurement Technique)
    • Based on circumference measures
      • sample prediction equation: % fat = - 47.372 + (.579 x abdomen) + (.252 x hip) + (.214 x iliac) + (.356 x BW)
    • Sources of error
      • Location of sites
      • Inability to distinguish fat and muscle
    • General conclusions
      • Provides reasonable estimate of body fat
      • Not as accurate as skinfold and takes same time
    Return to presentation