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'On the Web' is an internet-based supplement that provides additional web content to supplement the material in Concepts of Fitness and Wellness. Browse through the whole document to explore web content related to this concept. If you know the specific 'On the Web' number or page number of the web icon in the text you can click on the direct link you are looking for below. Click here to access the other Online Learning Center resources available from the McGraw Hill Website (http://www.mhhe.com/corbin7e). The material available here is for the exclusive use of students and instructors using the Concepts-based textbooks. All rights reserved (McGraw Hill Higher Education). On the Web - Concept 13Web13-01 - Standards for Body Composition Web 13-03 Underwater Weighing and "Bod Pod" Measures of Body Composition Web13-04: Skinfold Assessment Procedures Web13-05: Bioelectric Impedance Monitors for Estimating Body Fatness Web13-06: BMI as a measure of body composition Web13-07: Fitness Provides Protection against the Health Risks of Obesity Web13-08: Resources on Eating Disorders Web13-09: Female Athlete Triad Web13-10 Metabolic Regulation of Appetite and Body Composition. Web 13-11 Physical Activity and Weight Control Web 13-13 Supplemental Readings Web13-01 - Standards for Body CompositionThe Centers for Disease Control and Prevention have established standards that have assisted public health researchers in monitoring and tracking the epidemic of overweight and obesity. Click here to access the CDC website on definitions of overweight and obesity. The site describes the BMI cutpoints as well as guidelines for waist circumference and other indicators of body fat deposition. While BMI has clear limitations as an indicator of body composition (see Web 15-05) it has provided a valuable tool to follow and track the epidemic of obesity in the country. In the past 10-15 years, the prevalence of obesity (defined as a BMI > 30) has increased by nearly 50%. Prevalence rates have increased from approximately 12% in the early 1990's to over 24% by 2004. The Behavioral Risk Factor Surveillance System (BRFSS) run by the Centers for Disease Control and Prevention (CDC) provides estimates of various health parameters for each state and for many cities across the country. The web site devoted to the BRFSS (http://www.cdc.gov/brfss/) allows users to look at trends over different time periods or even to compare states with respect to obesity or other risk factors. The most recent state map is provided below but users are encouraged to visit the interactive BRFSS site to see other comparisons.  The international trends in most developed countries mirror the trends observed in the United States. Because of this, the World Health Organization (WHO) is essentially viewing the increases in obesity in the world as a true "pandemic". They have recently released a number of important recommendations and guidelines intended to help bring attention to the problem. Read a report on Global Strategy on Diet, Physical Activity and Health from the WHO to better understand the scope of this international effort to address obesity. Web13-02: DEXADual Energy X-ray Absortiometry, or DEXA, is a highly accurate method of measuring body composition and is becoming one of the gold standards in body composition measurement. The test is based on the three component model of body composition testing. The test provides and accurate measurement of total and regional body fat, lean tissue mass, and bone density. DEXA is a non-invasive, very low dose radiation test that requires the subject to lie on the machine for 5 minutes. Several advantages of DEXA testing include: it's not time consuming, there is only a low dose of radiation exposure, and it requires no patient training. The main disadvantage is the cost (up to $300 per person).
Web 13-03 Underwater Weighing and "Bod Pod" Measures of Body CompositionThe most commonly accepted gold standard measurement for body composition assessment is known as "underwater weighing". The procedure is based on Archimedes Principle which states that the buoyant force of an object is equal to the weight of the volume of water that is displaced. Fat because it is less dense occupies a larger volume and therefore has a larger buoyant force. The figure below shows a typical tank used for underwater weighing.  A relatively new device known as the Bod Pod uses the same principle but avoids the problem of having to hold your breath under water. The procedure uses air displacement instead of water displacement to estimate body fatness. The figure below shows a typical BodPod device. For additional information on the Bod Pod visit the following address; http://www.bodpod.com/index.php  Web13-04: Skinfold Assessment ProceduresSkinfold procedures use measurements of subcutaneous fat from different parts of the body to estimate overall body fatness. A larger number of sites theoretically provides the best estimate but requires more time so balance is needed between accuracy and convenience. The Jackson and Pollock (1978), 7-site procedure is one of the more popular assessments for estimating body fatness from skinfolds. Seven different sites from around the body were used to estimate total body fatness. Separate equations were developed for men and women but they both used the same sites (Jackson and Pollock, 1978), The authors later provided evidence that similar validity could be obtained by only using 3 sites and these were different for men and women. (Jackson and Pollock, 1985). Correlations with 7 site procedure were very high (.97) and it was a very strong predictor of body fat measurements from underwater weighing (accounting for 80% of the variance in the actual values. Because of its ease of use and good validity, the 3-site procedure has become a popular assessment technique. Note that the sites differ for males and females to account for differences in body fat distribution. See the comparisons below. Skinfold calipers are now available from a variety of fitness equipment distributors. Calipers range in quality and cost but research has shown that if a person is skilled with skinfold calipers they can obtain accurate information with any type of caliper. Inexpensive plastic calipers can be purchased for under $10 while research quality calipers may cost several hundred. An image of typical plastic calipers is provided below along with images of the two most widely used research calipers (Lange and the Harpenden). The Harpenden skinfold caliper home page provides a variety of resource pages that describe issues with skinfold calipers and body composition evaluations. The website includes equations and images of the most commonly used sites for body composition including the 3 site procedure used in this textbook. The Harpenden caliper is a very precise clinical caliper (considered by some to be one of the most accurate). This level of accuracy may not be needed for personal self-assessments.
Web13-05: Bioelectric Impedance Monitors for Estimating Body FatnessAs described throughout the chapter, there are a number of alternative ways to assess body composition. Many technologically-based techniques have been developed but most are too expensive for use by individuals at home. The price of this technology has come down and efforts have been made by many companies to develop some consumer-based products for body composition assessment. An example is the body composition "scales" that now provide measures of weight and body fat percentage. This procedure is based on resistance to current flow in the body. Electrical conductance is greater in the body if there is more water in the body and the amount of body water is found to be proportional to the amount of lean tissue. Therefore, by measuring resistance to current flow estimates of body fatness can be determined. To complete the assessment, an individual simply stands on the plates and the device provides an output of estimated body fatness based on the measured resistance values. There are a number of sources of error (most notably hydration status) that influence the accuracy of this technique. An image from a product related web site (www.tanita.com) is shown below. Visit the web site to learn more about these products.  Web13-06: BMI as a measure of body compositionThe BMI is widely cited in popular media so it is important to know how it is computed. The BMI is calculated mathematically with the following formula: (weight (kg) / [height (m) * height (m)]. To use English units, multiply your weight in pounds by 703, divide by your height in inches, then divide again by your height in inches. A chart is available in the Lab Resource Materials to allow you to quickly compute your BMI but it is helpful to also know how the number is calculated. There are a number of places on the web that provide information on the establishment of BMI guidelines. The CDC - Growth Chart webpage provides valuable information on healthy ranges of BMI across the lifespan. There are also a number of places that provide interactive BMI calculators and information about healthy body composition.
Web13-07: Fitness Provides Protection against the Health Risks of ObesityThe general assumption in our society is that an overweight or obese person is probably physically inactive and unfit. People also assume that a thin individual is probably physically active, physically fit and healthy. Research on this topic has determined that these generalizations are not accurate. It is clearly possible for overweight individuals to maintain high levels of fitness. Through participation in regular physical activity, it is also possible for overweight individuals to have good health and low risks for chronic disease. Much of this evidence came from some epidemiological studies conducted at the Cooper Institute for Aerobics Research. In one study (Lee, 1999), the researchers studied a population of 21,925 men aged 30-83 who had completed a maximal treadmill tests and body composition assessment as part of a preventive medical visit to the Cooper Clinic. The population was divided by body composition levels into Lean (< 16.7% fat), Normal (16.7-25%) and Obese (> 25) and then subdivided by fitness level into Fit and Unfit categories based on established norms. The individuals were then followed over an average of 8 years to look at various health outcomes. Individuals in the Fit category had lower rates of death (from all causes) than individuals in the Unfit category and this relationship was consistent for all 3 body composition categories. This indicates that fatness is only a risk if a person is also unfit. It also indicates that if a person is thin, they can still be at increased risk if they are not fit. The differences between the groups can be easily seen in the graph below:  The researchers found similar results when the population was divided into categories of waist circumference. See graph below.  In another study, (Wei et al., 1999), researchers categorized individuals from the same population into three different BMI levels (< 25, 25-29.9 and > 30) and then further classified by the presence or absence of different cardiovascular risk factors (e.g. cholesterol, hypertension etc...). The researchers found that low fitness increased the risk of early death, in all body mass index groups even after adjusting for all of the other risk factors. This indicates that being unfit presents additional risks over and above that caused by the other risk factors. The magnitude of the risks for low fitness were also as high or higher than those for the other established risk factors. These findings reveal that that overweight and obese individuals can obtain the same benefits of physical activity as lean individuals. Another way of stating this is that physical activity protects against the health risks potentially caused by overweight or obesity. Sources:
Web13-08: Resources on Eating DisordersEating disorders are a complex problem. The National Institute of Mental Health states the following about eating disorders:
There are a number of different types of eating disorders and prompt diagnosis and referral are critical for successful treatment. While the overall incidence of eating disorders the diagnoses of various conditions has been increasing. Eating disorders are becoming increasingly common among men. The NIMH website provides specific information on the characteristics and prevalence of different eating disorders. Information from the National Eating Disorders Association (http://www.nationaleatingdisorders.org/p.asp?WebPage_ID=337) provides informational links and resources to help people find treatment: Click on the following links to find out more.
Other Web Resources:Eating Disorders Association (United Kingdom-UK) - http://www.edauk.com/ Web13-09: Female Athlete TriadThe female athlete triad is a combination of three related conditions that ultimately end up working in combination to have a negative impact on health. The three components of the triad are disordered eating, amenorrhea and osteoporosis. Experts suggest that internal and external pressures placed on young women to achieve or maintain unrealistically low body weight may underlie the development of the triad. The American College of Sports Medicine (ACSM) has published a position stand on the female athlete triad. They note that participation in sports that emphasize low body weight is a specific risk factor for the condition. Those sports include sports in which performance is subjectively scored (e.g., figure skating, gymnastics); endurance sports emphasizing a low body weight (e.g., distance running); sports requiring body contour-revealing clothing for competition (swimming, diving); sports using weight categories for participation (e.g., horse racing), and sports emphasizing a prepubertal body habitus for performance success (e.g., gymnastics). The position stand can be accessed from the ACSM website (www.acsm.org). Other Web Resources:The Physician and Sports Medicine has an online document that provides an overview of the causes, consequences and treatment of the triad. The American Academy of Family Physicians provides a detailed web-based resource for consumers (www.familydoctor.org). Click here to access the FamilyDoctor link on female athlete triad to learn more. Web13-10 Metabolic Regulation of Appetite and Body Composition.The current view of weight control and energy balance involves a complex feedback loop shown below. This feedback loop involves the brain, fat tissue, and the endocrine system to control hunger signals, food intake, and energy balance. It has been hypothesized that one possible contributor to obesity is resistance to leptin. For additional resources on leptin, consult the following links:  Web 13-11 Physical Activity and Weight ControlAdopting regular habits of physical activity is probably the most important behavior change a person can make to help maintain healthy body fat levels. Consumer Reports conducted a survey of over 32,000 dieters and found that the majority of "successful losers" lost weight on their own rather than using commercial diet plans, meal replacements or dietary supplements. They categorized individuals as "successful losers" if they lost at least 10 percent of their starting weight and kept it off for more than a year. They categorized individuals as "super losers" if they maintained their weight loss for five years or more. A key finding in the study was that exercise was found as the most important strategy for successful weight loss. Those who exercised at least 3 times a week ranked it as the #1 factor in their weight loss success. For additional information, read the CNN Health press release (http://www.cnn.com/2002/HEALTH/05/06/diet/index.html). There is considerable confusion within the general population regarding the amount and type of activity that is beneficial for weight control. One of the most common misconceptions is with the concept of a "fat burning zone". This notion implies that there is a specific range of intensities that is optimal for burning fat and that if you exercise above this intensity you are only burning carbohydrates. While it is true that the body will preferentially use carbohydrates at high intensities this is not important for overall energy balance or weight control. When the body breaks down extra carbohydrates during a workout, the body eventually replaces these energy stores either from food in the diet or from stored fat. The main point is that all of the bodies fuel sources are readily inter-convertible - it doesn't really matter which fuel source is burned as long as calories are expended. The myth of a "fat burning zone" has been popularized by graphs that depict HR zones for different training goals (see below).  This type of graph is often used in health clubs to help people learn about different types of exercise. While it is true that low to moderate intensity exercise is the best recommendation for promoting weight control it is not true that you have to use low intensity exercise to burn fat. ALL exercise will burn calories and therefore fat. Therefore, the graphic shouldn't be interpreted too literally. The reason that low to moderate intensity exercise (heart rates between 120-140) is recommended is because people are able to exercise for a longer time and therefore, burn more calories. However, if you are short on time, vigorous activity can be equally effective since you can burn more total calories in the same amount of time. The key is to find an activity that you enjoy and regularly commit to being physically active over the long term. Many people want to set weight loss goals when they start an exercise program. The problem with this is that exercise can actually lead to weight gain even if significant losses in body fat are taking place. See the diagram below to learn how to calculate a desired body weight based on current body fat percentage and desired body fat percentage. A chart in the book simplifies this calculation but it is useful to understand the concept behind how these calculations are made.  Web13-12: Web ResourcesAmerican Anorexia and Bulemia Association - http://www.aabainc.org/ Fat Control Inc - http://www.fatcontrolinc.org/ FDA Consumer - www.fda.gov/fdac National Center for Health Statistics - www.cdc.gov/nchs North American Association for the Study of Obesity (NAASO) - www.naaso.org Shape up America - www.shapeup.org Web 13-13 Supplemental ReadingsReferences new to 7e/14eCancello, R. et al., 2004. Adiposity signals, genetic and body weight regulation in humans. Diabetes and Metabolism 30: 215-227. Christou, D. D. et al. 2005. Fatness is a better predictor of cardiovascular disease risk factor profile than aerobic fitness in healthy men. Circulation. 111(15): 1904-1914. Dong, L. et al. 2004. Activities contributing to total energy expenditure in the United States: Results from the NHAPS Study. International Journal of Behavioral Nutrition and Physical Activity. Available at: http://www.ijbnpa.org/1/1/4. Esco, M.R., Olson, M.S., Williford, H.N. 2005 Muscle dysmorphia: An emerging body image concern in men27(6): 76-79 Flegal, K.M. et al. 2006. Excess deaths associated with underweight, overweight, and obesity. Journal of the American Medical Association. 293(15): 1861-1867. Franko, D. L., et al. 2005. Food, mood, and attitude: Reducing risk for eating disorders in college women. Preventive Medicine. 24(6): ?? Hills, A. P. et al., 2006. Validation of the intensity of walking for pleasure in obese adults. Preventive Medicine. 42(1): 47-50. Hellmich, N. 2006. Athlete's hunger to win fuels eating disorders. USA Today. February 6: 1A, 6A. Kuk, J.L. et al. 2006. Visceral fat is an independent predictor of all-cause mortality in men. Obesity Research 14:336-341. Levine JA, Lanningham-Foster LM, McCrady SK, Krizan AC, Olson LR, Kane PH, Jensen MD, Clark MM. Interindividual variation in posture allocation: possible role in human obesity. Science 307: 584-586, 2005. Nassis et al. 2005. Aerobic exercise training improves insulin sensitivity without changes in body weight, body fat, adiponectin, and inflammatory markers in overweight and obese girls. Metabolism 54(11): 1472-1479. Ogden, C.L. et al., 2006 Prevalence of overweight and obesity in the United States, 1999-2004. Journal of the American Medical Association 293(13): 1549-1555. Riebe, R. et al. 2005. Long-term maintenance of exercise and healthy eating behaviors in overweight adults. Preventive Medicine. 40(6): 769-778. Winett, R. A. et al., 2005. Long-term weight gain prevention: A theoretically based Internet approach. Preventive Medicine. 41(2): 629-641. Rererences from Past Editions
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