Body Composition

Body Composition Chapter

Body Composition What Is Body Composition and Why Is It Important? Assessing Body Mass Index, Body Composition, and Body Fat Setting Body Composition Goals Making Changes in Body Composition

What Is Body Composition and Why Is It Important? The human body isdivided into fat-free mass and body fat Fat-free mass is body’s nonfat tissues Bone, water, muscle, connective tissue, organ tissues, and teeth

What Is Body Composition and Why Is It Important? Body fat includes essential and adipose tissues Essential fat: Fats incorporated in various tissues of the body, critical for normal body functioning Adipose tissue: Tissue in which fat is stored Subcutaneous fat: Fat located under the skin Visceral fat: Fat located around major organs; also called intra-abdominal fat

FIGURE 6.1Body composition of a typical man and woman, 20–24 years old SOURCE: Adapted from Brooks, G A, et al 2005 Exercise Physiology: Human Bioenergetics and Its Applications, 4th ed New York: McGraw-Hill

Overweight and Obesity Defined Most important consideration: proportion of body’s total weight that is fat Percent body fat: The percentage of total body weight that is composed of fat Overweight: Body weight that falls above the recommended range for good health; sometimes defined as a body mass index between 25 and 299

Overweight and Obesity Defined Obesity: Severely overweight, characterized by an excessive accumulation of body fat; may also be defined in terms of some measure of total body weight or a body mass index of 30 or more

Prevalence of Overweight and Obesity Among Americans Prevalence of obesity increased from 13% in 1960 to 35% today 68% of adult Americans overweight About 35.5% of men and 35.8% of women obese, according to the latest statistics By 2015, estimates are that 75% of adults will be overweight and 41% will be obese

Prevalence of Overweight and Obesity Among Americans Possible explanations: More sedentary work and leisure activities Fewer short trips on foot and more by automobile Fewer daily gym classes for students More meals eaten outside the home Greater consumption of fast food Increased portion sizes, and more soft drinks and convenience foods

FIGURE 6.2Trends in overweight and obesity in adults age 20 and older, by sex, in the U.S., 1988–1994,1999–2002, and 2007–2010 SOURCE: Centers for Disease Control and Prevention and the National: enter for Health Statistics 2011 2007–2010 National Health and Nutrition Examination Survey (NHANES) Hyattsville, Md: National Center for Health Statistics

FIGURE 6.3Prevalence of obesity and trends in the distribution of body mass index among U.S. adults, 2010 SOURCE: Flegal, K M, et al 2012 Prevalence of obesity and trends in the distribution of body mass index among US adults, 1999–2010 Journal of the American Medical Association 307(5): 491–497

Metabolic Syndrome, Diabetes, and Premature Death Metabolic syndrome: Cluster of symptoms present in many overweight and obese people that greatly increases their risk of heart disease, diabetes, and other chronic illnesses; symptoms include insulin resistance, abnormal blood fats, abdominal fat deposition, type 2 diabetes, high blood pressure, high blood glucose, and chronic inflammation

Metabolic Syndrome, Diabetes, and Premature Death Chronic inflammation: A response of blood vessels to such harmful substances as germs, damaged cells, or irritants; can lead to heart disease, cancer, allergies, and muscle degeneration

Body Fat Distribution and Health Distribution of body fat is an important indicator of health Apple shape versus pear shape Abdominal fat is more easily mobilized and sent into bloodstream, increasing disease-related blood fat levels Waist circumference helps assess risks of unhealthy body fat distribution

Performance of Physical Activities Too much body fat makes physical activity difficult Overfat people are less fit than others and lack muscular strength, endurance, and flexibility that make normal activity easy

Emotional Wellness and Self-Image Being perceived as fat can be a source of ridicule, ostracism and can contribute to psychological problems The popular image of the “ideal” body has changed greatly in the past 50 years

Problems Associated with Very Low Levels of Body Fat Health experts generally view too little body fat as a threat to health Too little for women: less than 8 to 12% Too little for men: less than 3 to 5%

Problems Associated with Very Low Levels of Body Fat Amenorrhea: Absent or infrequent menstruation, sometimes related to low levels of body fat and excessive quantity or intensity of exercise Female athlete triad: A condition consisting of three interrelated disorders: abnormal eating patterns (and excessive exercising) followed by lack of menstrual periods (amenorrhea) and decreased bone density (premature osteoporosis)

Calculating Body Mass Index Body mass index (BMI): Measure of relative body weight correlating highly with more direct measures of body fat, calculated by dividing total body weight (in kilograms) by the square of body height (in meters) BMI between 18.5 and 24.9 considered healthy

TABLE 6.1Classifications from theWorld Health Organization

Estimating Percent Body Fat Underwater Weighing Individual submerged and weighed under water Percentage of fat and fat-free weight calculated from body density The Bod Pod Small chamber containing computerized sensors measures body composition by air displacement

Estimating Percent Body Fat Skinfold Measurements Typically involves measuring thickness of skinfolds at different places on the body Caliper: A pressure-sensitive measuring instrument with two jaws that can be adjusted to determine thickness Important to test exact sites, to measure several different times, and to take measurements at approximately the same time of day

Estimating Percent Body Fat Bioelectrical Impedance Analysis (BIA) Works by sending a small electrical current through the body and measuring the body’s resistance to it Advanced Techniques: DEXA and TOBEC DEXA works by measuring tissue absorption of high- and low-energy X-ray beams TOBEC estimates lean body mass by passing a body through a magnetic field

TABLE 6.2Percentage of Body Fat asthe Criterion for Obesity

Assessing Body Fat Distribution Waist circumference measurement and waist-to-hip ratio calculation easiest to perform Total waist measurement more than 40 inches for men and 35 inches for women and a waist-to-hip ratio above 0.94 for young men and 0.82 for young women are associated with increased risk of heart disease and diabetes

Somatotype Endomorphs are round and pear shaped, with wide hips and shoulders Mesomorphs are lean and muscular and respond well to exercise Ectomorphs are thin and linear, with narrow hips and shoulders

Setting Body Composition Goals If assessment tests indicate that fat loss would be beneficial, first step is to establish a realistic goal Be sure your goal is realistic and will ensure good health

Setting Body Composition Goals If you are overfat or have known risk factors, consult a physician to determine a body composition goal for your individual risk profile Decide whether the body weight the formulas suggest is realistic, meets your goals, is healthy, and is reasonable to maintain

Making Changes in Body Composition Focus on lifestyle Track progress Reassess your body composition occasionally during the program

Body Composition