Chapter 7 Body composition basics

COMING UP IN THIS CHAPTER Understand the basic composition of your body Identify factors that influence your body composition Examine the relationship between body composition and health Assess your body composition Identify strategies for making changes in your body composition

Basics of Body Composition What is body composition? Body composition: the makeup of the body The relative proportions of different types of body tissues Muscle Bone Fat Other vital tissues Percent body fat is the measure most often used to define and evaluate body composition

Basics of Body Composition Is there such a thing as good body fat? The body needs fat in order to function Essential fat Found in the central nervous system, bone marrow, various organs Surrounds nerve fibers in the brain allowing for the transmission of messages Key component of cell membranes Important in healthy hormone production 8–12 % in females and 3–5 % in males More…

Basics of Body Composition Storage fat (adipose tissue) Site for storage of energy Also releases molecules and hormones that that affect appetite, blood pressure, immune system function, insulin and glucose levels Too much has negative health effects Visceral fat Found deep within the abdominal cavity Surrounds internal organs Subcutaneous fat Found just beneath the skin Insulates the body and regulates temperature

Basics of Body Composition My friends and I look about the same, but most of them weigh around 15 pounds less than I do. How is that possible? Differences in tissue density Differences between muscle and fat Differences in body composition

Figure 7-1 Body composition of young adults (ages 20–24)

Figure 7-2 Visceral and subcutaneous fat in the abdomen

Basics of Body Composition What is metabolism? Metabolism: all the processes that require energy (calories from foods) and maintain body functioning Energy balance: connection between metabolism and body composition

Basics of Body Composition The amount of energy your body requires depends on three criteria: Resting metabolic rate (RMR) Energy required to maintain essential processes at rest Depends on genetics, body size, and body composition Muscle is more metabolically active than fat Resistance training increases RMR Dietary thermogenesis The energy required to digest and process food Physical activity Energy expended in daily living as well as formal exercise

Basics of Body Composition How do we get fat, literally? What causes the body to retain fat, and where does it go? The body produces and stores fat when more energy is consumed than is used to maintain body functions and fuel activities Protects from starvation 3,500 calories is the equivalent of a pound of body weight More…

Basics of Body Composition Most fat is stored in fat deposits, which are about 80 percent fat and 20 percent support cells, immune cells, and blood vessels If you gain weight as fat, these fat cells enlarge, storing more fat If you lose body fat, your fat cells shrink

Basics of Body Composition Do overweight and obese mean the same thing? Obesity is considered more extreme and serious Overweight: weight above a recommended range, based on large-scale population surveys or studies Obesity: higher degree of overweight, characterized by excessive body fat Height and waist circumference are also considered in evaluating health risks

Basics of Body Composition Have Americans gotten fatter? On average, the American population has become heavier The average weight for adults in their twenties is 15 pounds heavier today than 20 years ago The prevalence of obesity has increased significantly

Figure 7-3 Trends in overweight and obesity among U. S Figure 7-3 Trends in overweight and obesity among U.S. adults, 1962–2010

Factors Affecting Body Composition Do shorter people have a higher body-fat percentage? Body composition is based on a combination of factors Height is related, but doesn’t predict the amount of body fat within your body Height is a body composition factor not in your control Some of the other factors, you can control

Genetics Is my body composition going to be similar to that of my parents? Is body composition based on genetics at all? The contribution of heredity will be between 25 and 75 percent Hundreds of genes affect body fat INSIG2 and FTO genes Influence body size; amount and distribution of body fat; and response to exercise Body composition is also influenced by numerous environmental factors

Genetics Why is it so hard for skinny guys to gain muscle mass? High resting metabolic rate Bodies that aren’t designed for muscle gain Can build muscle, but won’t be able to radically change body type

Biological Sex I know men and women’s bodies are different, but when my boyfriend and I eat together, it seems as if I am more susceptible to weight gain than he is. Why? Body composition differs between the sexes and varies with age Birth weights Young years Adolescence and puberty Mid-life

Figure 7-4 Average percent of body fat by age and sex

Biological Sex Why do men gain fat in their belly, and women in their hips? Men are more likely to store excess fat in the abdomen; women, in hips and thighs Android: apple-shaped; more common in men and postmenopausal women Gynoid: pear-shaped; more common in premenopausal women

Figure 7-5 Body-fat distribution

Age Does body composition always get worse as we get older? It is hard to separate the effects of age from use Less physical activity and exercise: With each decade they don’t strength train, adults lose about 4–6 pounds of muscle mass, and their resting metabolic rate also declines Physical activity and exercise, especially resistance training, can maintain muscle mass through the aging process

Ethnicity Do different ethnic groups have different body compositions? Body composition patterns related to sex and age are consistent across all ethnic groups However, ethnic differences have been found in average height, weight, and body composition Differences related to culture and ethnicity

Table 7-1 Comparison of Average Height, Weight, Body Mass Index, and Total Abdominal Fat Among Adults from Four Ethnic Groups

Lifestyle and Environment Some of my cousins are really fat, but my brothers and I are skinny. Why aren’t we more alike since we have many of the same genes? Genetics, age, and sex are factors in body composition, but different lifestyles and environments also play a role More…

Lifestyle and Environment Energy intake: if you consume more calories than you burn, you will gain weight Physical activity: daily activity and exercise affect energy balance and body composition Sleep: insufficient sleep is associated with increased body fat; may interfere with the ability to regulate appetite; and increases the risk of diabetes Stress: psychological stress linked to increased energy intake, weight gain, and excess abdominal fat; along with insulin resistance

Body Composition and Wellness Why is it important to know how much fat is in your body? What can one statistic like percent body fat tell you about health? Body composition is one component of health-related fitness Maintaining an appropriate level of body fat is vital to a healthy, longer life

Problems Associated with Excess Body Fat My dad is really big (I don’t like to say “fat”) and I worry about him. What are his greatest health risks? Cardiovascular disease High blood pressure and fat in the blood Type 2 diabetes There is a direct relationship between excess body fat and type 2 diabetes Cancer Breast, prostate, colon, pancreas, esophagus, endometrium, and kidney

Problems Associated with Excess Body Fat Other problems associated with excess body fat: Joint problems Osteoarthritis Sleep apnea Asthma Gall bladder and liver diseases Reproductive problems Shortened life expectancy

Problems Associated with Excess Body Fat Can you be sort of overweight or overfat and healthy at the same time? The consequences of excess body fat and weight are controversial and the subject of ongoing research Certain factors can make a difference Age and weight history An overweight youngster will be exposed to the effects of overweight for a longer period We usually gain fat and weight as we age More…

Problems Associated with Excess Body Fat Body-fat distribution Greater risk if excess is stored in abdomen rather than in hips and thighs Other health risk factors Additional risk factors: high blood pressure, elevated glucose Lifestyle Regular exercise can improve body composition and reduce risks associated with being overweight

Problems Associated with Too Little Body Fat What is the lowest body-fat percentage you can have and still maintain a healthy lifestyle? Is it even possible for a woman to have absolutely no body fat? It is not possible for anyone to have zero body fat A certain amount of body fat is essential for proper body function Consequences of low body fat, being underweight: Fluid imbalances, vitamin and mineral deficiencies, kidney problems Loss of bone mass, osteoporosis Reproductive disorders

Problems Associated with Too Little Body Fat If I exercise a lot and my period stops, is that a good thing or a bad thing? Female athlete triad Energy availability Low energy as a result of insufficient calorie intake or increased energy expenditure without increased calorie intake Menstruation Amenorrhea Bone health Reduced bone density

Figure 7-6 The female athlete triad

Body Composition and Athletic Performance I’m a runner. Will decreasing my body fat help make me faster? Many factors beyond body composition determine performance All being equal, a decreased level of body fat (that is still in the healthy range) might improve your performance and reduce your susceptibility to performance-related injuries Too little energy intake and body fat can harm both health and athletic performance There is no ideal percent body fat for each sport

Body Composition, Body Image, and Emotional Wellness What exactly is body image? Body image: a mental picture of your own body and how you feel about it Body dysmorphic disorder (BDD)—preoccupation with imagined defect in appearance Those with BDD generally have low self-esteem and may engage in compulsive behaviors More common in women Muscle dysmorphia—obsessed with the idea that one’s muscularity isn’t enough More common in men

Body Composition, Body Image, and Emotional Wellness Where does body image come from? The two key sources of body image (and self-esteem) are family and the media Family life Parents criticize the look of their children Friends and teachers also have an influence Media Fashion magazines TV shows and TV commercials Social networking

Figure 7-7 Average young women versus fashion models and Miss America (1920s–2000s)

Body Composition, Body Image, and Emotional Wellness So we’re supposed to worry about how we look for health reasons but not worry about how we look. How does that work? What’s important is what’s healthy Assess your body composition according to health criteria Avoid comparing yourself to unachievable ideals Instead, change the way you think about your body More…

Body Composition, Body Image, and Emotional Wellness Accepting your body: Focus on the positives Focus on health and healthy habits Realistically evaluate which aspects of your body you can change Set goals that are small and attainable Avoid negative self-talk about your body Recognize advertisements from the fitness and beauty industries as what they are Don’t judge the appearance of others

Assessing Body Composition What’s my ideal weight? It is hard to define an ideal weight It depends on other health risk factors Consider body composition Percent fat is a better indicator of health status than scale weight

Body Mass Index: An Indirect Measure How do I determine my BMI? Body mass index (BMI) One of most common techniques for assessing body fat Weight(kg) / Height2(m) BMI does not take into account muscle mass Waist circumference is used to classify health risks associated with different BMI values

Body Mass Index: An Indirect Measure Is BMI relevant and accurate for both athletes and people who are out of shape? BMI is only an indirect measure of body composition It is less accurate for athletes, those with above-average muscle mass, older adults, and certain ethnic groups

Figure 7-8 Body mass index

Table 7-2 Body Mass Index (BMI) Classification and Disease Risk

Methods for Estimating Percent Body Fat How can you determine body-fat percentages? Skinfold measurements Underwater (hydrostatic) weighing Bioelectrical impedance analysis (BIA) Air displacement plethysmography Dual X-ray absorptiometry

Table 7-3 Percent-Body-Fat Assessment Methods

Methods for Estimating Percent Body Fat What’s the right percent body fat for me? This depends on your age, sex, current body composition, and health status Goals are important too

Figure 7-9 Percent-body-fat standards for men and women

Methods for Assessing Body-Fat Distribution Does body shape make any difference when assessing weight and percent body fat? Body shape makes a difference Waist circumference Waist-to-hip ratio Waist-to-height ratio These provide some estimate of the risks associated with abdominal fat

Making Changes in Body Composition What’s a good goal for body weight and body fat? Set appropriate goals based on health assessments, health-risk factors Apply SMART criteria Seek medical advice if necessary Track progress toward goal

Making Changes in Body Composition What’s the best way to lose body fat? What’s the best kind of exercise to lose body fat? Focus on energy balance Look at both sides of the energy balance equation On the “energy out” side of the scale, body composition is best improved by a combination of exercise activities

Figure 7-10 Energy balance

Making Changes in Body Composition Why do I lose weight but not body fat? Weight loss does not automatically equal fat loss Dieting alone is not the best way to decrease body fat and improve body composition The best programs for fat loss include increased exercise and modest reductions in energy intake

Making Changes in Body Composition How much exercise do I need to maintain my weight range over time? To prevent weight gain: A minimum of 150 minutes per week of moderate-intensity aerobic exercise, or 75 minutes of vigorous-intensity exercise More…

Making Changes in Body Composition To lose a modest amount of weight or to maintain weight loss: More is better: 50 minutes a day of moderate-intensity exercise or 25 minutes of high-intensity exercise To lose significant amounts of weight: 300 minutes per week of moderate-intensity exercise or 150 minutes high-intensity exercise

Table 7-4 Approximate Calorie Costs of Selected Physical Activities

Making Changes in Body Composition Why can’t I just focus on improving one part of my body, such as getting rid of unwanted fat in one area? It is impossible to target one area for fat burning You can strengthen muscles in one area, but not reduce fat The exact area in which the body will mobilize fat for fuel depends on a number of factors, including genetics