(F/W)Chapter 6-Body Composition-Guide Questions
State the prevalence of overweight and obesity among Americans, and list at least three factors that have contributed to recent increases in the prevalence.
Americans are getting fatter. The prevalence of obesity has increased from about 13% in 1960 to about 34% today, and about 67% of adult Americans are now overweight. About 33% of adult men and 35% of adult women are obese. More time spent in sedentary work and leisure activities. Fewer trips on foot and more by automobile. Fewer daily gym classes for students.
Describe the health effects of too much and too little body fat.
Essential fat is necessary for the functioning of the body fat -- less than 8-12% for women and 3-5% for men -- as a threat to health. Extreme leanness is linked with reproductive, respiratory, circulatory, and immune system disorders and with premature death. Extremely lean people may experience muscle wasting and fatigue. They are also more likely to have eating disorders.
Explain the components of the female athlete triad and the health effects associated with the triad.
While obesity is at epidemic levels in the United States, many girls and women strive for unrealistic thinness in response to pressure from peers and a society obsessed with appearance. This quest for thinness has led to an increasingly common, underreported condition called the female athlete triad. The triad consist of three interrelated disorders: abnormal eating patterns (and excessive exercising), followed by lack of menstrual periods (amenorrhea), followed by decreased bone density (premature osteoporosis). Left untreated, the triad can lead to decreased physical performance, increased incidence of bone fractures, disturbances of heart rhythm and metabolism, and even death.
Define body mass index, and explain how it is calculated. List the NIH and WHO classifications and cutoffs for BMI.
Body mass index (BMI): (measure of body weight that is useful for classifying the health risks of body weight if you don't have access to more sophisticated methods.) a 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). National Institutes of Health (NIH) and the World Health Organization (WHO), a BMI between 18.5 and 24.9 is considered healthy. A person with a BMI of 25 or above is classified as overweight, and someone with a BMI of 30 or above is classified as obese. A person with a BMI below 18.5 is classified as underweight, although low BMI values may be healthy in some cases if they are not the result of smoking, an eating disorder, or an underlying disease. A BMI of 17.5 or less sometimes used as a diagnostic criterion for the eating disorder anorexia nervosa.
Describe the steps an individual should take if they are significantly overweight and/or have known risk factors for disease.
Consult your physician to determine a body composition goal for your individual risk profile. For people who are obese, small losses of body weight over a 6-12 month period can result in significant health improvements.
Describe body composition, including the concepts of essential fat, overweight, and obesity.
The human body can be divided into fat-free mass and body fat. Fat-free mass is composed of all the body's nonfat tissues. A certain amount of body fat is necessary for the body to function. Fat is incorporated into the nerves, brain, heart, lungs, liver, mammary glands, and other body organs and tissues. It is the main source of stored energy in the body; it also cushions body organs and helps regulate body temperature. This essential fat makes up about 3-5% of total body weight in men and about 8-12% in women. The primary source of excess body fat is excess calories consumed in the diet. A pound of fat is equal to 3500 calories, so an intake of just 100 calories a day in excess of calories expended will result in a 10-pound weight gain over the course of a years. When looking at body composition, the most important consideration is the proportion of the body's total weight that is fat -- the percent body fat. Overweight: body weight above the recommended range for good health; sometimes defined as a body mass index between 25 and 29.9. 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.
Define type 1 diabetes, type 2 diabetes, pre-diabetes, and gestational diabetes. List three risk factors and three preventive strategies for type 2 diabetes.
Type 1 Diabetes: the pancreas produces little to no insulin, so daily doses of insulin are required, and people with this may require other medications to control their blood sugar levels and other complications with this disease. (Without insulin, a person with this can lapse into a coma.) Usually strikes before age 30. (About 5-10% of people with diabetes have the more serious form.) Type 2 Diabetes: (The remaining 90-95% of people with diabetes have type 2. This condition can develop slowly, and about 25% of affected individuals are unaware of their condition.) The pancreas doesn't produce enough insulin, cells are resistant to insulin, or both. This condition is usually diagnosed in people over age 40, although there has been a tenfold increase in type 2 in children in the past two decades. About one-third of people with type 2 must take insulin; other medications that increase insulin production or stimulate cells to take up glucose. Pre-diabetes: blood glucose levels that are higher than normal but are not high enough for a diagnosis of full-blown diabetes. (According to 2010 estimates from the American Diabetes Association, about 79 million Americans have pre-diabetes; experts warn that most people with the condition will develop type 2 diabetes unless they adopt preventive lifestyle measures. Gestational Diabetes: (Occurs in 2-10% of women during pregnancy.) Usually disappears after pregnancy, but 5-10% of women go on to have type 2 diabetes immediately after pregnancy. (Women who had gestational diabetes during pregnancy have up to a 60% chance of developing diabetes in the next 10-20 years.
List and describe three techniques for estimating percent body fat.
Underwater Weighing: in hydrostatic (underwater) weighing, an individual is submerged and weighted under water. The percentages of fat and fat-free weight are calculated from body density. (More body fat--tend to float and weigh less, and lean people tend to sink and weigh more.) The Bod Pod: a small chamber containing computerized sensors, measures body composition by air displacement. (Technique's technical name is plethysmography.) It determines the percentage of fat by calculating body density from how much air is displaced by the person sitting inside the chamber. Skinfold Measurements: skinfold measurement is a simple, inexpensive, and practical way to assess body composition. Skinfold measurements can be used to assess body composition because equations can link the thickness of skinfolds at various sites to percent body fat calculations from more precise laboratory techniques.