Understanding Body Composition Chapter 7
Body Composition n Body composition is the ratio between fat and fat-free mass n Fat-free mass includes all tissues exclusive of fat (muscle, bone, organs, fluids) n Essential fat is necessary for normal biological function Essential fat for men is 3% to 5% of total weight; it is 8% to 12% percent for women
Obesity and Overweight n Obesity is overfatness Obesity in men is defined as body fat equal to or greater than 25% of total body weight Obesity in women is defined as body fat equal to or greater than 35% of total body weight n Overweight is excessive weight for height and does not consider body composition
Regional Fat Distribution n Most women store fat in the hips, buttocks, thighs, and breasts (gynoid fat) n Most men store fat in the abdomen, lower back, chest, and nape of the neck (android fat) n Intra-abdominal fat is stored deep in the abdominal cavity and carries a high risk for certain diseases
Regional Fat Distribution n The android pattern of deep fat deposition is related to an increase risk for heart disease, stroke, diabetes, and some form of cancer Enzymes in abdominal fat cells allow these fat cells to be routed directly to the liver for the production of cholesterol Abdominal cells are larger than other fat cells; large fat cells are associated with blood glucose intolerance and excessive blood insulin (associated with diabetes) Excessive blood insulin may interfere with the removal of sodium by the kidneys and promote hypertension
Methods of Measuring Body-Weight Status n Waist-to-hip ratio (WHR) is a simple method for determining the disruption of body fat n Height/weight tables do not reflect body composition and are poor instruments for weight-loss recommendations n Body mass index (BMI) is the ratio of body weight in kilograms to height in meters squared People with BMIs of 25 to 29.9 are considered overweight; people with BMIs of 30 or higher are considered obese
Measuring Body Composition n The only direct way to measure the fat content of humans is through chemical analysis of cadavers n Underwater weighing is one of the most accurate indirect measurement techniques People with more muscle mass weigh more in water than those with less
Measuring Body Composition n Bioelectrical impedance analysis uses a low-level, single-frequency electric current to measure body composition n Skinfold measurements one of the most economical ways to measure body composition and, when performed by skilled technicians, correlate well with hydrostatic weighing n Air-Displacement Plethysmography Uses air displacement rather than water displacement for assessing body composition by sitting in the Bod Pod n Dual-Energy X-Ray Absorptiometry (DEXA) bone mineral density, quantification of fat, and lean tissue using very low exposures to radiation.
Understanding Body Composition Chapter 7
Achieving a Healthy Weight and Body Composition Chapter 8
Achieving a Healthy Weight n At any given time, more than one-half of women and one-fourth of men are on a diet n For some people the weight obsession can lead to serious body-image problems, including body dysmorphic disorder (BDD)
Obesity Trends Among U.S. Adults
Healthy Aspects of Obesity n Coronary heart disease n Stroke n Hypertension n LDL cholesterol n Diabetes n Psychological distress n Gallbladder disease n Osteoarthritis n Sleep apnea n Some cancers
Development of Obesity n Obesity occurs when the 30 to 40 million adipose (fat) cells in the body increase in size (hypertrophy), number (hyperplasia), or both n Gender differences in fat storage Males- upper half of body (android) Females- lower half of body (gynoid) n Biological factors that influence obesity are age, metabolism, gender, disease, and heredity
Adipose Cell Deposits
Development of Obesity n Heredity influences both body weight and body shape Ectomorph- long, thin body frames - slinder Endomorph- rounded physical features and large frames. Greatest capacity for fat storage. Mesomorph- muscular, athletic body frames n The set point theory suggests that the body works to maintain a certain weight no matter what a person does
Overeating n Overeating is consuming more calories than are required by the body n Most experts view high dietary fat intake as the major factor in obesity n Calories from fat appear to convert to body fat more readily than calories from carbohydrates and protein n Portion size
Inactivity n Some experts view lack of physical activity as the distinguishing factor that separates the obese from those of normal weight n Exercise alone is not a major component in weight loss, but it is the most important component in weight gain
Obesity: Contributing Factors n Overeating & physical inactive n Limited time n Family and social influences n Economic conditions n Workplaces n Communities n Psychology
Strategies for Weight Management or Weight Loss 1. Balance between caloric intake and caloric expenditure The loss of one pound of body fat requires a deficit of 3500 calories A desirable long-term goal for losing weight is 1 to 2 pounds a week until 10% of total body weight is lost A six-month maintenance program should follow weight loss before losing more
Strategies for Weight Management or Weight Loss 2. Dieting Only 5% of dieters successfully lose and maintain their weight loss for one year Weight cycling (yo-yo dieting) usually results in a greater weight gain following a loss period and increases the risk of death Caloric intake should not drop below 1200 per day for women or 1500 per day for men
Strategies for Weight Management or Weight Loss 3. Diet drugs Offer only a temporary solution and side effects can be deadly 4. Surgery 5. Herbal remedies and diet supplements 6. Fasting Can be harmful especially if done for a prolonged period of time 7. Physical activity The optimal approach to weight loss combines mild caloric restriction with regular physical activity
Physical Activity n Basal metabolic rate (BMR) is the energy required to sustain life when the body is rested and fasting n Persons who are deconditioned need to start slowly and progress gradually n Increased muscle tissue raises BMR n People who lose weight and keep it off almost always exercise daily n Low intensity exercise burns more fat calories
Eating Disorders n Anorexia nervosa the refusal to maintain minimally normal weight for age and height. characterized by the refusal to eat n Bulimia nervosa alternates bingeing with purging (Symptoms of disordered eating are also serious n Binge-eating disorder consuming large amounts of food in one sitting lack of control n Female athlete triad is common among young athletes disordered eating, amenorrhea, osteoporosis
Principles of Weight Management n Avoiding an obsession with body weight n Avoiding fad diets n Avoiding fasting and restrictive dieting n Balance caloric intake and caloric expenditure n Developing a plan n Being physically active n Making gradual lifestyle changes
Achieving a Health Weight and Body Composition Chapter 8