Energy Balance and Body Composition
Factors that Influence Energy Expenditure
1) Gender: women generally have a lower BMR than men, in large part because men typically have more lean body mass. 2) Growth: people who are growing have a higher BMR. 3) Age: BMR declines during adulthood as lean body mass diminishes (physical activity, appetite, body weight, metabolism). 4) Physical activity: energy equations include a physical activity factor for various levels of intensity for each gender. 5) Body composition and body size: height and weight are both considered in energy equations. 6) Genetic differences.
Physiological Fuel Value
A bomb calorimeter measures the available energy in foods but overstates the physiological fuel value-the amount of energy that the human body derives from foods.
Stress Fractures
A stress fracture is caused by bone damage or breaks caused by stress on bone surfaces during exercise.
Adaptive Thermogenesis
Adaptive thermogenesis are adjustments in energy expenditure related to changes in environment such as extreme cold and to physiological events such as overfeeding, trauma and changes in hormone status. *not included when calculating energy requirements
Amenorrhea
Amenorrhea is the absence of or cessation of menstruation. Amenorrhea is characterized by low blood estrogen, infertility, and often bone mineral losses. Excessive training, depleted body fat, low body weight, and inadequate nutrition all contribute to amenorrhea.
Anorexia Nervosa
Anorexia nervosa is an eating disorder characterized by a refusal to maintain a minimally normal body weight and a distortion in perception of body shape and weight. Characteristics: distorted body image, need for self-control, trauma, malnourishment, growth ceases, normal development falters, loss of lean tissue, BMR slows, the heart pumps inefficiently and irregularly, blood pressure falls, loss of brain tissue, impaired immune response, anemia, loss of digestive functions, loss of sex drive, amenorrhea Treatment: multidisciplinary approach, stop weight loss while establishing regular eating patterns, clients are classified based on indicators of malnutrition, denial runs high, families are involved, professional assessment
Appetite
Appetite prompts a person to eat-or not to eat. Somehow the body decides how much and how often to eat-when to start eating and when to stop. Many signals initiate or delay eating.
Basal Metabolism
Basal metabolism is the energy needed to maintain life when a body is at complete digestive, physical and emotional rest. About two-thirds of the energy the average person expends in a day supports the body's basal metabolism.
Some People Need More Body Fat
Below a certain threshold for body fat, hormone synthesis falters and individuals may become infertile, develop depression, experience abnormal hunger regulation or become unable to keep warm.
Binge-Eating Disorder
Binge-eating disorder is an eating disorder with criteria similar to those of bulimia nervosa, excluding purging or other compensatory behaviors. People consume less during a binge, rarely purge, and exert less restraint during times of dieting. People feel out of control, disgusted, depressed, embarrassed, guilty, or distressed.
Body Composition
Body composition is the proportions of muscle, bone, fat and other tissue that make up a person's total body weight. Body Weight = Fat + Lean Tissue (Including Water)
Associated Health Risks
Body weight and body fat correlate with disease risks and life expectancy. The correlation suggests a greater likelihood of developing a chronic disease and shortening life expectancy for those with a higher BMI. Correlations are not causes. Epidemiological data show a J or U shape relationship between body weights and mortality.
Energy Imbalance
Both excessive and deficient body fat result from an energy imbalance.
Bulimia Nervosa
Bulimia nervosa is an eating disorder characterized by repeated episodes of binge eating, usually followed by self-induced vomiting, misuse of laxatives or diuretics, fasting or excessive exercise. Characteristics: typically single, female and white, may interfere with work, anxiety, cannot easily establish relationships, depression, impulsive, low self-esteem, body image and food, no control over eating, swollen hands and feet, bloating, fatigue, headaches, nausea, and pain after a binge, clinical depression, substance abuse Consequences: malnutrition, fluid and mineral imbalances, abnormal heart rhythms, injury to the kidneys, irritation and infection of the pharynx, esophagus, and salivary glands, erosion of the teeth, and dental carries, esophagus and stomach may rupture, calloused hands, red eyes Treatment: weight maintenance, cognitive behavioral therapy, mental health professionals are involved
Energy Values (Review)
Carbohydrate=4 Fat=9 Protein=4 Alcohol=4
Central Obesity
Central obesity refers to excess fat around the trunk of the body.
Health Risks of Overweight
Diabetes, hypertension, cardiovascular disease, sleep apnea, osteoarthritis, some cancers, gall bladder disease, kidney stones, respiratory problems, infertility and complications in pregnancy and surgery are all side effects of obesity. Obesity-related illness costs our nation $147 billion-in fact, as much as, or more than, the medical costs of smoking. Mortality increases as weight increases.
Disordered Eating
Disordered eating refers to eating behaviors that are neither normal nor healthy, including restrained eating, fasting, binge eating and purging.
Gastrointestinal Hormones
Dozens of gastrointestinal hormones influence appetite control and energy balance.
Satiation
During the course of a meal, as food enters the GI tract and hunger diminishes, satiation occurs. As receptors in the stomach stretch and hormones such as cholecystokinin become active, a person begins to feel full. The response: satiation, which prompts a person to stop eating.
Weight Loss
Fluctuations in body weight may also increase the risks of chronic diseases and premature death. In contrast, sustained weight loss improves physical well-being, reduces disease risks, and increases life expectancy.
"Energy In"
Foods and beverages provide the "energy in" part of the energy-balance equation.
Some People Need Less Body Fat
For many athletes, a lower percentage of body fat may be ideal-just enough to provide fuel, insulate and protect the body, assist in nerve impulse transmissions and support normal hormone activity but not so much as to burden the body with excess bulk.
Osteoporosis
For most people, weight-bearing physical activity, dietary calcium and (for women) the hormone estrogen protect against the bone loss of osteoporosis. For young women with disordered eating and amenorrhea, strenuous activity can increase bone turnover and impair bone health,
Eating Disorders
For some people, the struggle with body weight manifests itself as an eating disorder. Three eating disorders-anorexia nervosa, bulimia nervosa and binge eating disorder-are relatively uncommon but present real concerns because of their health consequences. Most experts agree that eating disorders are caused by sociocultural, physiological and perhaps neurochemical factors.
Other Measures of Body Composition
Health-care professionals commonly use BMI and waist circumference measurements because they are relatively easy and inexpensive. Researchers sometimes estimate body composition using total body water, radioactive potassium count, near-infrared spectrophotometry, ultrasound, computed tomography, and magnetic resource imaging. Each method has advantages and disadvantages with respect to cot, technical difficulty and precision of estimating body fat.
General Rules
In general, the more a person weighs, the more total energy is expended on basal metabolism, but the amount of energy per pound of body weight may be lower. For the most part, the BMR is highest in people who are growing and those with considerable lean body mass. The BMR slows down with a loss of lean body mass and during fasting and malnutrition.
Inflammation
Inflammation is an immunological response to cellular injury characterized by an increase in white blood cells. Inflammation contributes to chronic diseases. Fat accumulation, especially in the abdominal region, activates genes that code for proteins (adipokines) involved in inflammation. Furthermore, although relatively few immune cells are commonly found in adipose tissue, weight gain significantly increases their number and their role in inflammation. Elevated blood lipids-whether due to obesity or to a high-fat diet-also promotes inflammation. Together, these factors help to explain why chronic inflammation accompanies obesity and how obesity contributes to the metabolic syndrome and the progression of chronic diseases.
Insulin Resistance
Insulin resistance is the condition in which a normal amount of insulin produces a subnormal effect in muscle, adipose and liver cells, resulting in an elevated fasting glucose; a metabolic consequence of obesity that precedes type 2 diabetes.
Lean Body Mass
Lean body mass is the body minus its fat.
Type 2 Diabetes
Most adults with type 2 diabetes are overweight or obese. Furthermore, the person with type 2 diabetes often has central obesity. Central body fat cells appear to be larger and more insulin-resistant than lower-body fat cells. Diabetes appears to be influenced by weight gains as well as by body weight.
Muscle Dysmorphia
Muscle dysmorphia is a psychiatric disorder characterized by a preoccupation with building body mass. Other athletes may restrict fluid and food intake to "make weight."
Neuropeptide Y
Neuropeptide Y causes carbohydrate cravings, initiates eating, decreases energy expenditure and increases fat storage-all factors favoring a positive energy balance and weight gain.
Obese
Obese refers to too much body fat with adverse health effects; BMI 30 or more.
Overweight
Overweight refers to a body weight greater than the weight range that is considered healthy; BMI 25-29.9.
Hunger
People eat for a variety of reasons, most obviously (although not necessarily most commonly) because they are hungry. Most people recognize hunger as an irritating feeling that prompts thoughts of food and motivates them to start eating. In the body, hunger is the physiological response to a need for food triggered by nerve signals and chemical messengers originating and acting in the brain, primarily in the hypothalamus.
Body Weight
People often mistakingly turn to friends and fashion for the ideal body weight. In terms of health, ideally, a person has enough fat to meet basic needs, but not so much as to incur health risks.
Physical Activity
Physical activity is the most viable-and the most changeable-componenet of energy expenditure. Consequently, its influence on both weight gain and weight loss can be significant. The amount of energy needed for any activity, whether playing tennis or studying for an exam depends on three facts: muscle mass, body weight, and activity. The larger the muscle mass and the heavier the weight of the body, the more energy is expended.
Satiety
Satiety is the feeling of fullness and satisfaction that occurs after a meal and inhibits eating until the next meal. Satiety determines how much time passes between meals.
Overriding Hunger and Satiety
Some people experience food cravings when they are bored or anxious. Some people may eat in response to any kind of stress, positive or negative. Repeatedly eating to relieve chronic stress can lead to overeating and weight gain. Many people respond to external cues such as the time of day or the availability, sight and taste of the food (environmental cues). Cognitive influences-such as perceptions, memories, intellect, and social interactions can easily lead to weight gain. Eating can also be suppressed by signals other than satiety, even when a person is hungry.
Health Risks of Underweight
Some underweight people enjoy an active, healthy life but others are underweight because of malnutrition, smoking habits, substance abuse or illness. An underweight person, especially an older adult, may be unable to preserve lean tissue during the fight against a wasting disease such as cancer or a digestive order, especially when the disease is accompanied by malnutrition. Underweight women develop menstrual irregularities and become infertile. Osteoporosis is also associated.
Subcutaneous Fat
Subcutaneous fat is fat around the hips and thighs, sometimes referred to as lower-body fat and is most common in women during their reproductive years.
Metabolic Syndrome
The accumulation of fat, especially in the abdominal region changes the body's metabolism, resulting in insulin resistance, low HDL, high triglycerides and high blood pressure. This cluster of symptoms-collectively known as the metabolic syndrome-increases the risks for diabetes, hypertension and atherosclerosis.
Energy Balance
The amount of body fat a person deposits in, or withdraws from, storage on any given day depends on the energy balance for that day-the amount consumed (energy in) versus the amount expended (energy out).
Basal Metabolic Rate
The basal metabolic rate (BMR) is the rate of energy used for metabolism under specified conditions: after a 12-hour fast and restful sleep, without any physical activity or emotional excitement, and in a comfortable setting. It is usually expressed as kilocalories per kilogram body weight per hour.
Body Mass Index
The body mass index describes relative weight for height. BMI reflects height and weight measures and not body composition. BMI = weight (kg)/height (m2) OR [weight (lb)/height (in)^2] X 703
Sustaining Satiation and Satiety
The extent to which foods produce satiation and sustain satiety depend in part on the nutrient composition of a meal. Of the three energy-yielding nutrients, protein is considered the most satiating. Foods with a high energy density provide more kilocalories and those with low energy density provide fewer kilocalories, for the same amount of food. Foods low in energy density are also more satiating. Although fat provides little satiation during a meal, it produces strong satiety signals once it enters the intestine. Fat in the intestine triggers the release of cholecystokinin-a hormone that signals satiety and inhibits food intake.
Female Athlete Triad
The female athlete triad is a potentially fatal combination of three medical problems-disordered eating, amenorrhea and osteoporosis.
The Hypothalamus
The hypothalamus appears to be the control center, integrating messages about energy intake, expenditure and storage from other parts of the brain and from the mouth, GI tract and liver. Some of these messages influence satiation, which helps control the size of a meal; others influence satiety, which helps determine the frequency of meals.
Fat Distribution
The location of fat on the body may influence health as much, or more than, total fat alone.
Cardiovascular Disease
The relationship between obesity and cardiovascular disease risk is strong, with links to both elevated blood cholesterol and hypertension. Lean and normal-weight people may also have high blood cholesterol and blood pressure.
Resting Metabolic Rate
The resting metabolic rate is similar to the basal metabolic rate, a measure of energy use for a person at rest in a comfortable setting, but with a less stringent criteria for recent food intake and physical activity. Consequently, the RMR is slightly higher than the BMR.
Cancer
The risk of some cancers increases with both body weight and weight gain, but researchers do not fully understand their relationships. One possible explanation may be tat obese people have elevated levels of hormones that could influence cancer development.
Thermic Effect of Food
The thermic effect of food is an estimation of the energy required to process food (digest, absorb, transport, metabolize, and store ingested nutrients). The sum of the TEF and any increase in the metabolic rate due to overeating is known as diet-induced thermogenesis. The thermic effect of food is proportional to the food energy taken in and is usually estimated at 10% of energy intake. Carbohydrate: 5-10% Fat: 0-5% Protein: 20-30% Alcohol: 15-20% *usually ignored when estimating energy expenditure because its contribution to total energy output is smaller than the probable errors involved in estimating overall energy intake and output
Thermogenesis
Thermogenesis is the generation of heat and can be measured to determine the amount of energy expended. The total energy a body expends reflects the energy expended for basal metabolism, the energy expended for physical activity, the energy expended for food consumption, and the energy expended for adaptation.
Bomb Calorimeter
To find out how many kilocalories a food provides, a scientist can burn the food in a bomb calorimeter. When the food burns, energy is released in the form of heat. The amount of heat given off provides a direct measure of the food's energy value. These reactions also generate carbon dioxide and water (similar to the body's cells). The amount of oxygen consumed gives an indirect measure of the amount of energy released.
Cathartic
To purge food from the body, a cathartic may be used which is a strong laxative that can injure the lower intestinal track.
Emetic
To purge food from the body, an emetic may be used which is a drug intended as first aid for poisoning.
Underweight
Underweight refers to a body weight lower than the weight range that is considered healthy; BMI less than 18.5.
Unspecified Eating Disorders
Unspecified eating disorders are disorders that do not meet the defined criteria for specific eating disorders.
Visceral Fat
Visceral fat is fat stored within the abdominal cavity in association with the internal abdominal organs. Visceral fat is more common in males.
Waist Circumference
Waist circumference is an anthropometric measurement used to assess a person's abdominal fat. As waist circumference increases, disease risks increase. Waist circumference alone is the preferred method for assessing abdominal fat in a clinical setting.
Changes in Body Weight
When a person is maintaining weight, energy in equals energy out. When the balance shifts, weight changes. Weight gained or lost rapidly includes some fat, large amounts of fluid, and some lean tissues such as muscle proteins and bone minerals.
