Nutrition Chapter 9
Identify and explain the factors that affect basal metabolic rate.
AGE: The BMR is higher in youth; as lean body mass declines with age, the BMR slows. Physical activity may prevent some of this decline. HEIGHT: Tall people have a larger surface area, so their BMRs are higher. GROWTH: Children and pregnant women have higher BMRs. BODY COMPOSITION: The more lean tissue, the higher the BMR. A typical man has greater lean body mass than a typical woman, making his BMR higher. FEVER: Fever raises the BMR. STRESS: Stress hormones raise the BMR. ENVIRONMENTAL TEMPERATURE: Adjusting to either heat of cold raises the BMR. FASTING/STARVATION: Fasting/starvation hormones lower the BMR. MALNUTRITION: Malnutrition lowers the BMR. Thyroxine: The thyroid hormone thyroxine is a key BMR regulator; the more thyroxine produced, the higher the BMR.
List and define the three components of the body's energy expenditure (energy "out")
Basal Metabolism: The sum total of all the involuntary activities that are necessary to sustain life, including circulation, respiration, temperature maintenance, hormone secretion, nerve activity, and new tissue synthesis, but excluding digestion and voluntary activities. Basal Metabolism is the largest component of the average person's daily energy expenditure. Essentially, the total amount of energy needed to sustain life. Voluntary Activities: Intentional activities (such as walking, sitting, running) conducted by voluntary muscles. Basically, exercise. Thermic effect of food (TEF): The body's speeded-up metabolism in response to having eaten a meal; also called diet-induced thermogenesis. Basal Metabolic Rate (BMR): The rate at which the body uses energy to support its basal metabolism. Typically it goes like this: 25-50% Physical activity (voluntary activities) 50-65% BMR 5-10% Thermic effect of food
Body Composition
Body Composition: The proportions of muscle, bone, fat, and other tissue that make up a person's total body weight. -Controlling body composition is more important than controlling body weight.
Central Obesity (visceral fat). Amount of calories in 1 pound of fat.
Central Obesity: Excess fat in the abdomen and around the trunk. Visceral Fat: Fat stored within the abdominal cavity in association with the internal abdominal organs; als called intra-abdominal fat. Central Obesity facts: -Increases the risk of Type 2 Diabetes, storke, hypertension, and coronary artery disease. -May increase the risk of death. 1 pound of fat is equal to 3,500 calories.
Effects of fasting. Energy use during fasting. Why does metabolism slow down during fasting and very-low calorie diets?
Effects of fasting in order: -Less than 1 day into the fast: Liver glycogen stores are depleted. -Body cannot be converted to glucose in early food depravation. -Protein is broken down ad converted to glucose in order to meet the brain's need for glucose. Energy use during fasting goes like this: Storage component (Liver and muscle glycogen stores/body fat stores) is broken down in the body to either glucose (from liver and muscle glycogen stores) or fatty acids (from body fat stores) and then used for ENERGY. The metabolism slows down to conserve energy.
Female Athlete Triad
Female Athlete Triad: A potentially fatal triad of medical problems seen in female athlets: disordered eating, amenorrhea, and osteoporosis. Eating Disorder: -Restrictive dieting (inadequate energy and nurtrient intake) -Overexercising; -Weight loss; -Lack of body fat; Amenorrhea: -Diminished Hormones Osteoporosis: Loss of calcium from bones Eating Disorder / \ / \ \/ \/ Osteoporosis <-------------Amenorrhea
Appetite/hunger/satiety
Hunger: The physiological need to eat, experienced as a drive for obtaining food; an unpleasant sensation that demands relief. Occurs 4-6 after eating. Appetite: The psychological desire to eat; a learned motivation and a positive sensation that accompanies the sight, smell, or thought of appealing foods. Can be experienced without hunger. Satiety: The perception of fullness that lingers in the hours after a meal and inhibits eating until the next mealtime. Satiety generally determines the length of time between meals. Suppresses hunger.
Normal fat % for men and women.
Male: 12 and 20% Female: 20 and 30%
BMI used to define health/body weight/obesity. When should we NOT use BMI?
Using BMI has major drawbacks: It fails to indicate how much of a person's weight is fat, where the fat is located, and it does not measure body % fat vs % lean mass One should not use or rely on BMI with: -ATHLETES (because their highly developed musculature falsely increase their BMI values). -PREGNANT AND LACTATING WOMEN (because their increased weight is normal during child-bearing). -ADULTS OVER AGE 65 (because BMI values are based on data collected from younger people and because people "grow shorter" with age). -WOMEN OLDER THAN AGE 50 WITH TOO LITTLE MUSCLE TISSUE (they may be overly fat for health yet still fall into the normal BMI range)
Waist circumference
Waist Circumference: A measurement of abdominal girth that indicates visceral fatness Through waist circumference, Central Obesity is measured by placing a nonstretchable measuring tape around the waist just above the bony crest of the hip. The tape is snug but does not compress the skin..