Part I:(Hint: please use websites or ULR as references.)The obesity epidemic is expanding (no pun intended).Large sums of money are going to support the diet and fitness industry. Yet, all we have to do is look around to know thatthe prevalence of overweight, and risk factors such as Type 2 Diabetes are increasing by the minute. In Lectures 10 and 11 we learn the basics of energy balance, Calorie expenditure, metabolism, body composition, and the different exercise modalities. Choose one of the following to start your thread, and reply to two of your classmates who chose a different topic. Include personal experience if appropriate. As usual, include a credible reference to justify your response, andfeel free to post additional replies after your requirements are met.
- Does severely restricting any of the following lead to long term weight (fat) loss?(Pick only one.):
- The difference between simple weight loss and actual fat loss, Distinguish BMI frombody composition. Include the effect of body composition on BMR.
- The effect of strength training vs. cardio-respiratory training on body composition and BMR?
- Why are there few ectomorphs around, relative to endomorphs?
- Benefits of HIIT - an exercise technique that is not included in your lectures.
Part II(about 50 words is good enough):Write a short reply to the following post(I'll post it once you finish the part I)
PowerPoint Presentation Bio 125 Distance Learning Lecture 10 Janine Grant ENERGY BALANCE Learning Objectives: To understand the basics of Energy Balance: The amount of energy (Calories) from food consumed vs. the amount of energy expended Body Composition Assessing Regulating Weight Management Regulation of Food Intake 1 1 Definition of Energy: the ability to do work Energy that is stored in macronutrients (carbohydrate, fat and protein) and ethanol (alcohol) is converted via cellular respiration (Kreb’s aka Citric Acid cycle) into ATP – adenosine triphosphate, a high-energy compound. The Citric Acid Cycle uses oxygen and produces ATP, carbon dioxide and water. In the United States and Canada, we measure food energy in terms of kilocalories (kcalories, kcal, or Calories). The kilocalorie is the amount of energy required to raise the temperature of 1 kilogram of water 10 Celsius. 1000 calories = 1 kilocalorie, or food Calorie. Energy-yielding nutrients provide kilocalories. Energy in food = kilocalories The amount of energy consumed equals the amount of energy expended when the body is in energy balance. When energy balance is positive, excess is stored, mostly as fat. When energy balance is negative, stored energy will be used to fuel the body and weight will be lost. (at least in theory) 2 ENERGY IN FOOD Bomb calorimeter – measures the energy content of food. It consists of a chamber surrounded by a jacket of water. Food is dried, placed in the chamber and burned. The heat released raises the temperature of the water – and the increase in temperature is used to determine the kilocalories contained in the food. Since there are indigestible substances present in food, the bomb calorimeter value will be slightly higher than the actual value. ENERGY STORES IN THE BODY Energy is stored in the body primarily as triglyceride (fat). Some energy is stored as glycogen in the liver and muscles. - about 24 hours worth. Stored energy can be used between meals, during sleep, or over long-term food deprivation. We do not store amino acids. Nitrogen from excess protein intake will be excreted as urea and the carbon skeleton will be converted to fat or used for energy. See protein lecture 4. We do not store alcohol. It is toxic, therefore it is preferentially metabolized to yield ATP. 3 4 Building Energy Stores: After intake of food, nutrients are incorporated into the body as follows: – amino acids from dietary protein are used to synthesize body proteins and other molecules, carbohydrate is used to maintain blood glucose and to build glycogen stores, fat is used for energy or stored in the body. There is almost no limit to fat storage. Adipose tissue is made of adipocytes (fat cells). With the help of lipoprotein lipase, adipocytes store triglycerides that are picked up from the blood. The cells grow in size. It is thought that the number of adipocytes remain stable unless there is excessive weight gain. Excess carbohydrate and protein intake can be stored as fat. Using Energy Stores: The body must have a steady supply of energy with some of it coming from the metabolism of glucose. Between meals, the glucose comes from stored glycogen. (Remember, the brain and the red blood cells depend on glucose). The breakdown of stored fat meets other energy needs. Whatever is used is typically replaced at the next meal. When food is restricted over time, glycogen stores are expended, and the body must rely on the breakdown of body protein to yield amino acids, that are converted to glucose via gluconeogenesis. Energy for tissues that don’t require glucose can come from the breakdown of adipose tissue. When carbohydrate intake is restricted, the fatty acids cannot be completely oxidized and ketone bodies are produced. During prolonged food deprivation, the use of stored fat, and protein breakdown for gluconeogenesis leads to weight loss. 5 6 ENERGY OUTPUT (Total Energy Expenditure, or TEE) Basal Needs: About 60-75% of the body’s total energy requirement is needed for involuntary body functions such as breathing and circulating blood. The rate of energy expenditure for basal body functions is called Basal Metabolic Rate (BMR), also known as Basal Energy Expenditure (BEE). It is measured in the morning immediately after awakening after at least 12 hours with no food intake. It is more practical to measure energy needs after only 5-6 hours without food or exercise, called Resting Metabolic Rate (RMR). The RMR is estimated to be about 10-20% higher than BMR. The BMR/RMR does not take into account the energy required for physical movement and for digesting food. Factors that affect BMR/RMR: Body weight, lean body mass, gender, fever, thyroid hormone, low kilocalorie diets. Chronically low food intake will lower BMR. Physical Activity: The second major component of Total Energy Expenditure, physical activity typically accounts for 15 to 30% of energy requirements. This varies greatly because of individual differences in activity level, and because body size affects how much energy a particular action requires. Physical activity represents both structured exercise and the energy required for typical daily activities (Non-Exercise Activity Thermogenesis, or NEAT). Thermic Effect of Food: The Thermic Effect of Food (TEF) is the energy expended above BMR for the digestion, absorption, metabolism and storage of nutrients. The body temperature rises slightly after eating for several hours. TEF typically accounts for about 10% of energy intake and varies according to size of meal, and nutrient composition. For example, it is thought that protein metabolism uses the greatest amount of energy. 7 7 8 In summary: Energy output incorporates BMR, Physical Activity, and TEF ENERGY INTAKE REQUIREMENTS The kilocalorie intake needed to support energy output: BMR, Physical Activity, and TEF (same as energy output, or TEE). Plus energy needed during growth and pregnancy Plus a small amount of energy required to maintain body temperature in a cold environment. When an individual is in energy balance, Energy Output = Energy Intake 9 MEASURING ENERGY EXPENDITURE Direct Calorimetry - a measurement of heat production (Combusting food in a bomb calorimeter is one example). To measure energy expenditure in humans, a person is placed in an insulated chamber that measures the heat given off by the body. This is not often used because of the expense and inconvenience. Indirect Calorimetry - easier to administer, estimates energy use. This test measures energy needs by having the subject breathe into a ventilated hood. Food use for fuel in the body uses oxygen and produces carbon dioxide. Analyzing the difference between inhaled and exhaled air by measuring oxygen intake and carbon dioxide production can provide an estimate of fuel usage. In lab settings only (optional for you to know): Doubly Labeled Water Technique - The subject ingests or is injected with water labeled with isotopes of oxygen and hydrogen. These elements are used during metabolism and the rate of disappearance from the body can be measured. This measurement can be used to measure daily energy expenditure but not the proportion of energy used for BMR, physical activity, or TEF. 10 BODY WEIGHT (FAT) AND HEALTH Some body fat is essential to health. It cushions internal organs, provides an energy stores, and insulates against temperature changes. Health risks of being overweight by having too much body fat include hypertension, heart disease, stroke, elevated blood lipids, especially serum triglycerides, Type 2 Diabetes, gallstones, cancer, sleep disorders, respiratory problems, arthritis, hiatal hernia, pregnancy risks, immune system dysfunction. The rate of childhood obesity is skyrocketing and children are succumbing to health issues previously seen mainly in older people. Overweight children who become overweight adults have lifelong health risks. Being overweight has psychosocial ramifications for children, adolescents and adults. The distribution of body fat affects the degree of risk (see below). 11 EVALUATING BODY WEIGHT Body Mass Index (BMI) Method that relies on measures of weight in relation to height: BMI = weight in kg/(height in m)2 or, weight in lbs/(height in inches)2 X 703 Or find BMI calculator on internet and plug in your numbers. Healthy: 18.5 – 24.9 Overweight: 25 – 29.9 Obese: 30 or higher Morbid Obesity: 40 or higher BMI does not take into account body composition, therefore an individual might have, for example, a high BMI but not have excess body fat. 12 BODY COMPOSITION The proportion of weight that is lean tissue vs. fat. Women have a higher percentage of body fat than men, who have a higher percentage of muscle mass. Body composition: Relative amounts of lean mass vs. fat mass. Lean Mass: bones, connective tissue, muscle, body fluids Fat Mass: Subcutaneous (between muscles and skin). Intramuscular (stored within muscle). Visceral (surrounds organs) aka “belly fat”. “Belly fat” can also be subcutaneous. Approximate Range of Body Fat % for Healthy Young Adults Males – 8-19% Females – 21-32% Essential Body Fat: (not in text) The minimum amount of body fat required to maintain normal physiological functioning. Women need more than men to support childbearing. Essential body fat for adult males is approximately 5% of body weight, and for adult females is approximately 12% of body weight. 13 METHODS FOR ASSESSING BODY COMPOSITION: Bioelectrical Impedance Analysis A painless low-energy electrical current directed through the body. Fat is a poor conductor of electricity, the portion of the body that allows current to flow is considered lean tissue, the rest is assumed to be body fat. Hydration status affects the accuracy of this measurement Skinfold Thickness Subcutaneous fat is measured at different parts of the body and plugged into a mathematical equation. This test, if administered accurately, can provide accurate estimates of total body fat in normal weight individuals, less accurately in obese subjects. Underwater weighing An individual is weighed on dry land and under water. The difference between the two weights can be used to determine body volume. The values are plugged into a standardized equation to determine body fat. Considered a very accurate test when performed correctly. 14 BODY FAT DISTRIBUTION AND HEALTH Subcutaneous fat, or fat located under the skin, carries less of a health risk than visceral fat, or fat that is deposited around the organs. In general, fat deposited on hips and legs is subcutaneous, and fat deposited around the waist and abdomen is mostly visceral fat. However, abdominal fat can also be subcutaneous. Overweight people who are “apples” generally have more health risks (related to visceral fat) that overweight people who are “pears”.