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Chapter 10

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Simon Fraser University
Biomedical Physio & Kines
BPK 143
Tony Leyland

WEIGHT LOSS AS THE “HOLY GRAIL” OF THE FITNESS INDUSTRY - The ideal physique is different for each individual - Losing weight is non-specific and is not a SMART goal - Accurately measuring whether you have achieved goals is very difficult and expensive Strength, muscle, fat, and body composition - Develop strength by improving neuromuscular efficiency and increasing muscle size - Many women mistakenly feel that strength training will cause them to bulk up and look unattractive - Women, in general, do not bulk up - Loss of muscle mass has occurred with the diet-only approach - Health includes being able to function independently later in life - Dieting and losing muscle mass is not a good strategy to keep you independent as you age - Resistance weight training combined with endurance training improves fat loss - Adding resistance training in addition to diet and endurance training works on two levels, and resistance training maintains or improves muscle mass due to overload - If you lose body fat and gain muscle, you will “trim down” even if your weight remains constant - Muscle is about 18% denser than fat WEIGHT MANAGEMENT - There is an underlying pathology, individuals who eat correctly, exercise correctly, and manage their stress levels appropriately will maintain a body composition that is healthy for them - For the vast majority of people who are over-fat, it is lack of regular exercise and poor diet choices that are of concern - Not because of a high volume of food but it is often poor choice of foods, and in particular, large amounts of sugar, refined carbohydrates, and other high-glycemic foods ( foods that cause a rapid rise in blood glucose) - Eating fat does not make you fat - High-glycemic food cause a rapid rise in blood sugar and similar fast rise in blood insulin levels - Insulin is an essential hormone, but if levels are chronically elevated, the body will tend to store more fat and cells may become desensitized to insulin, eventually leading to type 2 diabetes - Many individuals eat wisely and exercise regularly but remain over-fat because of their genetic predisposition to have that type of body - Performance measures are better indicators of health and fitness Dietary Fat and Body Fat - Nutrition research has been conducted very poorly because of bias - Insulin: a hormone that regulates carbohydrates and fat metabolism. When you secrete insulin it signals cells in the liver, muscle, and adipose (fat) tissue to take up sugar from the blood. In the liver and muscle glucose is stored as glycogen and in adipose tissue it is converted to fat - Glycemic index (GI): a measure of the effects of foods on blood sugar levels. Carbohydrates with a GI rating can be digested quickly causing a rapid rise in blood sugar levels. Carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, have a low GI. Often this rapid rise in blood sugar results in a rise in insulin levels THE ENERGY BALANCE EQUATION - Energy balance equation (EBE) - Change in energy stores = energy intake – energy expenditure - Most weight loss programs have simply and wrongly treated energy intake and energy expenditure as two independent variables - Individuals who want to lose weight need to focus on decreasing caloric intake, increasing energy expenditure, or a combination of the two Energy intake - The food we eat elicits hormonal responses, which determine how energy is stored in the body- that is, in the form of body fat - Energy intake is NOT independent of energy expenditure, and the type of calories you eat does affect your energy output - Energy intake and energy expenditure are DEPENDENT variables - The storage and release of fat from adipose tissue (fat cells) is hormonally driven - The hormonal response to pregnancy stimulates fat accumulation in order to build ample energy supplies for both mother and fetus - The fat is usually stored in the buttocks, thighs, and breasts, and will be mobilized ) moved out of the cells) when energy is needed during pregnancy and lactation - After giving birth, a mother will return to a normal amount of adipose tissue for her, regardless of whether she eats more or fewer calories - It is poor eating habits that cause a hormonal response, which then forces the body to store excess calories as fat - Poor food intake includes high-carbohydrate calories, particularly simple sugars and refined flours, as well as total carbohydrate intake - Restricting total carbohydrates, along with eating only carbohydrates that are low on the GI, is the most effective diet for weight control and good health - Hormones stimulate appetite and dictate how this “excess” of nutrients is stored - For children, the growth will include muscle, bone, and organ growth as well as some adipose tissue - For an adult, the hormonal response will cause growth in the form of fat accumulation - Individuals on low-calories weight-loss diet tolerate high-fat, high-protein, low-carbohydrate diets better than low-fat diets - Despite low overall calorie intake, they do not report feeling hungry all the time, and their metabolism does not slow down in an attempt to maintain fat stores - All calories are not equal; the quality of those calories ( the type of nutrient and overall nutrient balance) is very important - Restricting calories intake but continuing to eat much of it in the form of high-glycemic foods will make the body fight to maintain its fat stores and will lower the metabolism - Your body secretes the hormone, insulin, in response to a rise in blood sugar. - Insulin drives the body to store the excess blood sugar as fat. Remember I showed in Chapter 6 that we do not store a lot of energy in the form of glycogen. - Insulin inhibits your body’s ability to mobilize fat out of adipose tissue and burn it as a fuel. Therefore, high insulin levels work against fat loss. - Simple carbohydrates (e.g., high-fructose corn syrup, sugar, and white flour) increase blood sugar levels the most, and increase insulin levels. - Very high total-carbohydrate quantities in diets also increase insulin levels. - Chronically elevated levels of insulin are responsible for metabolic syndrome, which includes obesity, Type 2 diabetes, high blood pressure, and more ENERGY OUT - Understanding the relationship between exercise and weight control lies in understanding the body’s hormonal response to exercise - Steady-state low-power activities are less than ideal for improving aerobic conditioning and ineffective at stimulating significant production of testosterone, human growth hormone, and the other hormones involved in optimal health and body composition - A calories burned is a calorie burned is too simplistic - The type of calories are you eating and the type of exercise you are doing make a difference - High power outputs elicit different hormonal response than low-power steady-state ones - Individuals experience a greater amount of fat breakdown, or lipolysis, from performing two 30-minute sessions than one 60-minute session - The repeated trial caused a greater increase in free fatty acids and glycerol, which are released when stored fat is burned - Levels of epinephrine increased while levels of insulin and blood glucose decreased significantly more than during the single session, which may have further contributed to fat breakdown - Repeated bouts of exercise cause enhanced fat metabolism compared with a single bout of prolonged exercise of equivalent total exercise duration - If you are doing the same amount of work in two comparable but different exercises and yet find one type of exercise more fatiguing, and if you do the same amount of work and yet lose more subcutaneous body fat with one type of exercise, then something else is going on other than a simple calculation of calories expended - Hormonal response to exercise is vitally important - Hormonal response to high-power activities includes increased levels of tesoterone, insulin-like growth factor, human growth hormone, and many others - Intense work causes more cellular damage - On the cellular level, exercise is a stressor- a debilitating process that forces the body to rebuild tissue and strengthen- and there are important hormones involved in this rebuilding process - The metabolism stays elevated for much longer after a high power activity, due to the action of adrenal gland hormones, as compared with low power workout - Quantity of calories eaten is still relevant - High intensity levels, across all metabolic pathways, using large percentage of body musculature, are key factors in the efficacy of high intensity activities, like anaerobic sports and resistance training programs, with respect to body composition and weight control - The adaptation and hormonal response to performing only long, slow, low-powereted aerobic work is less effective in driving a healthy hormonal response and a truly healthy body composition- that is, one that includes adequate musculature in all regions of the body, good bone and connective tissue density and healthy body fat levels - As an individual’s fitness increases, adding resistance work and then high-intensity interval work will help normalize gene expression and hormonal balance - The quality of the exercise performed is as important as the quantity of calories expended FAT CELL SIZE AND NUMBER - The body can increase its quantity of stored fat in two ways 1) Fat cell hypertrophy- enlarging or filling existing fat cells with more fat 2) Fat cell hyperplasia- increasing the total number of fat cells - The major structural difference in adipose tissue mass between obese and non-obese people is in cell number - Typical fat cell numbers are as follows:  Average, non-obese person- 25-30 billion  Moderately obese person- 60-100 billion  Massively obese person- up to 200 billion - A decrease in the size of fat cells, with no change in the number of cells, accompanies weight reduction in obese adults and children - Although you cannot decrease the number of fat cells once you have them, you can increase the number of fat cells at any time in your life - Three critical periods when the number of fat cells increase significantly 1) During the last trimester of pregnancy 2) During the first year of infancy 3) During the adolescent growth spurt - Any undesirable life-style habits developed during childhood coupled with little exercise, will haunt us as adults - Number of fat cells becomes stable sometime before adulthood - Any weight gain or loss thereafter is usually related to a change in the size of the individual cells - There might be chances that alteration in fat cell size and number can be achieved by modifying early nutrition and exercise before adulthood SET-POINT THEORY - some people have difficulty in maintaining weight loss and understand the tendency of the body to “defend” its original weight - the tendency is referred to as set-point theory - set-point theory states that the body has an internal control mechanism, a set point, probably controlled by the hypothalamus in the brain, which drives it to maintain a particular level of body fat - when you manage to reduce your body fat below your natural set point, your body attempts to resist the change and conserve body fat by lowering your basal metabolic rate (BMR), which is the base level of your daily energy expenditure - when very low-calorie diets ( fewer than 800 kilocalories/day) are used, BMR may be decreased by as much as 45% - ^ greatly conserves energy and causes the diet to become much less effective - Different people have different set points - Drugs such as nicotine and amphetamine, as well as exercise, are some factors that may lower set point, whereas dieting appears to have much less of an effect SENSIBLE FAT LOSS (SLOW AND STEADY) - The net energy exchange that expresses the process of metabolism can be written as : - Caloric balance = kilocalories from food – (kilocalories of resting metabolism + kilocalories of physical activity + kilocalories used to digest food + kilocalories lost in excreta) - Kilocalories lost in excreta means that unless the food is digested, it should not be counted as “calories in” - It is possible to lose a small amount of weight initially by simply changing from refined carbohydrates to things like whole wheat or whole grain breads and pastas - The transit time for food in the gastrointestinal tract is reduced, so less is digested, and the bulk of fibre added to the meal reduces the ability of enzymes to digest food - The law of conservation of energy states that energy can be neither gained nor lost but only changed in form - A combination of decreased caloric intake and increased energy expenditure has the distinct advantage of accelerating weight loss - Daily caloric intake should not be less than 1,200 kilocalories on a regular basis - Any weight loss should be considered a temporary shift from having too much fat and having improved body composition - The goal should be to maintain that improved body composition - The generally recommended type of exercise program for weight control is one of continuous aerobic activity, preferably supplemented by resistance training - Sweating off calories doesn’t work because you are losing water, not fat, and you will regain this weight as soon as you rehydrate yourself - Fat does not sweat off and nor can it be mobilized by vibrating belts of bumping - Only negative caloric balance can do this - Exercise often reduces stress, boredom, and tension, and this can considerably reduce the amount of food consumed in response to stress - Anything that relieves stress is likely to be beneficial to improved body composition - Healthy food choices and exercises can become habitual in young children - When fat accumulation begins as a result of inactivity or overeating, it is important to start corrective efforts as soon as possible - High-carbohydrate foods tend to cause a quick blood sugar rise and then crash quickly and make you feel hungry sooner - Just eating slightly smaller portions is another simple way to make changes - Most people should avoid crash diet, as they do not encourage formation of good habits and they often result in a lower resting metabolic rate - With
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