Energy Balance, Body Composition & Weight Management Readings: Chapter 9 Energy Balance • unbalanced energy budgets can lead to weight gain or weight loss • excess.
Download ReportTranscript Energy Balance, Body Composition & Weight Management Readings: Chapter 9 Energy Balance • unbalanced energy budgets can lead to weight gain or weight loss • excess.
Energy Balance, Body Composition & Weight Management Readings: Chapter 9 Energy Balance • unbalanced energy budgets can lead to weight gain or weight loss • excess energy beyond body’s needs increases fat storage • too little energy results in degradation of lean tissue to support energy needs • both extremes have serious health implications Energy Balance Maintaining weight means that: ENERGY IN ENERGY OUT Figure 8-1, page 242 Energy Intake Energy In = kilocalories from FOOD and DRINK How do we determine how much energy food provides? Bomb Calorimetry food is burned in an insulated chamber surrounded by water can measure: a) heat produced b) O2 consumed Energy Intake Limitations of Bomb Calorimetry • more efficient than human body Physiological Fuel Value = the number of kilocalories the body derives from a food (less than bomb calorimetry) Based on Food Composition • carbohydrates and protein provide 4 kcal/g, fat provides 9 kcal/g and alcohol 7 kcal/g Regulation of Energy Intake Recall from introductory Lecture • Hunger vs Appetite • the physiological drive for food that INITIATES food seeking behaviours • influenced by factors such as: – – – – Sensory Cognitive Environmental Health • triggered by chemical messengers acting on the HYPOTHALAMUS • satiation MORE SATIATING boiled white potatoes baked fish oatmeal with milk orange, apple whole grain pasta beefsteak, baked beans popcorn, eggs rice white bread snack chips, ice cream chocolate bar cake doughnuts croissant LESS SATIATING Energy Expenditure Thermogenesis • the generation of HEAT • used in physiology and nutrition studies as an index of how much energy the body is spending Components of Energy Expenditure • basal/resting energy expenditure • energy of physical activity • thermic effect of food • adaptive thermogenesis Physical Activity (25 – 35%) Thermic Effect of Food (5 – 10%) Basal/Resting Energy Expenditure (60 – 65%) Basal/Resting Energy Expenditure • the energy needed to maintain life when the body is at complete digestive, physical, and emotional rest • largest component of energy expenditure • measured as either basal metabolic rate (BMR) or resting energy expenditure (REE) Estimating REE: Harris-Benedict Equations Male 66 + (13.7 x weight) + (5 x height) - 6.8 x age) Female 655 + (9.6 x weight) + (1.8 x height) - (4.7 x age) Example: 20 year old male, weight = 70 kg, height = 175 cm = 66 + (13.7 x 70 kg) + (5 x 175) – (6.8 x 20) = 66 + 959 + 875 – 136 = 1,764 kcal/day Table 8-3, page 249; “How to”, page 250 Factors that Influence BMR increased lean body mass growth and pregnancy fever thyroid hormone (thyroxin) drugs such as caffeine, nicotine, amphetamines height stresses (e.g. diseases) environmental temperature (both heat and cold) increased age increased body fat sleep malnutrition starvation Table 8-1, page 247 Energy of Physical Activity • voluntary movement of the skeletal muscle and support system • most VARIABLE component of energy expenditure • amount of energy required for an activity depends on: – muscle mass – body weight – activity (intensity, duration, and frequency) Table 8-2, page 248 Energy of Physical Activity • can also estimate based on an activity factor which is then multiplied by the BMR (or REE) to estimate average energy expenditure Example: – activity factor for moderately active men = 45 65% of BMR (REE) – BMR (REE) from previous example = 1,764 – therefore total energy expenditure is 1,764 x 0.55 + 1,764 = 2734 kcal energy of physical activity BMR (REE) Table 804, page 250 Physical Inactivity • favours a positive energy balance • changes in lifestyle over the last century – sedentary work – sedentary recreation Thermic Effect of Food (TEF) • an estimation of the energy required to process food • includes energy needed to digest, absorb, transport, metabolize, and store food • proportional to the food energy consumed • estimated as: 5 - 10% of energy intake • influenced by meal size, frequency and composition Adaptive Thermogenesis • energy expended when an individual must adapt to change (e.g. stress, extreme cold, starvation, trauma) • extremely variable and highly specific • NOT included when calculating energy requirements What determines a healthy weight? Social perceptions? Health Risks? Hypertensio n Diabetes Arthritis CVD Body Mass Index (BMI) weight(kg ) BMI 2 [height(m)] < 18.5 18.5 - 24.9 25 - 29.9 > 30 underweight normal overweight obese Weakness of BMI? • does not account for body composition or body fat distribution • proportion of body weight that is FAT is more important for determining health risk Kevin Bieksa, BMI = 27.8 Body Composition • measurement of % body fat • techniques to measure include: – densitometry • underwater weighing • air displacement – – – – – – DEXA isotope dilution skin fold thickness bioelectrical impedance CT scanning or MRI near infrared interactance Body Composition Essential Fat • crucial for normal body functioning Non-essential Fat • most accumulates in VISCERAL adipose tissue Body Fat Distribution Android (Central Obesity) • apple shape • more common in men and post-menopausal women • associated with increased health risks Body Fat Distribution Gynoid (Lower Body Obesity) • pear shape • more common in premenopausal women • pattern encouraged by estrogen & progesterone Waist Circumference • reliable predictor of fat distribution and abdominal fat • measured around abdomen, just above crest of the hip Health Risks of Overweight • • • • • • • • • • cardiovascular disease (CVD) hypertension Type II Diabetes pulmonary disorders sleep disorders (e.g. SLEEP APNEA) gout hypertension various cancers osteoarthritis early mortality Health Risks of Underweight • • • • • • • nutrient deficiencies reproductive problems cardiac arrhythmias immunodeficiencies rough, dry, scaly skin poor temperature regulation osteoporosis and increased risk of bone fractures • early mortality Not the whole story… • body weight is only one risk factor of many for chronic disease • for example, also need to consider cardiorespiratory fitness – normal weight unfit men have more than 2x risk of all-cause mortality than normal weight physically fit men – overweight fit men have LOWER mortality risk than normal-weight unfit men Obesity • the second leading cause of preventable death after tobacco use • defined as an excessively high amount of body fat in relation to lean body mass – BMI > 30 – percent body fat > 25% (men) or > 32% (women) – waist circumference > 40” (men) or > 35” (women) Causes of Obesity Why do people consume more energy than they expend? Explanations are many… – genetic/physiological – environment • physical • cultural • socioeconomic • psychological Genetics Epidemiological Evidence • identical twins are 2x as likely to weigh the same compared to fraternal twins • if both parents are overweight a child is 2x as likely to be overweight compared to a child with only one overweight parent Physiology of Weight Gain • an excess energy consumption beyond the needs of the body results in energy being stored • the amount of fat in a person’s body reflects: – the NUMBER of fat cells – the SIZE of fat cells • definitions: hyperplastic and hypertrophic obesity Fat Cell Development • number of fat cells increases most during late childhood and early puberty • fat cell size increases as cells fill with lipids • after a fat cell reaches its maximum size, it may divide again • with fat loss, the SIZE of the cells decreases, but not the NUMBER Increase in fat cell size if energy intake exceeds energy expenditure Increase in fat cell number during growth With fat loss, the size of the fat cells shrinks, but not the number Increase in fat cell number when fat cells reach their maximum size Lipoprotein Lipase (LPL) • enzyme on adipose and muscle cells that captures triglycerides from blood and promotes storage of fat • since obese individuals have more fat cells, they have higher levels of LPL than lean individuals What does this mean for an obese individual who may only have a modest excess of energy intake? Lipoprotein Lipase (LPL) • activity of LPL is regulated by estrogen in women and testosterone in men Site of greatest LPL activity Women breasts, hips, thighs Effect on Body Fat Distribution gynecoid shape Men abdomen android shape • lower body is less active in releasing fat from storage • weight loss increases LPL activity Leptin • peptide hormone coded for by the Ob gene expressed in adipose cells • stimulates hypothalamus to produce melanocortins that inhibit appetite and promote energy expenditure thus promoting weight loss • low levels result in increased production of Neuropeptide Y by the hypothalamus promoting weight gain • levels increase with increased body fat; levels decrease with loss of body fat Leptin • RARE genetic deficiency of leptin leads to obesity • leptin concentrations increase with weight gain • most obese individuals have high leptin levels • suggests that obesity is associated with leptin resistance • leptin also has many other functions Neuropeptide Y The actions of neuropeptide Y include: – causes CARBOHYDRATE CRAVINGS – initiates eating – DECREASES ENERGY EXPENDITURE – INCREASES FAT STORAGE These each favour a positive energy balance and promote weight gain. Ghrelin • peptide hormone secreted by the stomach • acts on the hypothalamus to increase appetite by stimulating release of NPY Fad Diets Tell-tale Signs of a Fad Diet • • • • • • • • • • • promise dramatic weight loss promote diets that are nutritionally unbalanced promote extremely low energy intakes dependant on food products and services do not encourage permanent, realistic, lifestyle changes cost $$$$$ fail to inform clients about risks promote unproven weight loss aids and miracle foods rely on testimonials as evidence diet works don’t include exercise have lists of “good” and “bad” foods Why diets don’t work… The body DEFENDS itself against weight loss! Weight loss causes: • increased LPL activity • decreased thyroid hormone production • decreased leptin Why diets don’t work… Other Factors… • weight cycling • preoccupation with food, may lead to binge eating • often associated with irritability, depression, fatigue, poor concentration • does not resolve other issues such as low self-esteem, depression • may lead to social withdrawal • do not promote permanent healthy changes to lifestyle • unattainable weight loss goals can lead to frustration and failure Weight Cycling • repeated dieting which produces rapid weight loss is often unsuccessful Subsequent diet results in SLOWER weight loss Weight Regain Diet Regain Weight Gain Time Low Carb Diets Examples: • Dr. Atkin’s New Diet Revolution, Carbohydrate Addicts, others… Premise • consume less than 20 – 50 g of carbohydrate per day • no limit on fat or protein intake • promise rapid weight loss • appealing because allowed to eat high fat tasty foods Low Carb Diets Successful in promoting weight loss through three primary mechanisms: • low carbohydrate intake depletes glycogen stores leading to an initial rapid weight loss from water • low carbohydrate leads to production of ketones; the state of ketosis inhibits appetite and decreases energy intake • diets tend to be low in total energy intake and all diets that reduce caloric intake result in weight loss Low Carb Diets: Health Risks • nutritionally inadequate – risk deficiencies of Vitamin E, A, folate, calcium, dietary fiber and others • high in total and saturated fat – increases risk of CVD • causes ketosis and associated metabolic risks • dehydration – increased urine production to excrete by-products of protein metabolism • increased risk of kidney disease Treatment of Obesity • only 5% of individuals who successfully lose weight maintain their losses for at least a year Healthy Weight Loss Goals and Strategies • make SMALL changes • set REALISTIC expectations (for amount of weight loss within a reasonable time frame) Effective Weight Loss Weight loss is most effective if it: • is achieved GRADUALLY over time • embraces HEALTHY eating • incorporates PHYSICAL ACTIVITY A reasonable weight loss rate for overweight individuals is: – 0.5 – 2 lbs per week – 10% of body weight over six months Establish REALISTIC Goals • what are goals based on? – societal standards or physical attractiveness? – improved health and reduced risk of chronic disease? • a modest weight loss can still have health benefits even if an individual remains overweight • unattainable weight loss goals can lead to frustration and failure Develop a Healthy Eating Plan • severe energy restriction can have serious detrimental consequences • a minimum of 1200 kcal per day is required to maintain nutritional adequacy • reasonable suggestion: 500 kcal deficit per day – equivalent to about 1 pound per week (1 lb body fat = 3500 kcal) – achieve through combination of decreased energy intake and increased physical activity Tips for Eating Plans • eat small portions and eat slowly – satiety signal indicating fullness is sent after a 20 minute lag • focus on complex carbohydrates – such as fresh fruits, vegetables, legumes, and whole grains – high fiber foods contribute more to satiation and satiety • limit high fat foods – high fat meals lower blood leptin levels Tips for Eating Plans • limit empty calorie foods – includes high sugar and alcohol as well as fat • drink adequate water – need to meet water needs that were formerly provided by eating extra food – fills stomach between meals Incorporate Physical Activity • individuals who combine BOTH diet and exercise in a weight loss program are more likely to: – reduce body fat – retain more lean muscle mass – regain less weight Incorporate Physical Activity • Regular activity has many benefits • 200 kcal expenditure – – – – walking for 1 hour cycling for 30 min swimming for 20 min running for 15 min • Lifestyle change - activity habits and daily routine – quick walks, stairs, fidgeting Weight-Related Benefits of Exercise • short term increase in energy expenditure • long term increase in energy expenditure due to increased in lean tissue which increases BMR • improves body composition • helps with appetite control • decreases stress • improves self-esteem & psychological wellbeing Behaviour Modification Strategies • identify problem eating behaviours and develop alternate activities e.g. replace snacking while watching TV with going for a walk, stretching exercises, etc… • change the environment to reduce stimuli that encourage eating e.g. keep fridge stocked with fruits and vegetables instead of cookies, chips and crackers • identify the reason why you eat e.g. if stress, use exercise to relieve instead Behaviour Modification Strategies • monitor your habits e.g. what foods you eat, when ,where, and why you eat • develop supportive relationships with others or attend a support group • adopt permanent lifestyle changes to achieve and maintain a healthy weight Weight Maintenance • expect a plateau within about 6 months • important to continue with healthy lifestyle changes, including exercise • formerly overweight and obese individuals need less energy to support needs than individuals who have never been overweight due to: – increased efficiency at storing fat – lower BMR associated with weight loss Weight Maintenance Characteristics of Weight Loss Maintainers • lose weight slowly with small changes in eating and physical activity • consume regular meals • exercise regularly • make conscious efforts to avoid weight gain • change habits without depriving themselves of foods they enjoy • depend on social support • confront problems directly Weight Maintenance Characteristics of Weight Regainers • do not employ behaviour modification strategies • change diet radically to lose weight • do not include exercise as part of weight loss program • eat unconsciously in response to stress • take diet pills • lack social support • avoid problems rather than face them directly Aggressive Obesity Treatment: Drugs There is NO effective drug to treat obesity that can be used over time without adverse side effect or the potential for abuse! Sibutramine (Meridia) • inhibits uptake of neurochemical in the brain called serotonin • results in reduced appetite Aggressive Obesity Treatment: Drugs Orlistat (Xenical) • inhibits activity of pancreatic lipase to block fat digestion and absorption by 30% • taken with meals, most effective when combined with a reduced energy and low fat diet Benzocaine • anesthetizes the tongue & decreases taste • marketed under trade names of Slim Mints and Diet Ayds Surgery • limit food intake by reducing the size of the stomach