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Chapter 8 - Energy Balance.doc

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Queen's University
Health Studies
HLTH 230
Jeffery Lalonde

Chapter 8 - Energy Balance Energy Balance • energy in = energy out (body weight is stable) • energy in > energy out (body weight increases) • energy in < energy out (body weight decreases) • excess protein, carbs, fat, alcohol can lead to increased body fat -we don’t eat consistently throughout the day With Excess Energy... Macronutrient Broken into Stored Carbs Glucose Glycogen stores Body fat stores Fat Fatty Acids Body fat stores Protein Amino Acids Body fat stores • individuals are constantly burning energy, even at rest (Basal Metabolic Rate; BMR) • we eat to “refuel” • when energy we refuel does not equal energy expended, weight will change if food intake is 3500 kilocalories greater than expenditure => gain 1lb of fat • • healthy weight adult will have energy stores between 50,000 and 200,000 kcal (only 1500-2000 kcal from glycogen, both liver and muscle) Twinkie diet helps nutrition professor lose 27 pounds • out to prove energy equation • normally eats 2600 kcal a day, but then ate 1800 calories a day (all junkfood) • lost weight!! (energy in < energy out = weight loss. ONLY CALORIES that matter) Chapter 8 - Energy Balance Kcalorie vs. Kilojoule (don’t ned to know) • 4.184 joules = energy needed to increase 1g of water by 1 degree Celsius 1kcal = 4.184 kJ • • a quick change in body weight is not a change in body fat -24 hr miracle diet: effectively lose up to 5 lbs in just 24 hours! -5 lbs x 3500 kcal = 17 500 kcal needs to be expended ~ 6 marathons! *diuretic that makes you lose water, 2L of water = 4.2 lbs • change in amount of fluid in the body is responsible for rapid weight change -glycogen is very hydrophilic -water balance -salt intake Weight loss • long term weight loss: weight loss generally 75% fat + 25% lean tissue (slight caloric deficit) • starvation/very rapid weight loss: generally 50% fat, 50% lean tissue (severe caloric deficit) • fat losses and gains are gradual Rapid Weight Loss - “Yo-yo” effect • starvation experiment • 24 weeks of starvation • after week 24 - gradual refeeding • Week 12 of Reeating - can eat whatever they want to eat -over ate to recompensate for when they weren’t eating -2 interesting things that happened: -when fat mass returned to normal, they started to eat normally -when fat free mass returned to normal, amount of calories they ate returned back to normal *fat mass and fat free mass have influence on eating when it comes to weight loss and weight gain Basic Chemistry - Energy In • food and drink provide energy • calorie content of foods -burn food in a bomb calorimeter -when food is burned, chemical bonds between carbon + hydrogen atoms break -> releases energy in form of heat (direct calorimetry) -overstates amount of energy the human body gets from foods. Why? -human body is not 100% efficient, some energy lost as heat -an equation is used to adjust for this overstatement -CO2 and water a produced -amount of O2 used gives an indirect measure of heat produced (indirect calorimetry) Chapter 8 - Energy Balance Calorie Contents of Food (Caloric Density) • energy value of foods can also be calculated by calculating fat, carbs, protein, alcohol in food 1g of CHO = 4kcal • • 1g of protein = 4kcal • 1g of fat = 9kcal • 1g of alcohol = 7kcal Energy Calculation from Macronutrient Content Ex. hungry man dinner fat: 64g x 9kcal/g = 576kcal carb: 74g x 4kcal/g = 296kcal pro: 36g x 4kcal/g = 144 kcal total = 1016 kcal Food Intake Regulation - Energy must be regulated • appetite: integrated response to sight, smell, thought, taste of food that initiates/delays eating -prompts a person to eat/not eat -can be experienced without hunger -favourite dessert after a big meal -sight and smell of dessert triggers appetite, not hunger • opposite is also true -> may be hungry, but will not have appetite if worried or tired of eating • hunger: irritating “painful” sensation caused by lack of food that initiates food-seeking behav. -triggered by chemical messengers initiating + acting in the brain (mainly hypothalamus) -can be influenced by: -Presence/absence of nutrients in blood -people getting nutrients through IV don’t feel hunger -Size and composition of preceding meal ->Gastric emptying (time it takes for stomach to empty) -Lipids and Fibre (delay hunger) -Climate -> cold increases intake, heat decreases intake -Customary eating patterns -> Thanksgiving, Christmas, Holidays -> other people -> usual timings (always eating at 5pm) -Exercise -> increases need for macronutrients (refuel) -Hormones -Physical illness -Mental illness ***OREXIGENIC: to stimulate or increase appetite (ex hormone, medication) ***ANORECTIC: something that suppresses appetite Chapter 8 - Energy Balance • stomach is a reservoir that handles periodic amounts of foods • most food has left stomach after 4 hours • most people do not feel like eating until stomach is empty/almost empty satiation: feeling of satisfaction and fullness that occurs during a meal, and halts eating -determines how much food is consumed at a meal -receptors in stomach stretch -> person begins to feel full -> satiation occurs -> person stops eating satiety: feeling of satisfaction after a meal, inhibits eating until next meal -determines how much time passes between meals -often over ridden -appetite for favourite food -stressful situation satiation -> tells us to stop eating satiety -> tells us not to start eating again -regardless of hunger, people typically overeat when offered the abundance and variety of an “all you can eat” buffet Sensory Specific Satiety (SSS) • concept that we tend to get bored of a food as we eat it • the more variety there is, the more likely it is that we will increase overall consumption *pleasantness of food eaten decreased more than that of foods not being eaten => satiety can be partly specific to foods eaten, specificity may be an important determinant of foods selected for consumption Study -pleasantness of food eaten at lunch decreases more of foods not eaten -people were bored of what they ate at lunch, decreased pleasantness of the food • Overriding Hunger and Satiety -food cravings when bored -eat when celebrating -eat when stressed -eating more with variety and large portions -discipline can lead us to ignore hunger -eating disorders -not eating when excited -not eating when stressed Chapter 8 - Energy Balance Portion Size Does Matter • people given stale popcorn still ate 33.6% more popcorn when eating from a large container than from a medium-size container • silver lining -> portion size can also be used to increase the consumption of less preferred healthful foods, such as raw vegetables American Journal of Clinical Nutrition • increase in prevalence of obesity has coincided with an increase in portion sizes • data indicates that portion size does influence energy intake • despite increases in intake, individuals presented with large portions generally do not report or respond to increased levels of fullness • one strategy to address the effect of portion size is decreasing the energy density of foods studies have demonstrated that eating low-energy-dense foods (fruits/veg/soups) maintains • satiety while reducing energy intake -eating more volume with less calories Increasing Portion Sizes -some people always clean their plates -some people always empty their bowls What happens if a bowl never empties? Bottomless Bowls • 54 participants, divided into 2 groups -thought they were doing a study on colour and appetite • actually testing: -4 people at a table, 2 bowls were subtly refilled -biased visual cue consumed 73% more soup but didn’t report being any more full even though they ate more Satiety and Satiation Continued • Sustaining Satiation and Satiety -ability of a food to produce satiation and sustain satiety depends on the nutrient composition -protein is the most satiating energy yielding nutrient -foods rich in fibre also effectively provide satiation by filling the stomach and delay gastric emptying prolonging satiety -fructose in sugary fruit drink may stimulate appetite and increase intake • Fat has a weak effect on satiation (not a lot of volume to it, doesn’t fill up stomach) • high fat foods are flavourful increasing appetite and are also energy dense • fat provides little satiation during a meal, but it produces strong satiety signals after a meal when it reaches intestines • fat in the intestine triggers release of CCK which signals satiety Chapter 8 - Energy Balance *protein + fibre = eat less *fructose = eat more General Guidelines • high fat foods must be eaten in small portions compared to fibre rich foods, like veg., fruits, whole grains which provide volume • portion size correlates directly with a foods satiety Figure 8-3 Figure 8-2 nuts = 100 cal popcorn = 100 cal nuts have a high fat content - energy dense Hypothalamus • the “control centre” or “Message Central” • integrates messages about energy intake, expenditure and storage from other parts of the brain, the mouth, the liver, and GI tract Dozens of chemicals in the brain participate in appetite control and energy balance • *****ex. Neuropeptide Y: favours positive energy balance (orexigenic)****** -initiates eating -causes carbohydrate cravings -decreases energy expenditure -increases fat storage Food Intake Regulation Gastrointestinal Hormones that regulate food intake (don’t need to know except Ghrelin) • -Amylin -CCK -Enterostatin -Ghrelin -GLP-1 -Oxyntomodulin -Pancreatic Peptide (PP) -Peptide YY (PYY) Energy Out (Figure 8-4) thermogensis: breaking down energy yielding nutrients -> produces heat -total body energy expenditure -BMR -PA -Food consumption -sometimes: adaptation (ex. climate, stress, trauma) Chapter 8 - Energy Balance BMR • Basal Metabolism -approx. 2/3 of energy expended by an average person per day -Metabolic activities include -maintaining body temperature -breathing -circulation -making RBC, tissues, etc. • BMR: rate at which body expends energy to maintain vital functions when the body is at complete digestive, physical, emotional rest • the more a person weighs -> the greater the amount of energy expended on basal metabolism -but amount of energy expended per round may be lower Example: -150lb adult has a higher metabolic rate than a 15lb baby -per pound, the baby has a higher metabolic rate *150 lb person is going to burn more calories/hour than baby but if looked at per/lb basis, baby is burning more calories/plb • BMR is higher in: -people who are growing (children, pregnancy) -people with more lean muscle mass (physically fit people) -lean body mass: the weight of the body minus fat -Fever & Illness -Resting Energy Expenditure increases approx. 8-9% in HIV+ men, even with normal CD4+ counts compared to control subjects. In patients with AIDS, metabolic rate increases by 21% and if an opportunistic infection is present, REE increases dramatically to 34% -During stress -Hyperthyroidism (hypothyrodism will do opposite) -Caffeine -Smoking -Environmental temperatures (cold temperatures) • slows down with -fasting -body attempts to conserve fuel stored -undernutrition -age ~2%-5% muscle loss/decade -sarcopenia - muscle loss due to age • Basal Metabolic Rate: rate of energy use for metabolism under specific conditions -after a 12 hour fast and a restful sleep Chapter 8 - Energy Balance -without physical activity/emotional excitement -in a comfortable setting • Resting Metabolic Rate -similar to BMR, a measure of energy use of a person at rest in a comfortable setting but with less stringent criteria for food intake and PA -RMR generally higher RMR > BMR because less strict on fasting and rest Physical Activity (PA) - 35% • voluntary movement of the skeletal muscles and support systems • most variable and changeable component of energy expenditure • extra energy is required to move and the heart and lungs require extra energy • how much extra energy is required will depend on: -person’s weight -muscle mass -activity being performed...intensity & duration Thermic Effect of Food (TEF) - 10% - energy it takes to digest food • when a person eats, GI tract muscles speed up their activity • increased energy produces heat -> Thermic Effect of Food • TEF: total amount of energy needed to digest, absorb, metabolize and store the food you eat • generally estimated at 10% of intake • TEF is higher for a meal eaten all at once, than spread out over a couple of hours generally TEF is not counted • • negative calorie foods? no solid research -like celery -idea is closely tied to low energy density (foods with a lot of volume and fibre but not a lot of calories) Fat 0-5% • • Carbohydrate 5-10% • Protein 20-30% - HIGHEST THERMIC EFFECT ON FOOD • Alcohol 15-20% Adaptive Thermogenesis • additional energy expenditure when body is dramatically challenged (
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