Energy Balance and Body Composition Chapter 8 !Fasting/Feasting Review: Too little energy in the diet… Fat used for energy!lean tissue used to meet glucose and protein needs trend is towards losing weight (either in fat or lean tissue) !Too much energy from food is stored as fat: Fat used for energy between meals/famine Weight gain !Energy Balance Energy balance- energy (kcal) Energy balance is energy in = energy out • Energy balance – energy (kcal) consumed from foods and beverages compared with the energy expended through metabolic processes and activities • Energy balance: energy in = energy out • A shift in balance causes weight changes • Not simply fat changes (proteins attract water, lose protein and glycogen, lose weight) Carb loading will gain weight, then lose again as mostly water after the race Water (60% of body wt) retention or loss Long-term, ~ 75% fat, 25% lean (safest and longest lasting) Starvation, ~ 50% fat, 50% lean (breakdown of protein is happening, shift towards more of muscle because need glucose and amino acids) •1 pound of fat = 3500 kCalories in time of need/long term (deficit of 3500 calories, lose a pound of fat) !Measuring energy released from food: • Direct Calorimetry - bomb calorimeter (direct measurement of what the food provides- exact) • measure heat as energy • Indirect Calorimetry (end products are co2 and h2o, addition of oxygen to products and then as exhale, can measure how much of that oxygen was consumed) how much we used, not what the food provided • measure oxygen consumption by face mask or canopy hood • kCalorie calculations- !Food Composition • Physiological fuel value – (what we get from the good vs. what it gave) the number of kCals that the body derives from a food (not the number of kcal provided by a food, as determinedfrom bomb calorimetry) - we don’t get 100% of our energy from out food, we use some for metabolism • Differs from measurements of food composition •Can correct with mathematical formulas to provide tables!• Still only an estimate (not exact) !8.1 and 8.2 Review: • What is physiological fuel value? How much energy (# of kCals) we get from food • Three different methods (and instruments if applicable) that can be used to determine the energy provided by food or food composition are: 1. Direct Calorimetry (bomb calorimeter) 2. Indirect Calorimetry (face mask or canopy hood) 3. kCalorie calculations !•Describe the accuracy and/or variability of these methods: all an ESTIMATE. Can not be exact !Energy In: Food Intake • Appetite – integrated response to sight, smell, thought, or taste of food that initiates or delays eating (feeling/want) • Hunger – sensation caused by a lack of food that initiates food-seeking behavior (physiological response) • Physiological response to nerve signals and chemical messengers originating and acting in brain • Hypothalamus (acting here- brain’s center for food) • Influences on hunger • Presence or absence of nutrients in bloodstream • Size and composition of preceding meal • Customary eating patterns • Climate (heat↓, cold↑) • Physical Activity • Hormones (insulin and glucagon) • Illnesses (i.e. stomach virus) !•Satiation – what signals that we stop eating – determines amount in meal !• During meal,food enters GI & satiation occurs • Receptors in stomach stretch • Hormones(i.e.Cholecystokinin/CCK)active • Begin feeling full and prompted (might override this) to stop eating • Satiety – not to start eating again – determines time between meals • 4 hours after a meal, most or all of food leaves stomach, emptiness of stomach influences hunger/satiety!•Influencing satiation and satiety! • Nutrient composition • Protein is most satiating, vs. fructose* • Low-energy density – satiating (because of volume, fills up the stomach) • High-fiber foods – satiating by filling stomach (stretch receptors) • Studies that show: Eating salad before meal can reduce total kcal intake (high fiber, low energy density) • High-fat foods • Weak satiation signal – can passively overeat (easier because can’t sense the satiation signal really) • Strong satiety (feel fuller longer) signals – triggers CCK release (less scientific level: fat travels slower, so more time before feel hungry) !• The hypothalamus • Control center for eating * • Integrates messages: • about energy intake, expenditure, storage (of fat, of glucose) • from mouth, GI tract, and liver (messages from here), hypothalamus puts that all together and gives us that feeling !Gastrointestinal hormones that regulate food intake • Amylin • Cholecystokinin*- activated because slows the movement of food through the digestion tract when fat enters the intestine • Enterostatin • Ghrelin • Glucagon-like peptide -1 (GLP-1) • Oxyntomodulin • Pancreatic Polypeptide (PP) • Neuropeptide Y*– causes CHO cravings, initiates eating, ↓ energy expenditure, ↑ fat storage; these factors support positive energy balance and weight gain (what can we do to suppress it?) • Peptide YY (PYY) !8.2 - Energy In Review •Appetite is a feeling/craving/desire to eat. Perception •Hunger is a physiological reaction/sensation need/signal to eat. •Satiation is: the signal that the body sends for the person to stop eating because the body is full •Satiety is: how long your fullness can last/how long you’re told you have enough/ reminder to not start eating againOverriding hunger, satiation and satiety • Emotional, Environmental, Cognitive, Disordered eating Examples: illness, tastes good, stress (too stressed to eat, so stressed all I want to do is eat), social cues, body image, abundance of food (buffet), medication, emotions, climate, smell (good/bad), memories, perceptions !Review: Energy In- Food Intake •What is the hypothalamus? Food control center in the brain •Describe the action of 2 of the hormones involved in hunger, cholecystokinin and neuropeptide Y Cholecystokinin- slows down food movement in GI tract when fat is present in the intestine Neuropeptide Y- Makes people crave carbs, initiates eating, increases fat storage, support positive energy balance and weight gain !Energy Out • Thermogenesis - generation of heat; used as index of how much energy body is expending • 3
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