chapter16 - Energy Balance = body weight will remain...

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Energy Balance = body weight will remain constant if energy in = energy out aka neutral energy balances Majority of food energy is used for body heat Body converts most food energy into heat Energy of ingested food = energy input Energy released from broken bonds in food molecules is used to make ATP Energy from ingested nutrients immediately performs work or stores it in body for future Energy Output 1. External Work = skeletal muscles move external objects 2. Internal Work = expenditure of energy that doesn’t accomplish mechanical work outside body (metabolism) Energy from nutrients doesn’t perform work is converted to heat (60%) Heat energy cant be used to perform work (40% of nutrient energy transferred to ATP) Internal Work Internal work = energy used to keep body alive - Pumping blood - Nerve activity - Cell transport - Production of cellular parts = BMR uses majority of our daily caloric needs (60-70%) The Metabolic Rate = Rate of Energy Used Most of energy expenditure of body eventually appears as heat Rate expressed as rate of heat production in kcal per hr Metabolic rate is measured under standardized basal conditions BMR Measured Under Stringent Conditions Must fast, rest, comfortable temp, lay down, good health, and awake Controlled and unnatural RMR = Resting Metabolic Rate Estb the min # of cals necessary to sustain body functioning for 24 hrs w/ no activity 10% higher than BMR RMR + calories to do external work = total day energy expenditure Energy Balance Neutral: energy in = energy out Positive: energy in greater than energy out (fat) Negative: energy out greater than energy in (weight loss) must used stored energy Food Intake is Controlled Primarily by Hypothalamus Has feeding centers for hunger and satiety Centers communicated w/ multiple, highly-integrated pathways sending signals in/out of hypothalamus The neural centers respond to numerous chem. changes in blood (ie glucose
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chapter16 - Energy Balance = body weight will remain...

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