F2.Food

F2.Food - Diet & Nutrition Fate of Chemical Energy...

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Heyer 1 Malnutrition: "the cellular imbalance between supply of nutrients and energy and the body's demand for them to ensure growth, maintenance, and specific functions.” — World Health Organization Stages of malnutrition caused by excessive or inadequate intake of nutrients. Modified from Olson RE: "Pharmacology of nutrients and nutritional disease," in Principles of Pharmacology, edited by PL Munson. New York, Munson, Chapman, and Hall, 1995; in Merck Manual of Diagnosis and Therapy , 2004. Fate of Chemical Energy • Stored as – circulating energy substrates – body fat • Stored energy used for – 1) metabolism – 2) growth – 3) reproduction Regulation of Energy Metabolism • Energy reserves: – Molecules that can be oxidized for energy are derived from storage molecules (glycogen, protein, and fat). • Circulating substrates: – Molecules absorbed through small intestine and carried to the cell for use in cell respiration. Insert fig. 19.2 Food Energy • Measured in calories . – Physical definition of a calorie: “Upon combustion, the amount of heat energy released that will increase the temperature of 1 milliliter of pure water 1°C.” • Food energy reported in kilo calories (=1,000 calories). But food industry calls a kilocalorie a C alorie (“Big-C calorie”). • I.e., 1 Calorie = 1 kilocalorie = 1,000 calories 1 gram of carbohydrate or protein holds 4 Calories of food energy. 1 gram of lipid (fat/oil) holds 9 Calories . Energy Budget Balance between calories consumed in food and calories expended in metabolism Caloric expenditures: 1. Basal Metabolic Rate (BMR): energy expended by basic, resting body metabolism. ß Typically ~ 60% of total calories expended. 2. Adaptive thermogenesis: increased energy expended in response to: A.Environmental temperature B. Digestive activity (“specific dynamic action”) 3. Physical activity: increased energy expended by skeletal muscle activity. Energy Budget Balance between calories consumed in food and calories expended in metabolism If calories consumed < calories expended lose weight. If calories consumed > calories expended gain weight. Small amount of energy reserve stored as glycogen in liver and white skeletal muscle. Most stored as fat . Some in red muscle tissue, most in adipose tissue. ~3500 Calories = 1 lb of fat.
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Heyer 2 For example, … Say you’re a typical twenty-something person with a BMR = 1300 kcal/day. You’re also a typical sedentary student with an activity expenditure of 600 kcal/day. You try to go for an hour-long jog or bike-ride every day, = another 300 kcal. Based upon 10% of your intake, you can estimate your thermogenesis expenditure = 300 kcal/day. Thus your total typical daily caloric expenditure = (1300+600+300+300) = 2500 kcal/day.
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This note was uploaded on 09/02/2011 for the course BIOL 11 taught by Professor Heyer during the Fall '08 term at UCSD.

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F2.Food - Diet &amp; Nutrition Fate of Chemical Energy...

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