Nutri Sci Ch. 7 - Brian Oliver March 2, 2008 Chapter 7:...

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Brian Oliver March 2, 2008 Chapter 7: Energy Balance and Body Weight An Ecological Perspective 1. some people put on fat more easily than others 2. thrifty metabolism: energy efficient metabolism, requiring few calories for daily activities; genetically determined; contributes to modern obesity a. Pima Indians of Arizona/Mexico i. Arizona desert is dry, and food is sparse ii. Food preservation is hard in a 120 degree environment iii. People had to take surplus food when they could, and store it as fat iv. Only people with thrifty metabolisms could survive v. Body fat made life possible vi. Today over 50% of Pima Indians are obese (different environment) b. We still retain the ability to put on body fat- part of our ecosystem Overview of Macronutrient Metabolism 1. Anabolism a. anabolism: body processes that create more complex chemical compounds for energy storage or for the synthesis of tissue b. “the body building itself” c. pregnancy, infant growth, weight gain, muscle building d. glycogen synthesis – glycogen made from glucose e. protein synthesis – protein from amino acids f. triglyceride synthesis g. any macronutrient, eaten in excess, will be converted into triglyceride and stored as fat in the adipose 2. Catabolism a. catabolism: body processes that break down complex chemical compounds for energy release or for tissue breakdown b. “the body breaking itself down” c. Exercise, fasting, physiological stress d. Adenosine Triphosphate (ATP): high energy chemical compound used to transfer energy from nutrients to various life processes i. Carries energy from food to cell ii. Produced from blood sugar, muscle glycogen, body fat, or muscle protein e. Anaerobic metabolism (high intensity exercise) i. Energy produced without oxygen ii. Glucose converted to lactic acid to produce ATP iii. Fat can’t be used as fuel f. Aerobic metabolism (lower intensity exercise) i. Oxygen is used for energy production ii. Carbs, fatty acids, amino acids used as fuel iii. Fat can be used as fuel 3. Fate of a Bowl of Oatmeal a. Protein and milk incorporated into muscle growth stimulated by yesterday’s exercise b. Starch and brown sugar burned in today’s exercise c. Fat taken up by muscles for present use i. Carbs and fat can be used as muscle fuel ii. It would be converted to fat without the exercise d. Fat only supports lower intensity exercise e. Fasting defeats the muscle building benefit of exercise i. More muscle loss than fat loss (catabolism/gluconeogenesis)
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Energy 1. conservation of energy a. sun’s nuclear energy captured by plants through photosynthesis b. starch broken down by digestive system into sugar c. stored as glycogen and fat, and released into blood d. all our energy comes from the chemical energy in food (solar energy) e. 1000 calories = 1 kilocalorie 2. efficiency of conversion a. some energy is always lost as heat when chemical energy converts to mechanical energy 3. energy balance a. we can tell whether we’re gaining/losing energy by whether we’re gaining/losing weight
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Nutri Sci Ch. 7 - Brian Oliver March 2, 2008 Chapter 7:...

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