Chapter Six: Metabolism and Energy Balance Define metabolism, anabolism and catabolism Explaining what is meant by the “protein sparing action” of carbo. Trace the energy release, building and storage steps of the energy nutrients. When are amino acids used for energy? How do excesses of the energy nutrients contribute to body fat.

Metabolism and Energy Balance cntd. Describe two ways in which the body spends energy Identify some of the factors that influence basal metabolism Estimate a day’s energy (kcaloric) needs Identify how fasting or starvation negatively affects the body

Metabolism Metabolism defined: the sum total of all chemical reactions in the body Metabolic Roles of the organs: Digestive organs: Digestion and Absorption (rapid cell turnover) Liver: most active metabolic organ— metabolizes, packages, stores, & ships nutrients Pancreas: secretes dig juices and insulin

Metabolic organs, cntd. Pancreas, cntd.: regulates body use of glucose Heart & Blood Vessels: transport nutrients and oxygen Kidneys: Filters waste products; regulates blood pressure; converts Vit D to active form

Body’s Energy Metabolism Basic Units of Energy Metabolism: Carbohydrate: Glucose Lipids: Glycerol & Fatty Acids Proteins: Amino Acids Results of catabolic reactions—releases energy—breakdown of compounds Results of anabolic reactions—uses energy—building of body compounds

Metabolic Reactions

Catabolic and Anabolic Reactions Involving Energy Nutrients Carbohydrate: Glucose used as energy Glucose converted to glycogen for energy storage Excess glucose converted to fat Fats: Triglycerides Glycerol & Fatty acids used for energy Glycerol used for energy or can be converted to glucose (5% of triglycerides) through process of gluconeogenesis--inefficient source of glucose

Release of Energy, cntd. Proteins Amino acids used to maintain, replace and build new cells Amino acids can be converted to glucose— not recommended but can be a back-up system (90% availability) through the process of gluconeogenesis

Body’s Energy Budget Feasting: Excess of any energy nutrient can lead to weight gain Glucose  Glycogen  Fat Fat  Fatty Acids/Glycerol  Fat Protein  Amino Acids  Fat Fasting/Starvation: Body reacts the same to fasting or starvation

Energy Budget, cntd. Liver Glycogen used first  Amino Acids & Glycerol second Ketone formation: After a few days the body uses fatty acid fragments from catabolism to form ketones Ketones can provide fuel for the brain and nervous system Metabolic rate slows to conserve energy

Hazards of Fasting Wasting of lean body tissue Impairment of disease resistance (antibodies depleted) Lowering of body temperature Disturbances of the body’s salt and water balance

Weight Reduction Recommendations Moderate energy restriction promotes a greater rate of weight loss, more fat loss, and retains lean tissue Maintaining Carbo intake protects protein from being used to make glucose—protein sparing fast

Measuring Kcalorie Needs Two Ways Energy is Used Fuel for Basal Metabolism (minimum needed for vital body processes) 2/3 of daily kcalories Fuel for Voluntary Activities (more control over this usage) 1/3 of daily kcalories

Metabolic influences, cntd. Factors Affecting Basal Metabolic Rate Physical activity Age Lean Body Mass Pregnancy Height Fever Thyroid Malnutrition (low kcalorie intake)

Estimation of Kcalorie Needs 1. Change pounds to Kilograms (Pounds / 2.2 = kg) 2. Multiply Weight in Kilograms by 1 for men and 0.9 for women to find kcalories used in one hour 3. Multiply kcalories used in one hour by 24 (hours in a day) 4. Multiply activity factor* by basal metabolic energy (determined in #3) to find total daily kcaloric needs. *You must determine at which of the five activity levels you are. (Most effective way to increase energy needs)

Estimating Energy Needs MALE FEMALE 160/2.2 = 72.7 kg 160/2.2 = x 1=72.7 kcal x.9=65.4 kcal x 24 = x 24 = 1570 Kcal/day for BM Light Activity Factor (1.6) (1.5) x 1.6 = x 1.5 = 2355

Problems with Ketosis Metabolism Slows Down Most of Weight Loss is water, glycogen, and lean muscle mass Excessive water loss = dehydration May cause mineral imbalances Risk of hypoglycemia and metabolic acidosis During pregnancy, can cause brain damage to the fetus

Possible Hazards of High Protein, Low Carbohydrate Diets Too low Carbs intake can lead to ketosis Excessive fat, especially saturated fat, and cholesterol intake Very low in fiber, potassium and phytochemicals Does not provide a balance of nutrients Too low in kcalories May stress kidneys May lead to calcium loss

Practice test questions What energy nutrients are digested in the small intestine? Water-soluble nutrients are released into what transport system? What are sources of glucose if it is not available from dietary carbohydrate?

Test Questions 1. One of the functions of the colon is to reabsorb: a. Waterb. Vitamins c. Nutrientsd. Lymph 2. Of the following, which nutrient takes the longest to digest? a. Fatb. Sugar c. Vitamin Cd. Iron

3. Three factors that affect the body’s basal metabolism are: A. Weight, fever, and environmental temperature B. Fever, body composition, and altitude C. Height, weight, and energy intake D. Age, body composition and fever

4. Carbohydrates are called “protein sparers” because the presence of an adequate amount: A. prevents the use of protein for energy B. Conserves essential fatty acids C. Prevents protein from being converted to fat D. None of the above