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 Needs1. 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 hour3. 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 FEMALE160/2.2 = 72.7 kg 160/2.2 = 72.772.7 x 1=72.7 kcal. 72.7 x .9=65.4 kcal.72.7 x 24 = 1744.8 65.4 x 24 = 1570Kcal/day for BM Kcal/day for BMLight Activity Factor Light Activity Factor(1.6) (1.5)1744.8 x 1.6 = 2792 1570 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. Water b. Vitamins c. Nutrients d. Lymph

2. Of the following, which nutrient takes the longest to digest? a. Fat b. Sugar c. Vitamin C d. 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