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Energy Balance
Department of Medical Nutrition
By
Gaga Irawan Nugraha, MD., MS.
Energy: Fuel for Work
Energy sourceChemical energy in carbohydrates, fat, protein
Food energy to cellular energyStage 1: digestion, absorption, transportStage 2: breakdown of molecules Stage 3: transfer of energy to a form cells can
use
Cell is the metabolic
processing center Nucleus Cytoplasm
Cytosol + organelles
ATP is the body’s energy currency ATP = adenosine triphosphate Form of energy cells use
NAD and FAD: transport shuttles Accept high energy electrons for
use in ATP production
Metabolism is an integrated set of chemical reactions occuring in the body that enable us to extract energy from the environment and use it to synthesize building blocks that are used to make essential proteins, carbohydrates and lipids.
Fundamental points about metabolism: Each reaction does not occur in
isolation but provides a substrate. Pathways producing a continuous
process. Metabolic map. Some of the reactions are one way. Concepts & purposes of reactions.
CatabolismReactions that
breakdown compounds into small units
AnabolismReactions that build
complex molecules from smaller ones
Metabolism pathways can be classified as either catabolism or anabolism.
Catabolism pathways names end is lysis meaning to breakdown.
glycogenolysis: glycogen breakdown
proteolysis: protein breakdown
lipolysis: lipid breakdown
glycolysis: glucose breakdown
Anabolic pathways names end in genesis meaning to create.
glycogenesis: glycogen synthesis
lipogenesis: fatty acid synthesis
gluconeogenesis: glucose synthesis
protein synthesis
The transfer of energy in reactions: when chemical bond breaks, energy can be released as heat, captured in another chemical bond, or both.
The site of reactions: metabolic work is going on all the time within the cells.
Catabolism of energy-rich compound (carbohydrate, protein & fat): anaerobic reactions (cytosol) aerobic reactions (mitochondria)
Regulations of pathways: metabolic reactions almost always require enzyme (or hormone) to facilitate their action. Enzymes need coenzymes. The enzymes are subject to strict regulation to ensure that:
The rate of the pathway is adapted to the cell’s needs.
Anabolic & catabolic pathways are not active at the same time.
Production of H2O & Energy in the mitochondria:
The energy potential produced, could form high energy phosphate molecules (ATP & GTP)
ADP + phosphate + energy ATP
GDP + phosphate+ energy GTP
H2 + O2 H2O+ energy
Each organ has a preferential fuel; that is, the substrate that it prefers to use for energy production.
Glucose: brain, red blood cells, adrenal gland and muscle in anaerobic activity and high intensity aerobic activity.
Fatty acids: heart, liver, smooth muscle and skeletal muscle in low intensity aerobic activity.
Ketone bodies: heart, skeletal muscle and after adaptation of starvation, by the brain.
Branch chain amino acids (BcAA): skeletal muscle.
Other amino acid: liver.
Breakdown and Release of Energy
Extracting energy from carbohydrateGlycolysis
Pathway splits glucose into 2
pyruvates Transfers electrons to NAD Produces some ATP
Pyruvate to acetyl CoA Releases CO2
Transfers electrons to NAD
Breakdown and Release of Energy Extracting energy from carbohydrate
Citric acid cycle Releases CO2
Produces GTP (like ATP) Transfers electrons to NAD
and FAD Electron transport chain
Accepts electrons from NADand FAD
Produces large amounts of ATP Produces water
End products of glucose breakdown
ATP, H2O, CO2
Extracting energy from fatSplit triglycerides into glycerol and fatty acidsBeta-oxidation
Breaks apart fatty acids into acetyl CoA Transfers electrons to NAD and FAD
Citric acid cycle Acetyl CoA from beta-oxidation enters cycle
Electron transport chainEnd products of fat breakdown
ATP, H2O, CO2
Breakdown and Release of Energy
Extracting energy from proteinSplit protein into amino acidsSplit off amino group
Converted to urea for excretion
Carbon skeleton enters breakdown pathways
End products ATP, H2O, CO2, urea
Breakdown and Release of Energy
Breakdown and Release of Energy
The breakdown of high energy phosphate molecules will occur if the cells need energy.
ATP ADP + Energy
Functions of the energy released: to conduct nerve impulse (electric) actin & myosin contraction (mechanic) transfer of molecules across membrane
(osmotic) to produce heat (thermic) anabolism (chemical)
Biosynthesis and Storage
Making carbohydrate (glucose) Gluconeogenesis
Uses pyruvate, lactate, glycerol, certain amino acids
Storing carbohydrate (glycogen) Liver, muscle make glycogen from glucose
Making fat (fatty acids) Lipogenesis
Uses acetyl CoA from fat, amino acids, glucose
Storing fat (triglyceride) Stored in adipose tissue
Biosynthesis and Storage
Making ketone bodies (ketogenesis)Made from acetyl CoA
Inadequate glucose in cells
Making protein (amino acids)Amino acid pool supplied from
Diet, protein breakdown, cell synthesis
Regulation of Metabolism
May favor either anabolic or catabolic functions
Regulating hormones InsulinGlucagonCortisolEpinephrine
Special States
FeastingExcess energy
intake from
carbohydrate, fat, protein
Promotes storage
Special States Fasting
Inadequate energy intake
Promotes breakdown
Prolonged fasting
Protects body protein as
long as possible
ENERGY BALANCE
Key Term:
Energy intake
Energy expenditure
Energy requirement
Energy balance
Equilibrium of energy intake and energy expenditure determine the energy status.
Energy st. assessment for children weight for age.
Energy st. assessment for adults weight for height: Body Mass Index (BMI).
ENERGY
EXPENDITURE
ENERGY
INTAKE
ENERGY STATUS
Balanced energy: if energy intake sufficient with the energy expenditure.
Surplus of energy: if energy intake larger than energy expenditure energy storage increase:CH stored as glycogen (limited) and
as lipid (abundance).Fatty acids stored as lipid.Protein stored as lipid.
Energy deficit = if energy intake insufficient for energy expenditure. Storage molecules will be used.
7 Kkal of energy similar to 1 gram of body tissue.
Loss of energy: 500 Kkal/day or 3500 Kkal/week catabolism of body tissue: 3500 : 7 = 500 g body tissue/week.
Energy intake obtain from the food.
Various amount of energy in the food, depends on the composition of the foods.
1 gram CH 4 Kkal
1 gram Protein 4 Kkal
1 gram fatty acid 9 Kkal
Vitamin, mineral and water do not provide adequate energy.
Daily amount of energy intake depends on: food class, quantity per portion, and frequency of food intake per day.
Nutrient composition & amount of energy per 100 gram food stuff are available in Food Composition List. Food stuff weight comes from Household measurement.
Total Energy Expenditure = TEE : sum of Basal Energy Expenditure (BEE), Physical Activity (PA) and Spesific Dynamic Action of food (SDA) or Thermic Effect of Food (TEF).
The calculation:
TEE = BEE + PA + SDA (TEF)
BEE is energy expenditure in basal condition , the ongoing activity while the body rest: heart beat, peristaltic, hormone secretion, enzyme secretion, muscle contraction, etc.
Basal condition: 12 – 16 hours after the last meal Lying position No physical activity an hour before the
test Relax Normal body temperature Room temperature should be 21-25oC Normal humidity
Harris & Benedict calculation for BEE:
Simple calculation for BEE:
Men : 66 + (13,7 x BW kg) + (5 x BH cm) – (6,8 x age)Women: 665 + (9,6 x BW kg) + (1,7 x BH cm) – (4,7 x age)
Men : 1 Kkal / BW Kg / h = 24 Kkal / BW Kg / dWomen: 0,9 Kkal / BW Kg / h = 21,6 Kkal / BW Kg/ d
Factors that influence BEE
Body weight, height, age, gender, growth, temperature, muscle mass, sleep, endocrine activity, nutrition status.
Age : above 20 BEE will decrease 2% every 10 y.
Gender : BEE in men > women (at age >10 y)
Growth: highest for baby and adolescence.
Height: the taller the higher BEE
Muscle mass : the greater the higher BEE
Temperature : every 1oC elevation of body temperature (body temp above 37oC)
BEE will increase 13%
Sleep : BEE decrease 10%
Endocrine :- hiperthyroid: BEE increase
75-100%
- hipothyroid : BEE decrease
30-40%
- right before menstruation BEE slightly increase and during menstruation BEE decrease
Nutrition status : BEE decrease in PEM
Pregnancy : BEE increase 15-25%
Physical Activity (PA)
PA very light = 10-30% BEE PA light = 30-50% BEE PA moderate = 50-80% BEE PA heavy = 80-100% BEE AF very heavy = > 100% BEE
Level of Activity Very light: - Activity in sitting position
- Bedrest Light: Teacher, lecturer, general
practitioner, housewife. Moderate: Farmer, student(+ sport),
office worker Heavy : Athlete during TC, unskilled
worker, manual laborer, army during training
Very heavy : Sawyer of wood,blacksmith, ricksaw carrier, becak driver.
SDA or TEFSDA /TEF is the amount of energy used
for digestion, absorption and utilization of food consumed.
- SDA of protein 30% BEE
- SDA of carbohydrate < protein
- SDA of fat the lowest
SDA of Indonesian food on the average is 10% of BEE + AF