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