physiology of starvation
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8/4/2019 Physiology of Starvation
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DR. PARAS PAREKH
1ST YEAR RESIDENT
DEPARTMENT OF PHYSIOLOGY
B.J. MEDICAL COLLEGE
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Starvation is the result of asevere or total lack of
nutrients needed for themaintenance of life.
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Severe reductionin vitamin, nutrient and energyintake.
Most extreme formof malnutrition. In humans, prolonged starvation can
cause permanent organ damage andeventually, death.
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Fasting is refraining fromeating and drinking, for certain
period of time. Can be done for a day toseveral weeks.
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Used for thousands of years, fasting is one of
the oldest therapies in medicine
Many of the great doctors of ancient times
and many of the oldest healing systems have
recommended fasting as an integral method
of healing and prevention
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Fasting has also been used in nearly every religion
in the world, including Hinduism, Christianity,
Buddhism, and Islam. Many of history's great
spiritual leaders fasted for mental and spiritual
clarity, including Jesus, Buddha, and Mohammed.
In one of the famous political acts of the last
century, the Indian leader Mahatma Gandhifasted for 21 days to promote peace
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In ancient times, Starvation wasused as a DEATH SENTENCE.
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On the basis of intake of food…
1) Dry fasting. Absolute Fast, Black Fast, and HebrewFast.Most extreme
Has spiritual rootsConsists of foregoing food and waterfor short periods.
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2) Liquid fasting.
Fasting on liquids only.
Water fasting Simplest and perhaps the oldest form.Delivers the greatest level of
therapeutic benefit physically and in ashort period of time. Juice fasting
Extremely popular.Nutritional support in a pure andnatural form.
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Foods
Protein Polysaccharides Lipids
Aminoacids Mono & Fatty acidsDisaccharides Glycerol
Glycolysis
Pyruvate
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Acetyl CoA
NADHElectron transport
& Oxidative
O2 Phosphorylation
NH3 H2O ATP + NAD CO2
Citricacidcycle
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During metabolism, first there is a hydrolysisof macromolecules to their subunits.
Conversion of subunits to acetyl CoA andproduction of a small amount of ATP andNADH.
Oxidation of acetyl CoA to water and carbondioxide
Considerable amount of ATP is produced.
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Liver glycogen is first mobilised,
Gluconeogenesis from glucogenic amino acids
and later on from other substrates also.
Last for not more than 2 to 3 days.
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Major part of energy is derived from Fats ofadipose tissue and remaining from Proteins.
Last longer,usually over two weeks becauseadipose tissue represents the largest amountof stored food.
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Fat stores are almost exhausted so energy isobtained from the breakdown of tissue protein.
Cell substance will break up and cell metabolismis disrupted.
This stage last for less than one week and if
continued leads to death.
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Time after eating
S o u r c e o f g l u c
o s e / e n e r g y
glycogen
gluconeogenesis, muscle
gluconeogenesis, other
fatty acid oxidation
food
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Time after eating
S o u r c e o f g l u c
o s e / e n e r g y
glycogen
gluconeogenesis, muscle
gluconeogenesis, other
fatty acid oxidation
food
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Time after eating
S o u r c e o f g l u c
o s e / e n e r g y
glycogen
gluconeogenesis, muscle
gluconeogenesis, other
fatty acid oxidation
food
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Time after eating
S o u r c e o f g l u c
o s e / e n e r g y
glycogen
gluconeogenesis, muscle
gluconeogenesis, other
fatty acid oxidation
food
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Intestine
Muscle
Liver
Brain
Kidney
Gluconeogenesis
Ketogenesis
Ureagenesis
Glutamine
Alanine / PyruvateGlucos
e
Ketones
Urea
NH3
Ketones
Glycerol
AGLFat
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Intestine
Muscle
Liver
Brain
Kidney
Gluconeogenesis
Ketogenesis
Ureagenesis
Glutamine
Alanine / PyruvateGlucos
e
Ketones
Urea
NH3
Ketones
Glycerol
AGL
Fat
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CARBOHYDRATE
FATS
PROTEIN
WATER
EFFECTS OF STARVATIONON
BASIC NUTRIENT'S
METABOLISM
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Hypoglycaemia
Depresses Insulin Increase Glucagonsecretion activity
Increases Gluconeogenesis Increase Glycogenolysis
Insulin/glucagon ratio decrease.
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Increase in activity of glucogenicenzymes like pyruvate carboxylase,
FDPase, glucose 6-P-ase that increaseboth gluconeogenesis and glycogenolysis.
Starvation decrease activity of enzymeG-6-PD, thus reducing HMP shunt andlipogenesis from carbohydrate.
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All this factors try tomaintain Blood sugar level asBrain and Red blood cellsrequire continuous supply of
Glucose in all condition.
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10
20
30
40
I II III IV V
Exogenous
Glycogen
Gluconeogenesis
G L U C O S E U T I L I Z
E D
( g / h o r a )
Ruderman NB. Annu Rev Med 1975;26:248
I II III IV V
GLUCOSEGLUCOSE GLUCOSEGLUCOSE,
KETONES
GLUCOSE,
KETONES
FUEL FOR
BRAIN
LEGEND
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Carbohydrate reserves are insufficient.
Fats of adipose tissue is largely
mobilised to the liver as FFA andoxidised for energy purposes.
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Starvation increase the activities ofthe ‘Hormone sensitive lipase’, so there
is increase in lipolysis in the adiposetissue.
Lipolysis release two components:Glycerol and FFA.
Glycerol acts as a substrate forGluconeogenesis and joins thecarbohydrate pool.
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FFA rise in the plasma from the veryfirst day of starvation and this rise isenhanced by muscular work, probablybecause of increased secretion ofcatecholamines from adrenal medulla
and sympathetic nerve ending.
As FFA level increase, ketogenesis is
stimulated and ketone bodies areformed.
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Vital organs like Brain and Heart canutilize ketone bodies during prolongedstarvation for survival.
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When fat stores are depleted andexhausted, proteins alone are availablefor energy purpose.
Tissue proteins are treated as ‘foodproteins’ , they are hydrolyzed to aminoacids to a larger extent.
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Released amino acids are utilized for themaintenance of the structural and functionalefficiency of vital organs.
Amino acids undergo de-amination in the liverand the non-nitrogenous part helps in the
maintenance of blood sugar level bygluconeogenesis.
Nitrogen excretion in urine is an index of tissue
protein consumption.
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During first few days, ECF is reduced due tostoppage of water intake and continuedobligatory losses.
On prolonged starvation,the ICF volume alsofall because of cellular breakdown while ECFshows a relative expansion due to the
subsequent shrinkage of cell mass that mayproduce oedema.
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Cellular disintegration cause loss ofintracellular potassium thus reducing
total body potassium.
The need for drinking water is reduced
after few days due to relativeexpansion of ECF.
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Mostly observed in animals, but some directobservation have been carried out onvolunteers and on professional fasting person.
During the first few days,craving for foods, at meal times.Later on this craving subsides
Desire for food vanishes.
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Weakness gradually increases. Strong dislike to undertake any physical
or mental effort. Subject falls into a state of
semiconsciousness.
Sleep increases and respirationbecomes slower. Body weight is steadily lost. The daily
loss in man during the first 10 days, isbetween 1 to 1.5% of the original bodyweight.
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Adipose tissue get thinned out andfinally disapper, visceral organs get
displaced.
Due to loss of subcutaneous fats skin
hangs loose with folds.
Vital organs lose the least weightwherease the less vital ones lose themost.
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Breaking the fast is harder thanfasting.
The longer the fast the more difficultit is to break correctly.
Start with fruits and raw vegetables insmall quantities and after three to fourdays gradually start your regular diet.
Avoid junk food for few days.
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When breaking from water fasting, go
to a juice fast for two days or eatfruits like oranges, mangos or pears.
In severe condition glucose is startedintravenously.
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Rest the digestive system Weight loss Allow for cleansing anddetoxification of the body
Promote greater mental clarity
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lead to a feeling of physicallightness, increasing energy level
From past to at present fasting hasbeen a catalyst to a number ofrevolution.
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Headache
Nausea
Muscle aches
Muscle cramps due to mineraldeficits such as sodium, potassium,calcium,magnesium, and phosphorus.
l d ld d l d
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Blood pressure could drop, leading tofainting spells especially when you tryto sit up or stand after lying down.
Uric acid levels may rise, causing severeattacks of gout or a uric acid kidney
stone.
Ventricular arrhythmias, experienced
usually during long water fasts.
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Deprivation of water along with foodfollows death in approximately 7 to 10
days time whereas food starvation in 3to 4 weeks or even longer depending onthe reserve of fats in the body.
Longest period of survival neverexceeds 9 to 10 weeks.
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CLINICAL
ASPECTS-
PROTEIN ENERGYMALNUTRITION
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The term protein energy malnutrition hasbeen adopted by WHO in 1976.
Highly prevalent in developing countriesamong <5 children; severe forms 1-10% &underweight 20-40%.
All children with PEM have micronutrientdeficiency.
It is most prevalent in South Asia and subsaharan africa.
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There are two varities of PEM1) Marasmus2) Kwashiorkor.
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The term derived from the Greek marasmos, which means wasting.
Inadequate intake of protein and calories and
is characterized by emaciation.
Represents the end result of starvationwhere both proteins and calories aredeficient.
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Severe wasting of muscle & s/c fats Severe growth retardation Child looks older than his age
Alert but miserable Hungry Diarrhoea & Dehydration
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Lack of physiological adaptation tounbalanced deficiency.
Body utilized proteins and conserve S/C fat.
Marasmus represents an adaptive responseto starvation, whereas kwashiorkorrepresents a maladaptive response tostarvation.
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Oedema
Psychomotor changes
Growth retardation
Muscle wasting
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Moon face
Hair changes
Skin depigmentation
Anaemia
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Hypoglycemia Hypothermia Hypokalemia
Hyponatremia Heart failure Dehydration & shock Infections (bacterial, viral & thrush)
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Guyton and Hall
Indian journal of Physiology.
Harpers textbook of Biochemistry.
Chatterjee-textbook of Biochemistry.
Journal of Biochemistry.