metabolism 3 - copy

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Factors affecting

the

Lecture 2

Metabol ic rate


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Sympatheticstimulation

Factors

affecting themetabolic rate

MuscularexerciseSleep

Emotional state

alnutrition and

starvation

Environmental

temperature

Recentingestion of

food

age and sexHormones

Fever


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10-20 foldsBMR


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Oxygen Debt

Sprinters continue to breathe more deeply and rapidly for a number of

minutes at the end of their race. This will enable them to pay back the

oxygen debt.


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increased sympathetic nervous system activity following foodintake.

Specific dynamic action of food

Definition: The SDA of food is the obligatoryenergy expenditure that occurs during assimilation ofFood into the body.

The SDA of carbohydrates may be a manifestation of the extra-

energy required to form glycogen.

The SDA of fats may be due to a direct stimulation of metabolismby the liberated fatty acids.

The SDA of proteins may be due to deamination of amino acids inthe liver or from a stimulatory effect of some amino acids on

cellular chemical processes.


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Factors affecting the SDA of food


Amount of food:

Type of food: An amount of proteins sufficient to provide 100Kcal increases the metabolic rate of a total of 30 Kcal.

A similar amount of carbohydrate increases it 6 Kcal

A similar amount of fat 4 Kcal.


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Example

if the daily energy requirement of an individual is 3000 Kcal andthis amount is supplied by proteins only, the metabolic rate

would increase by 900 Kcal (3000 x 30/100) .So, the energyoutput will be 3900Kcal and not 3000Kcal. This excess heat isderived from the energy stores of the body


PROTEINS


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Environmental

temperature

U


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Fever1 degree

14%


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Sympatheticstimulation

(calorigenic)


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Sleep(15%)


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Age and sex


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Hormones


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Malnutritionand

starvation


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Emotionalstate


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Pregnancyand lactation


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Height,weight and

surface area


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THE BASAL METABOLICRATE

Definition of BMR:

It is the minimal energyexpenditure for the body toexist. It results from theinherent activity of thetissues (activity of thecentral nervous system,heart, kidneys, liver, .),without the effect ofexercise or external

factors .


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It is the rate of energy output,measured under the followingbasal conditions:

Complete physical and mental

rest. (but not asleep)

Post absorptive state

At a comfortable roomtemperature


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It accounts for about 50 to70 per cent of the dailyenergy expenditure in most

sedentary individuals.


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Value of BMR:

For a normal adult male about40 Kcal/h/m2 It is usually expressed as apercentage of increase or

decrease above or below thenormal standard value for ageand sex. Normally the BMR is 15% of

the normal standard value.


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The basal metabolic ratediffers according to:

age.

sexbody surface area


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Factors affecting the basalmetabolic rate:They are those affecting themetabolic rate in general

except the effect of exercise,food ingestion, environmentaltemperature, sleep andemotional status because the

BMR is measured under basalconditions

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