M.Prasad NaiduMSc Medical Biochemistry, Ph.D,.

Introduction Energy expenditure2 typesEnergy Expenditure in doing D2D activitiesEE in doing involuntary worksCalorific value of foodsBomb calorimeterUnit of Energy

Introduction Calorific value may be defined as the amount

of heat energy obtained by burning 1gm of the food stuff completely in the presence of O2

A calorie may be defined as the amount of heat required to raise the temp of 1gm of water by 10C

Average valuesCar – 4.1; Fats – 9.3; Pro-4.7

BMRThe rate of energy production under basal

conditions per unit time (1hr) and per sq.mt of body surface is known as BMR or

the amount of heat given out by a subject who though awake is lying a state of max.physical and mental rest under comfortable conditions of temp, pressure & humidity, 12-18hrs after meal (post absorptive state)

Basal conditionsPerson should awake but at complete rest

both physical and mentalPerson should be without food for atlease 12-

18hrs i.e., post absorptive statePerson should be in recumbent /reclining

position on bedPerson should remain in normal

environmental conditions like normal temp, humidity, pressure etc

Determination of BMR1. Open circuit method: both O2 consumption

and CO2 output are measuredRequires a high degree of tech skill and a

combussom apparatusLess rapid and more accurateTissot method and Douglous method 2. Closed circuit method: only O2 consumptionClinical practice (2-6 min under basal

conditions)Closed circuit systemBenedict-roth metobolism apparatus

Factors affecting BMR Age: children much higher than adults 6y65.5 12y50.4 20-30y 40 40-70y 38.5 to 35 Sex: women < males (females 5-17y more) Surface Area: α BMR ( Cal/Sq.m/hr) Climate: colder (high) tropical (low) State of Nutrition: BMR ↓ malnutrition, starvation Body Temp: BMR ↑10% with a rise in 10C Barometric pressure: rapid fall of O2 ↑ BMR Habits: Trained athlets & manual workers Drugs: Caffine, Benzidrine,epinephrine,alcohol ↑ BMR Anaesthetics ↓ BMR Hormones: thyroid, adrenal medulla, anterior pituitary ↑ BMR ! Mg thyroxine ↑ BMR by about 1000 cal Androgens 10% ↑ BMR Pregnancy: the BMR of pregnant mother after 6 months of gestation rises

Clinical aspectPathological variations in BMR: 1. Fever:2. Diseases: (Leukaemias 21-80%),

(Polycythemia 10-40%),(Cardiac failure / hypertension 28-80%)

3. Endocrine DiseasesDetermination of BMR is mainly used for

the assesment of thyroid functionIn Hyperthyroidism +75% or moreIn hypothyroidism -40% or more

Importance of BMRAs a diagnostic aidIn the calculation of caloric requirements of

an individual for prescribing a diet of adequate calorific value and planning nutrition for individuals or communities and populations at large

To note the effect of foods and drugs on BMR