How energy expenditure can be measured by factorial method?

Assessment of energy expenditure:

Energy expenditure can be measured through different methods and some of then are described below:

Factorial method:

Individual component of total energy expenditure (TEF) are measured separately and subsequently summed to calculate total energy requirements of individuals. Following are the components of TEF

Basal metabolic rate(BMR)

Thermic effect of food

Physical activity

TEE is the energy expenditure of human body during steady state of health. It is the sum of BMR , energy expenditure attributed to physical activity and TEF. It can be represented following formula;

TEF=BMR60.70%+Physical activity 20.30%+Thermic effect of food 10%

Basal metabolic rate(BMR)

BMR is the minimal calories required to maintain basic physiological function of the body (breathing, thermoregulation, heart beating etc.) when a complete rest. It is typically measure during deep sleep at night or early morning hours.

Infant and younger children have BMR relatively higher when compared to adults owing to their rapid growth and development.

Muscle mass of men in more as compared to women, thus have higher BMR. Similarly, muscle mass in older adults tends to decline, the BMR also decrease. BMR is influenced by age, gender, body composition, body size , growth period, climate and body temperature.

Resting metabolic rate (BMR) on the other hand is the rate of energy expenditure when at rest. It is generally measured after 8-12 hour of fast followed by 30 minute of rest. Moreover, it is relatively easier and less stringent in measure.

It may overestimate the energy requirement, by approximately 3-10% when compared to BMR. The temperature environment ( 68-82F vs 82-86F).

TEF slightly temperature increase between 2-5% . Under most circumstance, body temperature can be regulated by clothing etc. However, the inherent mechanism in mammals aimed to regulate body temperature within narrow limits is called as thermoregulation.

Through people can adapt to the ambient temperature variations have slight contribution towards total energy expenditure.

In cold stress environment , RMR may increase up to 2.5 fold due to shivering mechanism.

General formula for calculating RMR:

For men:

(1kcal )multiply by ( kg body weight) multiply by ( 24 hours )

For women:

(0.9 kcal) multiply by ( kg body weight ) multiply by ( 24 hours )

b. Physical activity level/

According to WHO definition physical activity is any bodily movement produced by skeletal muscles that require energy expenditure-including activities undertaken while working, playing, carrying out household chores, travelling and engaging in recreational pursuits.

The estimated total energy requirement of a person can be calculated by multiplying BMR with appropriate factor corresponding to the activity undertaken known as physical activity level PAL.

Energy expenditure= BMR multiply by PAL

Total physical activity is the sum of household chores, leisure time activity, care giving, travelling, sports and occupational activity.

Physical activity level in both gender

ate	Women	Men
Very low level: physical activity during work or leisure time	1.4	1.4
Moderately itense	1.6	1.7

Calories burnt in 30 minutes of physical activity

Physical activity	Kcal burnt in minutes	Physical activity	Kcal burnt in minutes
Ironing	69	Lawn walking(using power mover)	165
Dusting and cleaning	75	Riding bicycle	180
Walking	99	Aerobic	195
Vacuum cleaning	105	Swimming(slow crawl)	195
Playing golf	129	Playing tennis(singles)	240
Playing tennis(double)	150	Running (@1o minutes/mile)	300
Brisk walking	150	Running (@8.5 minutes/mile)	345

Physical activity recommendations:

According to WHO guidelines adults aging 18-64 should do minimum 150 min of moderately intense exercise during the week for health living. Moreover, muscle-strengthening activities are recommended on 2 or more days of a week. Moderately intense exercise is the level of activity .

Thermic effect of food TEF:

TEF is also termed as dietary-induced thermogenesis. It is defined as the energy used for digestion, absorption, transport, metabolize and disposal of ingested nutrient from food.

Thermic effect of macronutrients

Nutrient	Thermic effect(%of totle kcal)
Carbohydrate	5-10
Protein	20-30
Fat	0-5
Mixed diet 10

Prediction equation

Different equation are used predict energy requirement of individual by accounting their, age, gender, height, and weight.

a)Estimation of RMR

RMR is linearly correlated with fat-free mass and can be calculated from body size(weight, height), age and gender using predictive equations. these equations are useful for RMR prediction of individuals through indirect calorimetry.

Mifflin-St jeor Equations

Males;

RMR= (9.99multiply weight in Kg)+(6.25 multiply height in cm)+(4.92 multiply age)+5

Females;

RMR =(9.99 multiply weight in Kg)+(6.25 multiply in cm)+(4.92 multiply age)-161

Harris- Benedict Equation

Males;

BMR= 66.5+(13.75 multiply in Kg)+(5.0 multiply height in cm)-(6.76 multiply age)

Females;

BMR= 65.1+(9.56 multiply weight in Kg)+(1.85 multiply height in cm)-(4.68 multiply age )

Mifflin - St jeor;

The equation was developed from normal weight,

Overweight, and obese individuals in 1990

During validation, it has correctly predicted RMR( +10%) in:

82% of the normal weight individuals

70% of the obese individuals

Overestimate and under estimate are equally common for normal and

obese individuals

Formula does not work well for elder(>80y)

Harris- benedict

It was developed primarily from normal weight white normal weight

white men and women during studies

conducted from 1907 to 1917

During validation, it has correctly predicted RMR (+%) in:

45%-80% of the normal weight individuals

36%-64% of the obese individuals

Overestimates of RMR are more common than underestimates for normal and obese individuals

Formula does not work well for elder(>80y)

Factor for PA level;

PA level Male Female