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Foundational Techniques For Dietetics Calculations

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Do you also find it difficult to solve basic dietetics calculations’ including Body Mass Index (BMI), Ideal Body Weight (IBW), Fluid Requirement (FR), Basal Energy Expenditure (BEE) and Total Energy Expenditure (TEE)? I have some good news for you so don’t worry anymore. In this article I will tell you the fundamental techniques to solve these calculations smoothly and ace your exams. Let’s begin!

  1.       BMI

You might wonder what is BMI? Don’t worry I got you covered.

Body mass index, or BMI, is a ratio of weight to height. It’s an accurate approach to determine whether a person’s weight is balanced with his/her height.

FORMULA:    BMI= Weight (in kg) / Height (in m2)

let’s take an example here:

Example: Shabnam is a university student having weight 65kg and height 5 feet 3 inches. What would be her BMI?

Data available:

Weight = 65kg

 Height = 5’3”

BMI =?

SOLUTION:

                                   BMI= W (in kg)/H (in m2).

Firstly, we will convert height in feet to height in meter2. For that multiply feet given with 12 and then add the additional inches. After this multiply the total inches with 0.0254 and you will get your answer in meter. Now you have to take square of the height in meter and you will get m2.

Height= (5×12) + 3 = 63 inches

H=63×0.0254 =1.60m

H= 1.60×1.60 = 2.56m2

Now put the values in given formula.

 BMI= 65/2.56

                                      BMI= 25 kg/m2 

To save time, you can find BMI with our online BMI Calculator: https://sehatnutrition.org/bmi-calculator/ 

  1. IBW

Ideal body weight, or IBW, is thought to be the healthiest weight for an individual, based mostly on height but adjusted by elements including gender, age, build, and level of muscle development. For men, ideal body weight is calculated by using 106 pounds for the first 5 feet of height and adding 6 additional pounds for each inch. Women ideal body weight calculation starts with 100 pounds for the first 5 feet of height, and you only add 5 pounds for each additional inch. We will learn the calculations for both genders one by one.

FORMULA:

(For a male) 106lbs for first 5 feet and 6lbs for additional inches.

(For a female) 100lbs for first 5 feet and 5lbs for additional inches.

  1. IBW FOR MALE

Example: Hamid is a diploma student and his height is 5 feet 9 inches. What would be his IBW?

Data available:

Height=5’9”

IBW=?

Solution:

IBW = 106lb + 6lb (inches over 5 feet)

IBW= 106 lb. + 6lb (9”)

Multiply 6 with 9 inches,

IBW= 106lb + 54lb

Now add the lbs.

IBW= 160lb

To convert it into kg divide by 2.2:

IBW= 160/2.2 =72.7kg

 

  1. IBW FOR FEMALE

Example: Saima works in a hotel as a receptionist and her height is 5 feet 3 inches. What would be her IBW?

Data available:

Height=5’3”

IBW=?

Solution:

IBW = 100lb + 5lb (inches over 5’)

IBW= 100 lb + 5lb (3”)

Multiply 5 with 3 inches,

IBW= 100lb + 15lb

Now add the lbs.

IBW= 115lb

To convert it into kg divide by 2.2:

IBW= 115/2.2 =52.2kg

To save time, you can find BMI with our online BMI Calculator: https://sehatnutrition.org/ideal-weight-calculator/

  1.   Fluid requirement

Why calculating fluid requirement is necessary in nutrition?

BECAUSE! A vital component of life and health, water is involved in almost every process of the human body. The amount of fluid that each person needs is determined by their weight and varies with each individual. People are advised to follow the reference values of the fluid need in order to maintain the proper balance between water intake and water losses.

FORMULA: First 20kg 1500 ml & for each additional kg add 25 ml.

Example: A college student wants to know her daily fluid requirement, her weight is 65kg. What would be her FR?

Data available:

Weight= 65 kg

Solution:

1500ml for the first 20kg and 25ml for each additional kg.

Fluid requirement= 1500ml + (25×45) ml

Fluid requirement= 1500ml + 1125ml

Fluid requirement= 2625ml

Conversion:

1 glass (1cup) = 250 ml

e.g. if one’s fluid requirement is 2000 ml, it can be calculated as 2000 ÷ 250 = 8 (means 8 glasses).

However, in this case:

Fluid requirement= 2625/250ml

  Fluid requirement= 11 glass /day

 

CALCULATION OF ENERGY REQUIREMENTS

Method: USING HARRIS BENEDICT EQUATION:

Total Energy Requirement = BEE x Activity Factor x Injury factor

 

Step  I:
 Calculate BEE (Basal Energy Expenditure) or BMR (Basal Metabolic Rate): Energy expended on basic body functions needed to sustain life.

BMR for female = 655 + (9.6× weight in kilos) + (1.8 ×height in cm) – (4.7 × age in years)

BMR for male = 66 + (13.7 × weight in kilos) + (5 X height in cm) – (6.8 × age in years)

Conversions: 

Weight in kg = weight in lbs/2.2  

Height in cm =height in inches x 2.54

Step II:

Multiply BMR by the appropriate activity factor, as follows:

  • Sedentary(little or no exercise): BMR x 1-1.2
  • Lightly active(light exercise/sports 1-3 days/week): BMR x 1.1- 1.375
  • Moderately active(moderate exercise/sports 3-5 days/week): BMR x 1.55
  • Very active(hard exercise/sports 6-7 days a week): BMR x 1.725
  • Extra active(very hard exercise/sports & physical job): BMR x 1.9

Step III:

Multiply by injury factor.

  • Surgery: Minor = 1.0 – 1.1 Major = 1.3 – 1.9
  • Infection: Mild = 1.0 – 1.2 Moderate = 1.2 -1.5 Severe = 1.4 -1.8
  • Trauma: Skeletal = 1.2 – 1.35 Blunt = 1.15 – 1.35
  • Burns: severe thermal= 2.1
  • Sepsis: 5 – 2.0
  • Cancers: 0 – 1.5
  • COPD, malnourished: 3

 

STEP 1: BEE

BEE, the most imperative part of Dietetics calculation which you would not want to neglect! So, let’s see what is it?

The quantity of energy, expressed in kcal/day or kj/day, that should be required to support all body functions and movements for an organism to exist for a day is known as basal energy expenditure (BEE). BEE may be computed using the Harris-Benedict basal energy expenditure formulae. The BEE may make up 40–70% of overall energy expenditure, depending on the level of physical activity. We will learn the calculations for both genders one by one.

  1. ENERGY REQUIREMENTS FOR FEMALE

Example: Javeria is 21 years old first year medical student. Her weight is 65kg, and height is 5’3”. She has a sedentary lifestyle and don’t have any injury at present. Calculate her Total Energy Expenditure.

Data available:

WT= 65KG

HT= 5’3”

AGE= 21yrs

Physical activity= Sedentary

Injury factor= none

SOLUTION:

first, we will Convert height in “cm”

HT=5’3” =5×12+3=63”

HT=63” × 2.54= 160 cm

now we will calculate BEE:

BEE=655.1+ {9.6×WT (kg)} + {1.85×HT (cm)}-{4.7×Age(years)}

BEE=655.1+{9.6×65kg} + {1.85×160cm}-{4.7×21years}

BEE= 655.1+624+296- 98.7

BEE= 1476.4 kcals

STEP 2: TEE

How can we forget TEE!

Calories burned throughout the course of a 24-hour period are measured as total energy expenditure (TEE). These calories are produced by the body as it works to maintain its own survival, including all physical activity as well as cognitive and digestive processes like breathing and digesting.

FORMULA: TEE=BEE × PHYSICAL ACTIVITY × INJURY FACTOR

put values:

TEE=1476.4 × 1.1 × 1                                

 TEE=1624.04 kcals 

  1. ENERGY REQUIREMENTS FOR MALE

STEP 1: BEE

Example: Ahmad is 45 years old accountant. His weight is 87kg, and height is 5’9”. She has a slightly active lifestyle and don’t have any injury at present. Calculate his Total Energy Expenditure.

Data available:

Weight = 87kg

Age = 45yrs

Height = 5’9”

Physical activity = 1.1 (slightly active)

I.F= none

SOLUTION:

first, we will Convert height in “cm”

HT=5’9” =5×12+4=69”

HT=69” × 2.54= 175.26 cm

BEE=66.5+ {13.7×WT (kg)} + {5×HT (cm)}-{6.8×Age(years)}

BEE=66.5+ {13.7×87 (kg)} + {5×175.26 (cm)}-{6.8×45(years)}

BEE= 66.5+1191.9+876.3-306

BEE= 1828.7 kcals

STEP 2: TEE

FORMULA: TEE=BEE × PHYSICAL ACTIVITY × INJURY FACTOR 

TEE=1828.7 × 1.1 × 1

TEE= 2011.5 kcals

 

The above-mentioned calculations with their purposes will assist you both academically and for customizing Diet plans. Therefore, always keep in mind PRACTICE MAKES PERFECT And never stop practicing. BEST OF LUCK!

Dn.Misbah Saher is a top student of Diet and Nutrition at University of Lahore. She is also a freelance nutritionist and Blog-writer, keen in spreading awareness about Diet and Health related issues. She can be reached at @dietitians_corner.

Disclaimer: The information in this article is not intended as sound medical advice for your particular illness; rather, it is meant to increase awareness of common health issues. Before implementing any recommendations made in this article or choosing a treatment plan based on its contents, you should always speak with a qualified healthcare professional.

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