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Simon Oppowa edited this page Sep 18, 2023 · 2 revisions

Calculations

This wiki page describes important internal calculations within the OpenNutriTracker application. It is there to help you understand how things like the daily calorie target and macronutrient distribution are calculated.

Table of Contents

  1. Introduction
  2. Total Daily Energy Expenditure (TDEE)
  3. Metabolic equivalent of task (MET)
  4. Macronutrients Distribution
  5. Body Mass Index (BMI)

Introduction

Internal calculations are based on recommendations from scientific institutions such as the World Health Organization (WHO) or the Institute of Medicine (IOM).

Total Daily Energy Expenditure (TDEE)

The equation for energy intake is based on the concept of TDEE, which is the amount of energy an individual uses in a day. (The app adds all calories used by workouts seperately) To calculate TDEE, the application uses the "Institute of Medicine (IOM) equation". The IOM equation for estimating energy expenditure varies based on age, gender, weight, height, and physical activity level. Below is a generalized representation of the equations:

  • Men: Cal/day = 662 - (9.53 × age in years) + PA × [(15.91 × weight in kg) + (539.6 × height in m)]

  • Women: Cal/day = 354 - (6.91 × age in years) + PA × [(9.36 × weight in kg) + (726 × height in m)]

Where PA (Physical Activity coefficient) is:

  • Sedentary: 1.0
  • Low Active: 1.12
  • Active: 1.27
  • Very Active: 1.45

Metabolic equivalent of task (MET)

The Metabolic Equivalent of Task (MET) is a unit of measurement that quantifies the energy expenditure of a specific physical activity. It serves as a simple, convenient way to compare the energy costs of various activities relative to a baseline, usually the energy expenditure of sitting quietly. One MET is defined as the amount of oxygen consumed while sitting at rest, which is roughly equivalent to 3.5 milliliters of oxygen per kilogram of body weight per minute ( ml/kg/min ml/kg/min).

The MET values from different activites were taken from the Compendium of Physical Activities

Macronutrients Distribution

Macronutrients are the primary nutrients that provide the energy necessary for the body to function. The three main types of macronutrients are carbohydrates, proteins, and fats. Each has its own unique role in the body and provides a different amount of energy per gram:

The macronutrient goal is calculated based on current calorie goal:

  • Carbohydrates: Provide 4 calories per gram and are the body's primary source of energy. (60 % of calorie goal)
  • Proteins: Provide 4 calories per gram and are essential for growth, repair, and maintaining body tissues. (15 % of calorie goal)
  • Fats: Provide 9 calories per gram, making them the most energy-dense of the macronutrients. (25 % of calorie goal)

Body Mass Index (BMI)

The Body Mass Index (BMI) is a numerical value calculated from an individual's height and weight. It is widely used as a screening tool to categorize individuals into different weight categories, such as underweight, normal weight, overweight, and obese. The formula for calculating BMI is:

BMI = Weight(kg) / Height (m)²

The World Health Organization (WHO) has established the following BMI categories:

  • Underweight: BMI less than 18.5
  • Normal weight: BMI 18.5–24.9
  • Overweight: BMI 25–29.9
  • Obesity I: BMI 30–34.9
  • Obesity II: BMI 35–39.9
  • Obesity III: BMI 40 or higher
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