80/20 Nutrition Planner

There are many ways to calculate energy requirements for weight loss based on age, sex and physical activity level. All these methods contain inherent errors.

For Weight Loss

A very simple calculation may be used to estimate energy requirements:

For:

Weight Loss: 20-25kcal/kg of body weight (85-105KJ/kg of body weight)

Weight Maintenance: 25-30kcal/kg of body weight (105-125KJ/kg of body weight)

Use the lower end of the range for those who are not very active. Use the upper end of the range for males, and those who tend to be more active.

For Weight Gain

The following is a simple method to estimate energy requirements for weight gain:

Energy requirement for weight gain = 35kcal/kg of body weight (145KJ/kg)

For those who are very physically active, you may want to increase the energy requirement by 500-1000KJ (120-240Kcal).

Energy calculator for weight loss / weight maintenance / weight gain

Alternative Method for Estimating Energy Requirement

(can be used for more physically active individuals)

Adapted from Truswell AS (ed). Recommended Nutrient Intakes, Australian Papers. Australian Professional Publications, Australia, 1990.

Because an accurate measure of energy expenditure is difficult to obtain, you can calculate proposed energy requirement following the guidelines suggested in the reference. However, it must be recognised that estimates of food energy requirements obtained by this method are only approximate, especially for individuals in whom variations in energy requirements can be very large, even for persons of the same age, sex and body weight and apparently similar level of activity.

Firstly, determine basal metabolic rate (BMR) using the predictive equations in Table 1. This is the minimal amount of energy needed to keep an awake, resting body alive. BMR includes the energy you need for all your essential metabolic functions, but does not include any energy for any physical activity (ie. even as little as brushing your teeth) or the digestion and absorption of food.

Secondly, determine approximate level of activity (expressed as a multiple of the BMR) from the values listed in Table 2.

Thirdly, determine daily energy expenditure by multiplying BMR that you calculated above by your estimated level of activity. This is expressed as a multiple of BMR because bigger people require more energy to do exactly the same physical activity as smaller people - this is simply because they have more weight to move around.

Add on to the estimate of energy expenditure any extra energy requirements for growth, pregnancy or lactation as appropriate. The energy cost of growth may be taken as 8kJ/kg body weight for children aged 10-14 years, 4kJ/kg at 15 years, and 2kJ/kg at age 16-18 years. The energy cost of pregnancy may be taken as 0.85-1.1 MJ/day assuming activity does not change. The energy cost of lactation may be taken as 2.0-2.4 MJ/day.

Correct the estimate of energy requirement obtained from 4 above for the metabolisable energy content of the diet to be eaten, if appropriate. For the "typical" Australian diet which contains about 20g/day of dietary fibre no correction is necessary. For high fibre diets (>40-50g) the estimate of energy requirement should be increased by about 5%.

Table 1: Equations for estimating basal metabolic rate (BMR) in MJ/day from body weight (kg) in adults and children over the age of 10 years (body weight in kg). To convert to calories divide KJ by 4.18.

From Schofield WN, Schofield C, James WPT. Basal metabolic rate - Review and prediction, together with an annotated bibliography of source material. Hum Nutr Clin Nutr 1985;39C:1-9

Table 2: Average daily energy expenditure of adults and children over the age of 10 years at different levels of activity expressed as multiples of basal metabolic rate (BMR).

NB. Most people in the population would probably be classified as Light or Light-Moderate.

Alternative Method Energy calculator