Determining Daily Calorie Needs

Estimating daily calorie requirements is notoriously inaccurate. Even the very best calculators cannot determine the metabolic rate of an individual. Quite simply - everyone is different.

• Uses Mifflin-St Jeor formula (see below).


• Can also select old formula (Harris-Benedict), and a formula based on Lean Mass


• You can also choose BMR in the Exercise level. In this situation all weight loss calorie levels are blanked out.

The Best Guess

Calorie calculators will first estimate Basal Metabolic Rate (BMR). This is effectively the amount of energy expended per day. BMR is a measure of only the most basic functions (effectively the same as if you rested in bed the whole day). Other terms synonymous with BMR are Resting Metabolic Rate (RMR) and Resting Energy Expenditure (REE).

Once BMR has been estimated, various "activity" factors are applied. Once again these are best guesses. One individual may burn 100 calories on a 10 minute run - another individual may burn 150 calories.

Mifflin - St Jeor Formula

The Calorie Needs Calculator currently uses the formula proposed by MD Mifflin and ST St Jeor1.

Why This Formula?

As recent as 2005, the ADA (American Dietetic Association) published a comparison of various equations2. The Mifflin-St Jeor was found to be the most accurate.

Men

10 x weight (kg) + 6.25 x height (cm) - 5 x age (y) + 5


Women

10 x weight (kg) + 6.25 x height (cm) - 5 x age (y) - 161.

Lean Mass Formula

This can be selected on the calculator. It is a variation1 on the basic Mifflin-St Jeor equation that will base the equation on Fat Free Mass (FFM) or Lean Mass. This is more accurate for those who are leaner (and who know their body fat percentage!).

Men & Women

19.7 * Fat Free Mass + 413



Where Fat Free Mass = Weight - (Body Fat Percentage * Weight).

Harris-Benedict Formula

This formula was created in 1919, and due to changing lifestyles, it tends to overstate calorie needs by 5%. The results tend to be skewed towards both obese and young people3.

Men

66.5 + (13.75 X weight in kg) + (5.003 X height in cm) - (6.775 X age in years)

Women

655.1 + (9.563 X weight in kg) + (1.85 X height in cm) - (4.676 X age in years)