The Harris-Benedict Equation is one of many predictive formulas designed to calculate the basal metabolic rate of a person based on certain characteristics such as sex at birth, weight, height, and age. The basal metabolic rate is the rate of energy expenditure by a person at rest. In other words, it tells us how much energy in kilocalories a body needs per day simply to perform basic life-sustaining functions, and eliminates any consideration of the variable of physical activity. Your BMR accounts for approximately 60% of your energy requirements per day.

Of the many formulas for predicting BMR, three have become most prominent: the Harris-Benedict, the Mifflin-St. Jeor, and the WHO/FAU/UNU equations. Each has its own flaws and either overpredicts or underpredicts BMR in certain demographics. However, the most accurate of the three for the broadest market (above age 18 and under age 70), when combined with a physical activity variable to include the obese and the very lean, is the Harris Benedict Equation.

This is the formula Seymour uses to calculate optimal kilocalorie intake for each of our users. Importantly, we also ensure that the calories we provide are nutritionally dense and focus area appropriate. Thus we speak of nutrition tracking rather than simple calorie counting.

J. Arthur Harris and Francis G. Benedict first posited their equation in 1918. It has been updated twice since then, however, the consistent accuracy of the equation over time, even in the context of changing lifestyles, speaks to the remarkable achievement of these scientists.

The gold standard (and clinical reference standard) for assessing energy requirement is indirect calorimetry, but this is not widely available and is inappropriate when offering meals to a wide population.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1091498/

https://www.jsams.org/article/S1440-2440(11)00041-7/fulltext

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6157446/

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