What is the Harris-Benedict formula and how does it work for weight loss or performance?

Weight control is one of the traditional obsessions of cyclists due to its importance when it comes to achieving the best performance in climbs, where the important battles are fought in this sport, whether in a competition or in the usual challenge among friends during Sunday rides with the group. To know how much we should eat, it is necessary to first know how much we spend throughout the day. The Harris-Benedict formula comes to our aid.

The Harris-Benedict formula and your Basal Metabolic Rate (BMR)

In 1919, physiologists and nutritionists J. Arthur Harris and Francis G. Benedict, from the nutrition laboratory of the Carnegie Institute in Washington, published a study on basal metabolism. They had inferred, through an empirical method, a mathematical formula with which they were able to calculate the basal metabolism for a person with average muscle and fat.

The Basal Metabolic Rate or BMR determines the minimum calories a human being needs to maintain their vital functions. An amount of energy that the Harris-Benedict formula was able to calculate based on the individual's age, height, and body weight.

However, the original formula was created based on a typical individual with a certain amount of body fat and muscle mass, so when applied to individuals who deviated from this, for example, extremely thin or overweight individuals, the Harris-Benedict formula became quite inaccurate.

In 1984, doctors Roza and Shizgal reviewed the original study by Harris and Benedict, proposing some improvements to their formula which were incorporated by Pellet in 1990 in the article published in the American Journal of Clinical Nutrition where he reviewed the formulas to calculate the BMR, which are the ones used today.

How much you need to eat to perform or lose weight

When it comes to losing those extra pounds, a popular saying comes to our aid: what goes in must come out. That is, if we burn more calories than we consume, we will lose weight, otherwise we will gain it. In essence, it is as simple as that although with some caveats.

If we consume fewer calories than the BMR indicates, the body will enter a deficit and we will not have enough energy for our daily activities. If we excessively restrict our intake, we will lose weight, but the anxiety due to the feeling of hunger that will accompany us will probably lead us to give up and fall into the dreaded rebound effect by eating uncontrollably out of craving. Additionally, if besides losing weight we seek performance on the bike, it is necessary to have reserves that fuel our muscles during workouts.

That is why we must be very progressive when it comes to losing weight and restrict calories only slightly below our total daily expenditure. An expenditure that we can calculate with the data we obtain from our cycle computer regarding the energy consumption attributable to physical activity, and these devices are increasingly capable of obtaining this data more accurately and using the Harris-Benedict formula to calculate the Basal Metabolic Rate that will indicate the minimum calories we need to consume each day.

Harris-Benedict Calculator

After the various revisions and adjustments of the Harris-Benedict formula, these formulas are commonly used today to calculate the Basal Metabolic Rate or BMR.

• Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
• Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161

In addition, the data obtained from these formulas must be adjusted by a correction factor based on the individual's level of physical activity so that the calculation is even more precise. The different correction factors are:

• Little or no exercise: Daily calories = BMR x 1.2
• Light exercise (1-3 days a week): Daily calories = BMR x 1.375
• Moderate exercise (3-5 days a week): Daily calories = BMR x 1.55
• Intense exercise (6-7 days a week): Daily calories = BMR x 1.725
• Very intense exercise (twice a day, very intense workouts): Daily calories = BMR x 1.9

However, as we explained before, if we have the calorie consumption data from our cycle computer and complement it with the data provided by an activity tracker bracelet, we will have much more precision than using these correction factors because we will only have to add the daily activity expenditure to the BMR calculated by the formula.

That is why activity trackers have become an essential accessory for many professional cyclists that allows the team's nutritionists to adjust diets to the calorie intake so that the athlete can perform at their best while maintaining the lowest possible weight.