As I mentioned last week (click here if you missed it), weight is not a good indicator if you have RED-S. This is because a calorie deficit doesn’t always equal weight loss. You can be undereating and your weight can be stable. Read on to find out how this works.

Your body requires calories for more than just movement. Even if you were to lay in bed all day, you would still require calories. Many athletes forget that the body requires substantial calories even without exercise. These calories are required for various body processes such as pumping blood or digesting food. When not enough calories are consumed to cover both the calories expended through exercise and these everyday body processes, the body goes into “power saving mode.” The body reduces the calories expended through normal body processes in order to conserve energy. This can result in symptoms like constipation, feeling cold all the time, or poor circulation. This is the body trying to conserve energy because not enough calories are being consumed.

Using a laboratory test called “indirect calorimetry,” resting metabolic rate can be measured to determine if the body is in an energy conservation mode. Resting metabolic rate tells us how many calories that you are burning at complete rest. We can then calculate how many calories we would expect you to burn at rest based on your height, weight, age, and gender using an equation. If the calories you are burning through indirect calorimetry are lower than what we calculated it should be, this indicates that the body is conserving energy. For instance, if we calculated that an athlete should be burning 1500 calories per day at complete rest, but the indirect calorimetry test shows that the athlete is only burning 1400 calories per day at complete rest, this suggests that the body is in an energy conservation mode. As a result, this athlete could be undereating but not losing weight as the body has decreased the number of calories it requires.

The “calories consumed – calories burned = weight loss/gain” equation is flawed. It doesn’t consider how the calories consumed will impact the number of calories burned.  Athletes with RED-S often have a stable body weight despite being in an energy deficit. When not enough calories are consumed, the body goes into “power saving mode,” so that less energy is required.  This is one of the bodies finely tuned mechanisms to keep weight in a set range.

Categories: Megan Kuikman

Megan Kuikman

Hello! I’m Megan Kuikman. I’m a Registered Dietitian with specialized training in sports nutrition. My goal is to help athletes and active individuals achieve a healthy attitude towards health, training, and food. I empower athletes to fuel properly for training in order to restore their health and enhance performance. You can get in touch with me at:


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