By Sarah-Ashley Robbins, MD
Hypermetabolism is a phenomenon seen during the journey towards recovery from anorexia nervosa. When a person is actively restricting calories, the metabolism becomes very slow. With very little food coming in, the body is already having to ration available energy towards life sustaining functions like pumping the heart, breathing, consciousness, movement, etc. The body is in energy conservation/hibernation mode at this point, doing everything in its power to keep the body alive in the face of starvation. When a person takes steps toward recovery and weight restoration, they will start increasing the calories they consume. In response to this, the metabolism will start to speed up to capture this new source of energy. During this process there is often a period of hypermetabolism, where the metabolism becomes very fast. The reason this happens is not well understood, but this is seen almost universally in the weight restoration process. Often people are shocked with how much they must eat to maintain or even gain a minimal amount of weight! Someone who was subsisting on a very low number of calories a day before undergoing weight restoration may need more than 4-5 times the calories per day to make up for this hypermetabolism. This hypermetabolic state can last a few weeks and gaining even the smallest bit of weight is challenging. Some individuals may even begin to lose weight initially. The amount of daily intake needed can be incredibly distressing to the eating disorder voice. This process is not intuitive and following the body’s intuition during this process can actually be harmful. This is why it’s so important to have a knowledgeable and trustworthy multidisciplinary team including a dietitian, therapist, and medical provider when beginning this process.
I also want to recognize that every body is different during this process. Lots of individuals who significantly restrict calories may live in what society deems a “normal” or “larger” size body. Their genetics are designed to aggressively protect their body weight so that they lose only small amounts or no weight in response. We can’t always rely on weight to tell us how much a body needs to be adequately nourished. Regardless of body size, any person who restricts calories for a prolonged period then starts to refuel their body may experience hypermetabolism. In some cases, weight actually increases because the body is storing more to be better prepared for the next period of starvation. How the body reacts to hypermetabolism is all up to an individual’s genetics. This can be incredibly triggering to the eating disorder voice. Society and many doctors may tell the individual that something must be wrong with them. Some people may even recommend the very thing the body doesn’t need, to restrict calories again! There are so many factors that go into this process; close monitoring is required for successful recovery. An individualized plan is needed to make sure someone is getting adequate nutrition to support their body’s daily needs and activity levels, regardless of body size.