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Anorexia and Hypermetabolism

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Anorexia and Hypermetabolism

What is Hypermetabolism?

Hypermetabolism is when the metabolic system is hyperactive so much that the person starts burning higher amounts of calories, leading to weight loss. 

Hypermetabolism or hypermetabolic conditions can occur in many different scenarios, particularly when the body needs to produce a lot of energy to heal itself. For example, when someone has suffered severe burns, multiple fractures, infection or sepsis, hyperthyroidism, traumatic brain injury, surgery, etc, the body will become hypermetabolic, burning a lot of calories to produce the energy necessary to heal. 

If the body is hypermetabolic and burning a lot of calories, the individual also has to consume a lot of calories - supply needs to match demand. 

When hypermetabolism occurs long term, it can cause insulin resistance, the breakdown of protein, carbohydrates, and triglycerides. Some of the serious symptoms that may also occur include:

  • anemia
  • elevated or irregular heart rate
  • shortness of breath
  • excessive weakness
  • muscle weakness and fatigue
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Hypermetabolism in Anorexia

When a person experiences prolonged starvation, such as in the case of anorexia nervosa (AN), hypermetabolism may occur. If the body has insufficient calories from food, it starts to break down fat and muscle in order to supply energy to sustain life. This is considered a hypermetabolic state because the body is continually trying to produce energy in spite of the lack of external caloric intake. As a result of this, patients begin to lose weight and can eventually become malnourished. 

When the body is in a hypermetabolic state and the individual begins treatment, medical supervision during the period of refeeding is very important. In extreme cases of prolonged starvation and hyper-metabolism, the body becomes depleted of many nutrients along with fats and proteins. If repeated too quickly, it can lead to electrolyte imbalances, nausea/vomiting, and even cardiac arrhythmias. Therefore, it is important to re-introduce food and calories slowly. It is especially important to work with a team of professionals that includes a dietitian, psychotherapist and medical doctor during this time of early treatment and refeeding. 

Here are some basic facts to know if you or a loved one are being treated for anorexia: (1)

  1. If calorie restriction has been mild or limited in duration, refeeding syndrome may not occur at all, and it may be totally safe to continue to encourage healthy eating at home while working with a therapist as an outpatient 
  2. If severe calorie restriction has occurred for a long time, a patient may need to spend some time in the hospital or in a medically-supervised program in order to be monitored during the refeeding period 
  3. Calories have to be increased slowly in steps. hypermetabolism may last three to six months after weight restoration.

If a person is exercising appropriately that is healthy. However, if a person is exercising excessively as one of the symptoms of their disease in order to keep off calories, bear in mind that heavy exercise also increases the hypermetabolic state, meaning that the individual will likely need even more calorie repletion in order to recover a healthy weight. Moderate healthy exercise is encouraged. Obsessive, compulsive and “compensatory exercise” is not. 

If you or a loved one is struggling with extreme calorie loss and experiencing a hypermetabolic state that may need medical treatment, reach out to your doctors. For help in treating eating disorders, call our team at Within Health.

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Treatment of Anorexia Nervosa
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Frequently asked questions


  1. Tetyana. (2015, September 7). Hypermetabolism in anorexia nervosa. Science of Eating Disorders. Retrieved May 19, 2022, from 
  2. Marzola, E., Nasser, J. A., Hashim, S. A., Shih, P.-an B., & Kaye, W. H. (2013). Nutritional rehabilitation in anorexia nervosa: Review of the literature and implications for treatment. BMC Psychiatry, 13(1).
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