Hypermetabolism in Eating Disorder Recovery: What It Is, Why It Happens, and What to Do

Many people in eating disorder recovery notice something unpleasant: they begin eating more consistently, yet their body asks for even more. This can feel confusing, even for the dietitian on the case! As you may imagine, struggling to eat enough in general and then being told it’s not enough may be unsettling for an eating disorder patient in the early stages of recovery. It can even bring up fears about whether recovery is “working” or “worth it.”

In reality, this experience is often linked to hypermetabolism, a well-documented physiological process where the body increases energy expenditure during renourishment and recovery to support tissue repair, restoration of organ function, and healing from prior energy deficiency (aka intentional or unintentional restriction).

As eating disorder dietitians, we see every day that nutrition is far more complex than a simple “calories in, calories out” equation. While short-term changes in intake can influence weight, the body is not a static system. It adapts! The human body is highly responsive in ways designed to protect survival, especially in response to not having enough food.

When we think about the pursuit of weight loss, science shows that long-term weight loss beyond 5 years can be difficult to come by (Hay et al., 2014). One reason for this is that metabolism adapts- when someone undereats, for any reason, we know that the body adapts and metabolism slows to conserve energy. More on this in another post, and we highly recommend reading the book Sick Enough by Dr. Jennifer Gaudiani for a deeper dive.

On the flipside, when someone starts to eat more after a period of restriction, metabolism kicks back into gear. The body finally has energy coming in again, so it starts to invest! This can present as hypermetabolism AKA needing more calories than previous baseline to function, and even more to gain weight.

For some clients experiencing hypermetabolism it can feel frustrating to commit to recovery, follow a meal plan, and still feel hungry all the time and/or not see the scale go up if weight restoration is expected to be part of that person's journey. This can be distressing, but it’s not a sign that anything is broken. After periods of restriction, the body may increase metabolic rate significantly. In some cases, individuals may require substantially higher energy intake during recovery to support healing processes.

Research and clinical experience show that factors like genetics, duration of restriction, and medical history all influence how the body responds (The Gaudiani Clinic, 2018). It’s also important to be clear here: diet culture often frames certain metabolic responses as “better” than others. But struggling to gain weight is not morally superior to struggling with weight loss resistance as a metabolic response. Both are physiological responses, neither reflects willpower, worth, or health on its own.

Okay, so what is hypermetabolism really?

To summarize, hypermetabolism is when your body uses more energy than usual as it works to heal, restore, and repair after a period of:

• Engaging in restrictive eating disorder behaviors

• Chronic dieting

• Significant weight loss

• Overexercise

• Illness, injury, or medical stress

• Malnutrition, even if it wasn’t caused by an eating disorder

• Or often, a combination of any of the above!

After periods of malnutrition, the body often has to do more than simply “maintain” basic homeostasis. It may be working to restore organ function, repair muscle tissue, rebuild bone and connective tissue, restore digestive & hormonal function, and even resume growth in adolescents. In this rehabilitation phase, the body is not just eating for the present, but also the past! This phase can include signs of hypermetabolism such as feeling hungry soon after eating, needing more food than expected to be satisfied, waking up hungry at night, feeling clammy or sweaty, increased heart rate, and/or fatigue despite increased food intake. Some folks describe feeling like their body is “burning through” food as they’ve never experienced before. While not all cases of hypermetabolism are the same, increased hunger and energy needs are fairly common.

Additionally, people recovering from hypermetabolism may experience extreme hunger signals and constant thoughts about food. If your body is in hypermetabolism, increased hunger and difficulty maintaining weight are only two of many possible symptoms. Tachycardia, fatigue, sweating, and preoccupation with food may be present as well.

Key things to understand about periods of hypermetabolism:

• This is your body doing exactly what it’s designed to do: SURVIVE!

• It can feel uncomfortable to have exact answers or a timeline.

• Your team will closely monitor your body’s response to changes in intake via the scale and assessment of symptoms like fatigue, dizziness, iron-deficiency anemia, tachycardia, & more.

  
  

Importantly, hypermetabolism may occur in people of all body sizes. Anyone can restrict their intake for an extended period of time, therefore anyone can have a hypermetabolic response.

How long hypermetabolism lasts depends greatly on factors like the length and intensity of food restriction, age, medical status, consistency of nourishment, stress, sleep, genetics, and movement. Dr. Gaudiani states, "How the body reacts to hypermetabolism is all up to an individual’s genetics” (The Gaudiani Clinic, 2018). This period could last weeks, maybe even months for some. Remember, your body will not be this way forever. The body often settles once it realizes that the famine is over and trusts that nourishment is consistently available. The most important things you can do are honor the hunger, follow your meal plan if you have one from your dietitian, and trust the process.

Hypermetabolism can feel intense and frightening, but it is often a sign that the body is doing exactly what it was designed to do: protect, repair, and heal. Your hunger is not the problem. It likely will be a part of the solution.

If this sounds familiar, you don’t have to figure it out alone. Seeking help from an eating disorder-specialized dietitian, doctor, and/or therapist is a great place to start.

Thanks for reading, and reach out to us if you are needing support during this tricky spot of recovery. We offer a free discovery call if you'd like to chat to see if our practice is the right fit, and to answer any and all questions you have about working together. Not sure if we can work with you in your state? Reach out and we will be happy to check!

Citations

Hay, P., Chinn, D., Forbes, D., Madden, S., Newton, R., Sugenor, L., Touyz, S., & Ward, W. (2014). Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for the treatment of eating disorders. Australian & New Zealand Journal of Psychiatry, 48(11), 977–1008. https://pmc.ncbi.nlm.nih.gov/articles/PMC5764193/

Monte Nido. (n.d.). Anorexia and hypermetabolism: What to expect during recovery. https://www.montenido.com/blog/anorexia-and-hypermetabolism-what-to-expect-during-recovery

National Center for Biotechnology Information. (2018). Hypermetabolism and medical complications during refeeding in anorexia nervosa. Nutrition in Clinical Practice. https://pmc.ncbi.nlm.nih.gov/articles/PMC5968865/

National Center for Biotechnology Information. (2024). Medical complications and management of atypical anorexia nervosa. Journal of Eating Disorders. https://pmc.ncbi.nlm.nih.gov/articles/PMC11110272/

National Center for Biotechnology Information. (2018). Treatment, outcome, and prognosis of anorexia nervosa. The Lancet Psychiatry. https://pmc.ncbi.nlm.nih.gov/articles/PMC5764193/

The Gaudiani Clinic. (202). Hypermetabolism in eating disorder recovery. https://www.gaudianiclinic.com/gaudiani-clinic-blog/2021/1/28/hypermetabolism-in-eating-disorder-recovery

The Renfrew Center. (n.d.). Hypermetabolism and eating disorders: What you need to know. https://renfrewcenter.com/hypermetabolism-and-eating-disorders-what-you-need-to-know/