Gastrointestinal (GI) Issues During and After Eating Disorder Treatment

By Dennis Gibson, MD, FACP, CEDS

As if recovery wasn’t already difficult enough, there are often physical discomforts too.

Though reading this blog will not make your stomach feel better, it may provide you with some knowledge to help you better understand what you are experiencing.

DISCLAIMER: Every person experiences recovery differently. You may experience some or none of the things I will write about in this blog. The goal is to understand that gastrointestinal (GI) issues during treatment and recovery are very normal. Indeed, one study found that up to 97% of people experienced some sort of GI complaint before treatment even began. Let’s start by looking at some of the things that take place when we go into a state of malnutrition, as these may help you understand why coming out of a state of malnutrition is a big deal and sometimes uncomfortable.

What happens When Your Body Enters Into a Period of Prolonged Energy Defecit?

Your Metabolic Rate Decreases

As you eat less and less and your body weight begins to drop, the body reduces your metabolic rate to run more efficiently. This includes slowing of the movement of food through the stomach or delayed gastric emptying (gastroparesis). Peristalsis is the movement of food along the gastrointestinal tract, and it is performed by the muscles that surround the entire GI system. The rate of peristalsis is controlled by the pressure that is created when the stomach is stretched when food is eaten and hormonal secretions that happen in response to eating food. When you are starving, this movement slows down to preserve energy and increase nutrient absorption from the food that is consumed.

With gastroparesis, you can feel full for longer periods of time after eating. This can certainly be problematic when you are trying to eat a lot of food, but you already feel physically full. The good news is it won’t stay like that forever. During treatment and recovery, your GI system re-adapts and becomes re-trained back to normal functioning.

Endocrine responses to energy deficit can also occur (such as decreased thyroid hormones, insulin, testosterone, and leptin; and increased levels of cortisol and ghrelin) resulting in decreased thermogenesis (causing you to feel cold) and overall decreased metabolic rate. Low energy intake and minimal body fat are perceived as indicators of energy unavailability — your body assumes that there is no food in the environment — resulting in these hormonal changes aimed at conserving energy and promoting energy intake. This, as you can imagine, has several implications for the optimum functioning of the body.

Your Energy Reallocates

The body starts to reallocate energy only to organs that are vital for survival rather than for optimal functioning. Another way to think about this is like a wage cut--you are going to stop spending as much money on luxury items and allocate everything that you have to necessities. If the decrease in wages continues to be less than you need to spend each month, you will gradually cut back more and more. Your body will get desperate.

Mental energy gets allocated away from more interesting things such as work, people, hobbies etc. and is instead put towards thinking about food, as your brain assumes that your decrease in intake is due to you forgetting to feed yourself well enough, or not enough food so you need to look for more. You will notice that you are thinking of food all the time and unable to hold much interest in other things. This is your body trying to motivate you to search for and consume food — this makes not being able to eat even more painful.

Also, for some of us, when we go into an energy deficit, we feel like we have more disposable energy—we don’t. Similar to what we learned in elementary school about animal migration when environmental resources become scarce, some humans may also experience a proclivity to movement created by the energy deficit. It is not that you really have more energy, it’s that your brain is signaling you to move and find more food.

That said, even if you feel like you have energy, expending it comes at a cost. Just because you feel like you want to move doesn’t mean you have excess energy at all. Spending that energy in the gym or out running means that you are effectively wasting it, and that energy is taken from your organs that so desperately need it.

What Happens When You Start Eating More?

One thing to look out for if you are very malnourished is refeeding syndrome — shifts in fluid and electrolytes due to moving from a state of tissue breakdown (catabolism) to a state of building up of tissue (anabolism) when you start to eat more food. If the body immediately starts to make more energy as you eat more food and doesn’t have the nutrients and building blocks required to meet the demand of processing more energy, this can cause problems. If you are eating a very low amount of food, or at a very low weight, you should be monitored by professionals to make sure you are safe.

Water Weight/Bloating

In the early stages of refeeding, you may feel that you are gaining weight rapidly. Rest assured—you are not. Any rapid weight gains early in refeeding are due to fluid shifts and water retention. This can happen for various reasons, including your body trying to achieve rehydration, as your body can hold on to water in a way that it cannot hold on to food. Of course, your eating disorder thoughts will tell you that you are broken and that you have suddenly overnight gained a large amount of weight. Again, you haven’t. It would be impossible for you to gain several pounds of bodyweight in a day.

Stomach Problems in Anorexia Nervosa

Why does your stomach hurt? Lots of reasons why and it has every reason to feel that way!

  • Common physical effects include gas, bloating, diarrhea, nausea, constipation, acid reflux, frequent bowl movements, indigestion. None of these things are particularly fun but they are all also very normal, and to be expected in recovery. Your stomach and intestines have not been given any maintenance or repair work due to lack of food. Before this system is going to work well again, repairs will have to be undertaken. Delayed gastric emptying means that food empties very slowly from your stomach, and this food retention long after eating can make you feel overly full, bloated, nauseous, and just overall uncomfortable. Constipation due to slowed peristalsis can also contribute to your GI symptoms.
  • Low volumes of food over time leads to shrinking of the stomach. When you start to eat again, you will be uncomfortably full until this rights itself and your stomach expands. Again, we need to train the system back up.
  • Restriction leads to several changes, including a reduction in the amount of “good bacteria” in your gut. So, when you start eating again, the lack of diversity in your gut may be responsible for the bloating, gas, etc. The important thing to note is that you must keep eating for the bacterial diversity in your gut to re-establish.
  • When you have been eating limited types and overall quantity of food, your GI tract will be out of practice for processing food. This can also contribute to loose stools and some of those annoying GI symptoms discussed above. Practice makes perfect — keep eating.
  • With eating disorders comes anxiety with food completion. The sympathetic nervous system--that system responsible for “fight or flight”, increases activity with anxiety. Unfortunately, we were not designed to digest food well while anxious. However, as this anxiety improves and you feel less anxiety about eating, your digestion can improve.

Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome, a type of functional GI disorder (FGID), is common in eating disorders and malnutrition. We are still in the early stages of understanding FGIDs but they are characterized by GI symptoms resulting from abnormal functioning within the GI tract and/or altered pain perception from signals sent from the GI tract to the brain. Therefore, not only does weight loss lead to those GI changes discussed above but those changes may be even more intolerable due to changes in pain perception. Fortunately, nutrition also changes the interpretation of these signals from the GI tract to the brain (and vice versa, from the brain to the GI tract; this is known as the gut-brain axis), and these FGIDs improve with treatment.

Temporary Food Intolerances

In my career, I have seen hundreds of patients who have become concerned that their GI symptoms are food allergies. This leads to testing that then becomes interpreted as a food allergy. Fortunately, 99% of the time these are not allergies but instead food intolerances that have developed due to the malnutrition/eating disorder and the associated difficulties with digestion due to the unhealthy state of your gut. Patience is key—these intolerances usually disappear with treatment.


The sensation of hunger is a complex neurobiological mechanism that is at least partially regulated by various hormones, brain circuits, and signals sent to the brain from the GI tract, all of which become dysregulated with malnutrition. The lack of hunger experienced by many individuals with eating disorders can make eating that much more difficult, as well as the further dulling in hunger cues due to the gastroparesis described above, but treatment with weight restoration is ultimately necessary to turn those hunger cues back on. And please don’t start to believe that further treatment is not needed if hunger cues are already present.

Weight Gain

Weight gain will complicate your mental processes and cause you to want to go back to restriction — fear of weight gain is a common response that is generated by eating disorders. Be ready for it and commit to eating regardless of how you feel about it. Weight initially gathers around the vital organs so try to understand that the weight gain is truly saving your life. Over time, this weight distribution will normalize.

What Do You Do?

  1. Continue to eat at regular intervals regardless of how uncomfortable it feels.
  2. Drink adequate amounts of water and fluids without water-loading.
  3. Rest. You have a lot going on. Take recovery patiently and seriously.
  4. Work with a professional to help choose appropriate foods for treatment that could also lessen the GI symptoms you experience.
  5. Work with a professional to monitor for any refeeding syndrome or other medical concerns.
  6. Did I mention that you must continue to eat?


The Endocrinopathies of Anorexia Nervosa

Zipfel S, Sammet I, Rapps N, Herzog W, Herpertz S, Martens U. Gastrointestinal disturbances in eating disorders: clinical and neurobiological aspects. Auton Neurosci 2006; 129:99–106.

Avoiding medical complications in refeeding from Anorexia Sachs K, Andersen D, Sommer J, Winkelman A, Mehler PS. Eat Disord. 2015; 23(5):411-21. Epub 2015 Mar 9.

Benini L, Todesco T, Dalle Grave R, Deiorio F, Salandini L, Vantini I. Gastric emptying in patients with restricting and binge/purging subtypes of anorexia nervosa. Am J Gastroenterol 2004; 99:1448–1454.

Soul S, Dekker A, Watson C. Acute gastric dilatation with infarction and perforation. Report of fatal outcome in patient with anorexia nervosa. Gut 1981; 22:978–983.

Written by

Dennis Gibson, MD, FACP, CEDS

Dennis Gibson, MD, FACP, CEDS serves as the Clinical Operations Director at ACUTE. Dr. Gibson joined ACUTE in 2017 and has since dedicated his clinical efforts to the life-saving medical care of…

ACUTE Earns Prestigious Center of Excellence Designation from Anthem
In 2018, the ACUTE Center for Eating Disorders & Severe Malnutrition at Denver Health was honored by Anthem Health as a Center of Excellence for Medical Treatment of Severe and Extreme Eating Disorders. ACUTE is the first medical unit ever to achieve this designation in the field of eating disorders. It comes after a rigorous review process.

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