THE METABOLISM, HYPERMETABLOLISM AND IMPLICATIONS FOR RECOVERY FROM A RESTRICTIVE EATING DISORDER
October 2022 – UPDATED AND REPOSTED DUE TO THE POPULARITY OF THE POST
A question that arises regularly from people in recovery from an eating disorder (ED) is in respect to issues around body metabolism, in terms of what it is; what hypermetabolism is; whether they have ‘broken’ their metabolism and what it means for their recovery.
I hope to address a lot of the common concerns people experience around this topic in this post.
If you have had or have disordered eating then it is likely that your body metabolism has been affected at various points, impacting on your body’s ability at those times to lose or gain weight and to function at an optimal level.
What Is The Body Metabolism?
The metabolism describes all the chemical processes that go on continuously inside your body to keep you alive and well; your organs functioning so that your heart beats and lungs work to breathe, cells repair, your gut digests food and your brain can think.
In every moment, your body is undertaking thousands of chemical reactions to keep your cells functioning and to ensure that you stay alive!
To stay alive, the body needs essential energy and nutrients which come from the food you eat and the fluids you drink. The body then breaks these foods and drinks down (which in itself takes energy) to release the energy from them and this energy is then used for all those bodily functions that you need to have working well in order to be as optimally healthy as possible.
Basal Metabolic Rate
Even when completely resting, your body is using up calories to just maintain its basic function (as described above).
The minimum amount of energy required to carry out these resting chemical processes is called the basal metabolic rate (BMR) which accounts for anything between 60% and 75% of the body’s daily energy requirements (in a sedentary person) depending on other factors such as age, lifestyle, the body make up and your environment.
What Happens When The Body Has Insufficient Energy
When the body is starved (i.e. the energy consumed is lower than the energy required), its tissue, including muscle and fat, is lost and this triggers a reduction in the metabolic rate.
If the body does not have sufficient energy intake, it will try to preserve every bit of energy it does get in any way it can. This is commonly referred to when speaking about eating disorders and malnutrition as the body going into ‘starvation mode’.
The mechanisms the body uses when in starvation mode in order to stretch out the little energy it has been given include providing less nutrients to hair, skin and nails (so they become dry and brittle); slowing the heart rate down, slowing down the gut motility (leading to digestive problems, feeling overly full on little intake and potential constipation) and reducing the body temperature (often leaving the person feeling cold most of the time).
This ultimate drop in the BMR means that the body needs less calories to function but is functioning at a very basic level, ultimately just doing all it can to stay alive.
A drop in BMR will happen in the body when the energy intake is dropped for any reason. Therefore, in eating disorders, it will occur when the person is not eating sufficiently (restricting) or when a person is compensating for what they are eating (e.g. via exercise, purging etc).
However, the same response occurs when people drop their intake for other reasons, including people who diet and this explains why those who diet may initially lose weight rapidly but after a couple of weeks of dieting will find it much harder to sustain weight loss as their BMR has fallen and they are using less baseline energy.
Once a person who has had a low BMR starts to eat more again and provide their body with the energy it requires, the metabolism will start to rise again and as the body’s systems return to working at their optimal and healthiest levels, the body will require more energy (food) just to keep maintaining these basic functions.
The Metabolism In Eating Disorder Recovery
In eating disorder recovery weight restoration and nutrition are key components to treatment, in order to restore the person’s body to its natural set point weight.
This very necessary weight gain in recovery results in ultimate improvements in the physiological and psychological complications of semi starvation.
In order to achieve weight gain, people with an eating disorder ultimately need to increase their dietary intake to a level that is above that required for their BMR AND daily activities AND then enough to restore weight in terms of tissue re-development and internal repairs.
To achieve regular weight gain and find their own unique set point weight (for ultimate long lasting health), people recovering from eating disorders generally need an escalating calorie intake.
Hypermetabolism in Eating Disorder Recovery
Research has found that women with eating disorders tend not to gain weight if fed the energy requirements of healthy adult women who have never had an eating disorder. Instead people in recovery from eating disorders tend to have much larger energy requirements and need to increase their intake more and more for sustained weight gain.
The reason for this can be explained since people with eating disorders are often found to become hypermetabolic once they increase their dietary intake sufficiently. This is where their metabolic rate becomes much higher than the average rate expected in a healthy adult woman.
Hypermetabolism in people recovering from an eating disorder results in them potentially losing weight more easily (if not careful) and their energy (food) requirements to gain weight is much more than most ‘normal’ people would need.
People with eating disorders have also been found to commonly become hyperthermic during their recovery. This is where they convert more of their energy intake to heat than healthy people, rather than use the excess intake to build tissues. As a result, during nutritional rehabilitation, people with an eating disorder often become hot and sweaty. This is commonly worse at night and it is not unusual for people in eating disorder recovery to wake in the night sweating and with soaking sheets.
Conversely, healthy individuals who have never had an eating disorder will generally drop their body temperature at night and so preserve energy at this time.
It is thought that the hyperthermic effect during nutritional rehabilitation results in up to 30% of energy input being lost (in healthy people the rate is generally around 14%).
Weight Gain in Terms of Fat vs Other Tissues In Recovery
In order to fully weight restore and achieve a lasting recovery, the body needs to restore fat mass AND fat free mass.
To gain fat free mass the energy requirement is several times greater than that needed to gain fat mass but in order to achieve a full and lasting eating disorder recovery (reaching your body’s genetic set point weight), it is essential to go through the nutritional rehabilitation process and fully restore both body mass types. As the body gains weight and restores in recovery, it will gain a greater proportion of fat mass first and the final (crucial) stages of weight restoration will then include building more essential muscles and tissues, which as stated above, takes even more energy. Therefore, this vital latter stage of weight restoration and physical healing can be even harder to achieve as it needs more food (energy) to achieve the same rates of gain that were made earlier in the process.
What Happens To The Metabolism After Weight Restoration?
After the nutritional rehabilitation phase of eating disorder recovery and once the person is fully weight restored, it has frequently been reported that their energy requirements remain high. Those with an eating disorder and in recovery are frequently found to still be very energy inefficient and need greater calorie intakes than healthy controls just to maintain their restored weight.
It is not uncommon that nutritionally rehabilitated people need up to twice the daily calorie intake to healthy adults just to maintain weight due to ongoing hypermetabolism.
This hypermetabolism can settle down in 6 months of nutritional rehabilitation but it is widely recommended that the best chance of long term weight maintenance in recovery (reducing the risk of any relapse) is to persist with high calorie intake long term.
What Does All This Mean If You Are In Recovery From An Eating Disorder?
For anyone in recovery from an eating disorder it is likely that once you are providing your body with sufficient energy on a daily basis (i.e. high calorie intakes) your body metabolism will speed up to a greater rate than in healthy individuals.
Therefore, you will likely find that your energy requirements to keep gaining weight will keep rising and as you start to fully restore both fat and fat free mass towards the the end of weight restoration, your energy needs are likely to be extremely high.
During nutritional rehabilitation you might find that you are warm or hot a lot of the time and experience night sweats or clamminess.
You will possibly notice a rise in your heart rate.
You should also start to notice better nails, hair and skin.
Once you have fully weight restored, the level of intake (food) you need every day to maintain this healthy weight is likely to be significantly higher than healthy adults of your age and build and this higher energy need could continue for a significant amount of time.
In conclusion, the amount of food needed now to restore weight and once weight restored is likely to be much more than you think and your body will respond to the energy levels it is given.
Therefore, eat large amounts to nutritionally rehabilitate and keep eating large amounts well into recovery!
And Finally, But.. Is My Metabolism Broken??
One question that is often posed from people in recovery from restrictive eating disorders who have been weight restoring while still actively restricting or actively exercising is –
…‘but what will happen now if I do stop restricting or stop exercising?’
‘I am already back at a ‘healthy weight’ – won’t I just then become massively overweight? Have I broken my metabolism forever??’
If this describes your situation or your fears then please don’t despair – you are not broken!
It is very likely that as you have still been restricting your intake and exercising then your body metabolism has remained in ‘starvation mode’ (very low) to preserve what it is being given. Your body used the small amount of surplus energy you did provide it with to restore your weight and try to repair tissues causing some weight gain but your body recognised that there was still insufficient energy supply to allow it to speed up the base metabolism and function at its optimum.
This can still be changed.
If you start to eat more now – stop restricting your dietary intake and give your body the amount of fuel it desperately still needs and if you stop compensating for what you are eating (if you are still exercising) then your body will respond.
Your body will learn to trust that fuel is in sufficient supply so it can ‘afford’ to work at a more optimal level and your metabolism will, as discussed earlier in this article, respond and speed up. It is never too late for this to occur!
Consistently eat unrestrictedly, without compensating and your metabolism and body weight will naturally settle back at your genetic set point which your body will then fight to maintain.
Marzola et al. Nutritional Rehabilitation in Anorexia Nervosa: review of the literature and implications for treatment. BMC Psychiatry (2013) 13:290