More on hypermetabolism
I had mentioned about a week or two ago that I was going to begin a blog series on the biology of eating disorders. I wanted to start with something about the causes of EDs or something like that, but I think this topic is extremely relevant and so we can just call this the first post in the series.
I did some more research tonight into the biology and etiology of hypermetabolism. So let's start with a basic definition from Wikipedia:
Hypermetabolism is the physiological state of increased rate of metabolic activity. The impact of the hypermetabolic state on patient nutritional requirements is often understated or overlooked. Hypermetabolism typically occurs after significant insult to the body. In hospitals and institutions, the most common causes are infections, sepsis, burns, multiple trauma, fever, long-bone fractures, hyperthyroidism, prolonged steroid therapy, surgery and bone marrow transplants.
And, yes, eating disorders. Specifically anorexia. As someone falls deeper and deeper into anorexia, their metabolic rate slows dramatically. During the Minnesota Starvation Study, resting energy expenditure (also known as basal metabolic rate- the amount of calories needed just to keep your body functioning and doesn't include ANY physical activity) fell by about one-third. The book "Introduction to Clinical Nutrition" says that
Starvation involves metabolic alterations that enhance the chance of survival by increasing the use of body fat stores, by sparing the use of glucose, by minimizing nitrogen loss, and by decreasing energy expenditure.
But when the ill person begins eating again, their metabolism kicks into high gear. Body temperature rises. A person can experience night sweats, which may also be related to hormone function returning to normal.
Why? It seems a remarkably inefficient use of resources. And indeed, hypermetabolism may not be entirely adaptive from an evolutionary standpoint as the body's use of food becomes remarkably inefficient. Even so, the body needs tremendous amounts of energy to replace lost fat and muscles stores, depleted organs, bone mass, hair, nails, you name it. No organ system is spared during an eating disorder.
The amount of calories needed for people with anorexia to return to a healthy weight can vary by illness severity (a lower BMI means more calories, as well as duration of illness), and by illness subtype. One study found that those with the binge-purge subtype of anorexia needed significantly fewer calories than those with the restricting subtype; another study found that calories were about the same. Other variants include your metabolic rate before illness onset. I've known several good friends curse their fast metabolisms quire vociferously during refeeing.
When looking at the phase after weight restoration, caloric needs between people with anorexia nervosa and those with bulimia nervosa turn out to be quite different. One study found that people with AN needed more calories per kilogram of body weight than normal controls, while those with BN needed fewer. It appears that people with a current diagnoses of BN but a history of AN require more calories than those with BN alone. Further, people with the restricting type of AN needed more calories than those with the binge-purge type, both of which were greater than patients with BN (some of the studies cited above show that, for weight maintenance, caloric needs are basically the same for any patient with a current diagnosis of AN).
Some of these differences may rest in premorbid differences in metabolic rate. It makes intuitive sense that a person who finds it easy to lose weight would have a faster innate metabolism. Other reasons calorie needs may remain unusually high for a person even after weight restoration is the sheer amount of rebuilding the body needs to perform. Bulimia is violently destructive to the body, and I would never say differently. However, some of the damage done by anorexia is slightly different, and the body must rebuild and repair essentially every organ in the body. My psychiatrist told me that the nerves continue to repair themselves for up to two years after weight restoration. This can hardly be the only organ system taking a long time to recover.
How long hypermetabolism lasts will probably vary from person to person, and depends on how long you were sick, how your body responded to the damage from your eating disorder, your activity levels, among others. There's no real way to be sure. If your caloric needs are unusually high--even for hypermetabolism--you can have body composition analysis and resting energy expenditure testing done. Personally, I think this is best left to extreme cases since so many of us have a tendency to fixate on numbers.
I hope this helps explain hypermetabolism just a little bit. I can't answer every question, as it's been a long time since my college biochemistry days, but I can always look things up.
26 comments:
I've always found hyper-metabolism fascinating. I have a question though, which you may not have the answer to....
I've done the refeeding thing several times and been hyper-metabolic when in intense treatment. However, there have been times when I was outpatient and would eat MORE... but not technically ENOUGH... and I would gain weight much faster than the inpatient times. Why is that? I guess I just don't understand why sometimes you are hypermetabolic and other times you are not? It's something I've always been curious about.
Great post -- I love this stuff.
Regarding "Why?" here's an uninformed guess.
Nutrition is not just about calories. Calorie intake and use is a rapid cycle, but other nutrients like minerals and some vitamins have a much longer cycle. Even protein, in a hunter-gatherer diet, was a long-term asset.
You see this in modern times in places where food is plentiful, but it's only low-protein food like grain. People have to eat far more calories than they really need to survive, just to get enough protein.
So, to restore other nutrient levels quickly when food is plentiful after a period of starvation, it may be efficient for the body to waste calories.
GT,
Part of the reason may be that you weren't stoking the metabolic fire as much as an outpatient, and it slowed down a little. Because if you're not eating enough, your metabolism won't be able to really ramp up.
cbtish,
Very good point about the protein. An unavailability of nitrogen is one of the things that can stimulate hypermetabolism, as protein has nitrogen while carbs and fats do not.
What kind of damage is caused to the nerves from anorexia?
What kind of damage is caused to the nerves from anorexia?
Anon,
I don't know about every different type of damage, but the most common comes from a lack of fat in the diet. Nerve cells (like ALL cells) have a coating of lipids; without that membrane, it can't conduct the electrical impulses properly. Some common problems include numbness and tingling in the extremities. Occasionally, the damage can be permanent, but it usually goes away not just with weight restoration, but also with making sure you eat enough fats.
Starvation also slows down the electrical impulses in the nerves, which leads to a lack of coordination. This is amplified by the electrolyte imbalances common to both anorexia and bulimia.
Hey Carrie,
I was wondering if with all your wisdom you could answer a question for me. . .
The last two times refeeding I have been hypermetabolic -- this time, as an outpatient, I am gaining on much fewer calories (though my weight is lower). My dietican assures me that my BMR may not have caught up yet with my weight/refeeding. Have you ever heard this happening to anyone?
A
just, in agreement/commiseration with others, my body's reaction was different every time I went into treatment! I'm BN and yet 2 times I went hypermetabolic and others my metabolism was painfully slow. who knows! different time, different age, different severity of symptoms.... I dunno!
Recovery requires so much patience!
A,
Yes I've heard of it, but no, I don't know why. I think to some extent, you need to be eating enough for your body to launch into hypermetabolism (though not always).
Laur,
You're right- it does vary. Greatly!
Does hyper-metabolism happen to all anorexics, I mean, is it a qualification of an anorexia diagnosis?
I am thirty and was first diagnosed an at 14. i relapsed at 17 and at 27. I do not have to eat a lot to maintain my weight, i have always regained rather quickly. Also, I was an early bloomer, a normal/large kid who did not need to eat a lot to have a healthy weight. I think that is why my e.d. started, i just felt so huge for no reason. Could I just have a naturally slow metabolism? I met standards for a diagnosis but I was never severe - no tube or anything. Losing weight has always been a slow process, even at my sickest when i was barely eating and over exercising. I don't really understand what is going on with my metabolism and have never felt comfortable discussing with medical professionals.
Anon,
I'm not sure whether hypermetabolism happens to everyone. I don't think it does, especially if you've had an ED for a long time. Also, the fact that you mentioned you had a slower metabolism to begin with might have made a difference.
But no, it is *definitely* not the criteria for diagnosing AN.
Thanks for writing!
Laur! I'm sorry- I just checked your profile and realized how I knew you! Hope things are going well.
sunkeThis is Laur, posting from work.
Hey, yeah, I should have introduced myself.
It's been a long time!
but yeah, I think we were both on SF, you sent me mail when I was in Philly (on Hogwarts stationary, I believe!) and I gave your first book a stellar review on amazon!
:-)
Hi Carrie,
I am someone who is recovering from an eating disorder and recently relapsed. However, my relapse was not to a point where I was eating a starvation level of calories, but closer to about 1300-1600 most days with some variation. However my BMI is now very low again and I've recently been eating back around 2500 calories with some days over that. Before, I was eating 3000+ and yet this time around I've already "put on" about four and a half pounds in six days. That's not humanly possible, is it? I don't know. I know I should not be weighing more than once a week and probably not at all for a couple of weeks while adjusting to my high intake again due to water retention and such, but I'm worried I have screwed up my metabolism because I did not technically "starve" to lose weight this time even though my weight is low again. Will my body still have damage to repair, to expend those extra calories on? Organs, and so on? Does this rapid gain stop?
What is your view on this? If it makes any sense at all. I know I am rambling somewhat.
Anon
this article explained a lot! I have a question though, when I was inpatient, I had really bad night sweats...how'ever they went away but now they keep coming back on and off...its been 6 months and it still kicks in and out...I dont really understand what is happening
Thanks!
D
Hi Carrie,
Really enjoyed your books and blog. We've been refeeding my 15 year old with RAN sor almost 11 weeks (she's gained about 13 pounds) and is quite warm usually. Her feet and hands swell and get red/hot usually in the morning and at night. Not sure if it's also related to stress. Her doctor did a thyroid check; it's fine. Have you ever heard of this? THANKS!!!
Yes, I've heard of this. I believe it's called Raynaud's Phenomenon.
You can find a link here:
http://www.medicinenet.com/raynauds_phenomenon/article.htm
Carrie,
Wow - you are good! I think that's exactly what my daughter is experiencing. Her doctor and therapists didn't know, so thanks for solving the mystery and giving me some piece of mind. Wish you could know how very, very much I appreciate it! Thanks, too, for this blog and all you are doing to help others. You are one amazing person, Carrie; don't forget that!!!
Warmly,
Laura
Is this condition only brought on by poor nutrition and eating habits or can it be a symptom to a more serious problem such as cancer? I have researched this term and not found much information about it... The condition is concerning my brother and his health. He does not have an eating disorder..but discovered a spot on his lung and an enlarged arota. Thanks
Anon,
Hypermetabolism can happen for any number of reasons, only one of which is recovering from starvation/malnutrition. Wikipedia has a decent summary if you want more information.
Hope your brother is on the mend soon.
interesting to read that most with AN b/p don't require as many calories as those with AN-r during refeeding.. i myself was AN-b/p and was hypermetabolic, requiring the highest meal plan possible (won't say numbers but was A LOT of calories)..
and at the time i was surprised, didn't think i'd need that much to gain, and i don't think my pre-ED metabolism was anything remarkable, though it was certainly at least average if not above-average. now, a diff. story :/
me again. what CBTISH said makes sense, but on an inpatient unit, the diet is balanced and not low-protein.. yet patients there experience hypermetab. i guess because with a loss of weight (ie, muscle) PRE hospitalization, there's a loss of Nitrogen?
Will everyone who has had an eating disorder (I have AN) have a hyper metabolism?
...so if someone regains weight rapidly on a low calorie level, meaning that during their "recovery" their body never got out of the adaptive thermogenesis of starvation, is it possible that a drastic increase in calories AFTER weight restoration could induce a hypermetabolic state?
...so if someone regains weight rapidly on a low calorie level, meaning that during their "recovery" their body never got out of the adaptive thermogenesis of starvation, is it possible that a drastic increase in calories AFTER weight restoration could induce a hypermetabolic state?
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