Exercise, addiction, and withdrawl

New research points to the potent addictive effects of excessive exercise. When exercise-addicted rats were given naloxone, a chemical used to block the effect of opiates, they experienced withdrawl effects, such as "trembling, writhing, teeth chattering, and drooping eyelids," whereas inactive mice did not.

From a press release:

The active rats who had access to food for only one hour a day both ran the most and displayed the most severe withdrawal symptoms. Like people with anorexia athletica, they ran so much that they lost significant amounts of weight. Additionally, the more a given rat had run, the worse its withdrawal symptoms after naloxone. In contrast, regardless of how much they ate, inactive rats responded very little to the drug.

Because of the way the active rats responded to naloxone, they seemed to have undergone the same changes in the brain's reward system as rats addicted to drugs. "Exercise, like drugs of abuse, leads to the release of neurotransmitters such as endorphins and dopamine, which are involved with a sense of reward," noted [lead researcher Robin] Kanarek.

Insights into behaviors that trigger the release of the brain's "reward" chemicals may lead to addiction treatments that incorporate moderate exercise, according to the researchers. The findings also suggest that active rats given limited food may make a good experimental model for studying and developing treatments for anorexia athletica, added Kanarek.

The paper itself (free and full-text!), "Running and Addiction: Precipitated Withdrawal in a Rat Model of Activity-Based Anorexia," had some very interesting findings. There, the authors directly linked the commonalities between drug and exercise dependence. They found that "excessive running shares similarities with drug-taking behavior."

Similarities between the effects of exercise and drugs of abuse extend beyond opiate drugs. Research demonstrating that rats will perform operant responses to obtain access to either drugs of abuse or a running wheel provides evidence of the rewarding properties of both drugs of abuse and running. Moreover, under certain circumstances, such as food deprivation, both drug selfadministration and running escalate and become maladaptive behaviors. These findings suggest that running may be able to substitute for drug-taking behavior. In support of this suggestion, rats running in activity wheels self-administered smaller quantities of opiates, alcohol, and psychomotor stimulants (e.g., amphetamine and cocaine) than rats housed in standard cages.


The finding that symptoms resembling those of opioid withdrawal occur in food-restricted active rats may have correlates in clinical populations. Excessive exercise is a common symptom of eating disorders, particularly anorexia nervosa Initially, physical activity is used as a means of weight control, but with time it can become an end in itself. In the extreme, individuals with eating disorders can have difficulty refraining from exercise despite adverse physical consequences (e.g., an unhealthy decrease in body weight; decreased bone density; stress fractures). Additionally, symptoms reminiscent of drug withdrawal, including anxiety, depression, and irritability, often develop when these individuals are unable to exercise. The high comorbidity of drug abuse and eating disorders provides further evidence of a common neurobiological basis for these disorders.

The authors also found that female rats showed much higher rates of excessive running than male rats under similar conditions. Furthermore, the authors noted that they were unable to determine whether the withdrawl was specifically due to the increased exercise, or whether it was confounded by differences in food intake and body weight in the active rats.

I would also be curious to see if people with exercise addiction have higher or lower rates of opiate abuse. I could see it go both ways: higher levels of abuse because your system is "primed" for the flood of endorphins, or lower levels because you're getting those endorphins via exercise. It would be interesting to look at how other addictive behaviors overlap in EDs, and whether relatives of those with exercise addiction have higher rates of other addictive behaviors. The authors also suggested that moderate exercise might be a good prescription for those addicted to opiates as it is a non-maladaptive way to get that nice endorphin rush, though I would be hesitant given the known neurochemical overlap between these two addictions.

To me, exercise was a very safe and egosyntonic addiction. Whereas random strangers would have been alarmed if I started shooting heroin (which, given my OCD-related AIDS fears would seriously never ever happen), but they told me how "good" and "dedicated" I was when they learned about just a few of my exercise habits. If exercising X hours each day makes me "good," I figured, then the actual Y hours that I do must make me "fantastic!" I wasn't going to be arrested for having gym shoes on me, or a collection of rank sports bras in my closet. I am almost pathologically risk-averse, so exercise is probably the ultimate addiction for my personality, and I fell in to the trap head-first.

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chylo said...

There are a lot of programs that push running as a part of a recovery program from drugs/EtOH.


I think you're probably right about other personality traits deciding *which* activity we get hooked on. I too couldn't imagine doing anything illegal, but running? Hell yeah. Even through all the stress fxs and cardio problems when it was obviously destructive, it still didn't feel like something "wrong" or shameful the way I imagine I'd feel if I was doing drugs.

I wonder if, for people who aren't likely to become addicted to exercise, running programs help prevent relapse or even initial addiction by providing some other kind of reward?

Have you ever been able to exercise in moderation/non-addictively?

I'm starting to get back to serious mileage again (with full approval from the powers that be & a clean bone scan) and it's v. hard to keep myself from jumping over that edge again.

Yes, running does provide me with an outlet, a connection to my body, a way to relax. But this feeling gnaws away at me too-- I want it more & more.I have a strict plan about how much/how often I can run & that's helped so far.

I really feel like I have to carve out entirely separate patterns of exercise for a long period of time before my brain "gets" that I'm doing it differently this time.

This after a 2ish year hiatus from running, which I had hoped would be enough to give me a clean slate here.

Alexandra Rising said...

Just commenting to say I really like this post.

Carrie Arnold said...


Yes, I have been involved in activities in a non-addictive manner. That's what I'm currently working on with my therapist- fun activities that my brain doesn't latch onto as "exercise, more more MORE!" I'm thinking I'll need to stay far away from machines, but I'll probably start with some yoga or maybe karate, and I'd love to start Irish dance lessons.



Melanie S said...

Must remember that opiate addiction doesn't automatically equal heroin. Many, including myself, get addicted to perfectly legal, doctor prescribed opiates/opioids.

But, aerobic exercise is one of the most commonly suggested activities for someone trying to get of opiates. But, I myself get a little obsessive and attached to my runs. For me, they satisfy my reward system...big difference though is the effort required. When my depression gets really bad, the opiates are the way my brain goes. I can't be bothered with the effort of running for my good feeling.

Constant, repetitive exercise excites the opioid receptors in the brain in much the same way as opiate drugs. So, this study's results don't surprise all that much.

Carrie Arnold said...

You're right- opiates are far more wide-ranging than just heroin. I suppose since that has been the opiate of choice in my extended family, it kind of pops into my mind first.

A good book on prescription opiate addiction is "The Addict" by Michael Stein. Even reading that, I could understand many of the aspects of the person's addiction, but I lack the drive? energy? balls/ovaries? to buy drugs on the street. Maybe I'm supremely sheltered, but I wouldn't know where to start. I have also had a heinous reaction to Vicodin (do NOT take these on an empty stomach), so I tend towards the prescription ibuprofin and crossing my fingers that it doesn't dissolve my stomach. Even the time before that, I was so afraid of becoming hooked that I didn't get up to a high enough dose to kill the pain!

Cammy said...

Fascinating, can't wait to read the study. Exercise addiction is currently the biggest monkey on my back, and although there is no history of hard-core drug abuse in my family, alcoholism is rampant. Being the control freak/people pleaser that I am, endorphins are a much "safer" and socially acceptable substitute, exactly like you described. Peas trying to break out of the same pod. ;)

And I heart you, Carrie, for teaching me the word egosyntonic.

Anonymous said...

The problem I have is with the term "excessive". What does that mean, and who decides? When I started running, over 25 years ago, it had nothing at all to do with weight loss. It was, however, related to a need to be active, out of a sense that all I did was sit on my ass all day and night (I was a nerdy college student). I lost a little weight, very gradually, maybe about 10 lbs, but I definitely ate enough to balance the increased calorie-burning. Over a few years, I gradually got to the point where I was running 30-40 miles per week. Excessive? Yes, to many of my friends and family who were far less active, but no to some of the runners I knew who put in even more miles. Addicted? Some might say yes because if I missed more than 2 days I'd get agitated, cranky and lethargic. But I'd rather have that addiction than many other possible ones.

My point: I'm a bit skeptical of studies like this, when extrapolated to the general population. I think people have different tendencies toward addiction, and those who tend to be more addictive will exhibit that in a variety of ways, exercise, alcohol and drugs being but three examples.


RCK said...

This is a great post, Carrie. I've thought about ED in terms of addiction for a long time, and (rightly or wrongly, who knows) I've learned that my relationship to exercise is like that of a former alcoholic--can't have "just one" or I'll fall off the wagon. Which, in my case, means starting to run and restrict again in deliberately self-harming and self-denigrating ways. It's very strange to have to set limits around something that is so socially over-prescribed, particularly when a moderate amount of exercise is so helpful for anxiety and depression--but it's so necessary. I think I know as many *compulsive* exercisers as people with eating troubles.

Genetics and addiction are hand-in-glove twins, as far as I'm concerned--it's amazing to see how one person's brain will light up or go haywire with a particular substance, even in small amounts, and another person's won't. It's fascinating (not enjoyable, but definitely interesting) to notice correlations between my ED behaviours and other potential addictions--exercise, yoga, religion, alcohol, cigarettes, coffee, tea, diet coke, whatever--they all seem to trigger the same sorts of compulsions, obsessions, and cravings that anorexia and bulimia have done.

My question for myself is, how much of that reaction can be 'unlearned' or re-programmed into the brain through cognitive therapy, and how much is simply innate, always lurking inside waiting to explode? Sigh. Sometimes it would be so nice to just go for a run or have a beer disinterestedly, without wondering what kind of a mess the brain is going to kick up. If moderation were such a simple thing...

Carrie Arnold said...


There have been several studies looking at what constitutes excessive exercise, and the most useful definition came from this paper, which said that exercising to control weight/shape, and extreme guilt if you miss an episode of exercise are the two criteria that most correlate with pathology.

I do think there is a difference between excessive exercise and exercise addiction. But many people don't realize that exercise can be physically addicting, and this paper simply showed that exercise is addicting in the same way that opiates are. Not that everyone who exercises will become addicted to it, just that the dopamine system is activated during prolonged exercise and blocking the endorphins can cause withdrawl.

Carrie Arnold said...

Sorry- forgot to include the link to the study!

An update on the definition of "excessive exercise" in eating disorders research

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I'm a science writer, a jewelry design artist, a bookworm, a complete geek, and mom to a wonderful kitty. I am also recovering from a decade-plus battle with anorexia nervosa. I believe that complete recovery is possible, and that the first step along that path is full nutrition.

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