My destructive habit was nothing more than my body and brain becoming conditioned to expect and demand binges. I have identified three possible habit types to describe my binge eating—termed the "habit of excess," the "habit of pleasure," and the "habit of impulsivity"—all of which have a physical basis in the brain. I believe my binge eating was at least one (and most likely a combination) of those three habits, discussed in detail below. But first, a fuller discussion of the concept of habits is necessary so that I can explain how my binge eating became a destructive habit.
THE NEUROSCIENCE OF HABITS SIMPLIFIED
Habit formation is a simple, yet remarkable, process in the brain. A habit works like this: When we repeat a behavior many times, it causes physical changes in the brain—changes that make that behavior easier to repeat. Soon, we become so adept at performing the behavior that we can do it without much conscious thought. This is when the behavior becomes habit. Habits are unthinking and automatic, but most habits are adaptive, healthy, and necessary for our existence. To explain habits properly in terms of the brain, I'll delve here into a bit of simple neuroscience.
Our brains have billions of cells called neurons. All of our physical functions, thoughts, feelings, sensations, perceptions, moods, memories, and actions are the results of signals passing through the neurons. Neurons form connections with one another known as synapses. When a neuron fires, it transmits its electrical signal across a synapse to the next neuron, which must fire to continue transmitting the signal.
No single neuron works alone, but with the coordinated activity of many others. In order to perform any physical or mental task—from the simple act of taking a step to the more complex one of throwing a curve-ball; from saying hello to a friend to solving a complex math equation; from recalling an elaborate memory to simply feeling sad or glad—neurons have to fire in a coordinated way. "Each experience and each memory are composed of a multitude of neurons firing together at different levels of the brain and in diverse areas."91
When patterns of neurons fire simultaneously many times, the synapses become stronger and better able to transmit signals. As one neuroscience maxim has it: "Cells that fire together, wire together,"92 meaning that patterns of neurons that are used repeatedly to perform any function become connected in such a way that makes that function easier to repeat. This is a testament to the amazing efficiency of our brains.
Patterns of neurons that are strongly connected form neural pathways. We have virtually unlimited numbers of neural pathways in our brains that are responsible for our behaviors, thoughts, memories, perceptions, and, most importantly for the purposes of this book, our habits. Habits are nothing more than efficient neural pathways, created when patterns of neurons fire together repeatedly, forming powerful bonds. The habit, whether productive or unproductive, becomes easier and easier to repeat as connections between the neurons in the pathway become stronger and stronger.
The formation of habits in the brain is "analogous to the way that traveling the same dirt road over and over leaves ruts that make it easier to stay in the track on subsequent trips."93 Neurons become so well connected that the habit becomes automatic, which is advantageous when the habit is a good one, but harmful when the habit is a destructive one, like my binge eating. Once the pattern of bingeing became established, the neurons involved in it became coordinated, organized, and strong, so that I felt compelled to continue the behavior. In a real physical way, my brain became hooked on binge eating.
My habit didn't begin as a conscious choice, like many productive habits do. In stark contrast to someone who consciously practices a skill—such as playing a musical instrument, solving algebra problems, or learning to type—I felt propelled into my habit by some force beyond my control. That force was my survival instincts. What began as a survival reaction to food deprivation turned into a terrible habit because, by binge eating many times, I programmed my brain to become dependent on binge eating.
The neurons that "fired together," driving me to binge eat those first few times, eventually became "wired together," ensuring the persistence of my urges to binge. What began as a way of dealing with the threat of starvation became physically stamped into my brain, so my brain kept urging me to binge even after the threat of starvation was long gone and even after all of my weight gain. I continued to binge because I was caught up in a destructive habit—the expression of something physical going on in my brain. I didn't know that each time I followed my urges and binged, I only strengthened the neural pathways involved, making the habit stronger and making it more and more difficult to quit.
This brings me to a very important concept for understanding my eating disorder, the concept of neuroplasticity.
NEUROPLASTICITY AND MY BINGE-CREATED BRAIN-WIRING PROBLEM
In simple terms, neuroplasticity refers to the brain's ability to rewire itself.94 Neurons are not fixed, but instead have the ability to "forge new connections, to blaze new paths through the cortex, even to assume new roles."95 Only a little more than twenty years ago, neuroscientists thought that only brains of infants and young children were plastic and that the adult brain could not change. However, we now know that the adult brain can be altered too; it retains some of its plasticity throughout life.96
It is said that the brain "learns as it plays,"97 physically changing based on one's experience. The following passage from Sharon Begley's Train the Mind, Change the Brain gives a telling explanation of neuroplasticity:
The actions we take can literally expand or contract different regions of the brain, pour more juice into quiet circuits and damp down activity in buzzing ones. The brain devotes more cortical real estate to functions that its owner uses more frequently and shrinks the space devoted to activities rarely performed. That's why the brains of violinists devote more space to the region that controls the digits of the fingering hand. In response to the actions and experiences of its owner, a brain forges stronger connections in circuits that underlie one behavior or thought and weakens the connections in others. Most of this happens because of what we do and what we experience of the outside world. In this sense, the very structure of our brain—the relative size of different regions, the strength of connections between one area and another—reflects the lives we have led. Like sand on a beach, the brain bears the footprints of the decisions we have made, the skills we have learned, the actions we have taken.98
The importance of this concept in understanding my eating disorder and recovery cannot be underestimated, so I will include another explanation here—this from neuropsychiatrist Jeffrey Schwartz in The Mind and the Brain:
[T]he brain's ensembles of neurons change over time, forming new connections that become stronger with use, and letting unused synapses weaken until they are able to carry signals no better than a frayed string between two tin cans in the old game of telephone. The neurons that pack our brain at the moment of birth continue to weave themselves into circuits throughout our lives. The real estate that the brain devotes to this activity rather than that one, to this part of the body rather than that one, even to this mental habit rather than that one, is as mutable as a map of congressional districts in the hands of gerrymanderers. The life we lead, in other words, leaves its mark in the form of enduring changes in the complex circuitry of the brain—footprints of the experiences we have had, the actions we have taken. This is neuroplasticity.99
So, where we focus our attention and the actions we take physically change our brains. For example, if I concentrated on learning a musical instrument, and practiced consistently, more neurons in my brain would be allocated to that task. Neurons would form new connections as I—the musician—became more proficient, and the connections would grow stronger and more efficient with practice. It was the same with my bulimia. The more I binged due to survival instincts, the more my brain changed to accommodate the behavior. As I focused attention on food and followed my urges to binge, my brain devoted more and more neurons to my habit and strengthened the connectio
ns between those neurons. Indeed, "habits are behavioral expressions of plastic changes in the physical substrate of our minds."100
Sports coaches often say that "practice makes permanent." They use this saying in contrast to the cliché "practice makes perfect" to illustrate that practice doesn't make perfect if you are practicing incorrectly. If, for instance, a tennis player practices serving with incorrect form over and over again, the incorrect form becomes permanent. "Practice makes permanent" has a real biological basis in the brain. By practicing incorrectly, the tennis player trains groups of neurons in his brain to send incorrect signals to his muscles. The incorrect serve becomes wired into his brain as a habit.
Although it may seem difficult to think of the similarities between bulimia and an incorrect tennis serve, the two habits form in much the same way. Each time I binged and purged, I made the neural connections driving my behavior stronger and more efficient. Each binge-purge cycle was like practice that eventually made my problem permanent. During every binge, and during every purge, the behaviors and all the thoughts and feelings that went along with those behaviors got programmed into the very structure of my brain; and once that happened, my habit took over. It automatically produced urges to binge no matter how much I wanted to change.
My habit-driven bulimia was what I'll call a "binge-created brain-wiring problem." I'll use the term frequently through the remainder of the book, so I will define it here for reference:
A binge-created brain-wiring problem is a harmful brain condition that develops due to the repeated destructive action of binge eating. It is the physical expression of the bulimic habit in the brain.
By binge eating enough times due to my survival instincts, my bulimia became part of the very physical structure of my brain, which ensured that my body and brain continued to expect and demand the binges. I had wired neurons together in a way that was harmful to me. My brain was never faulty or diseased, but I had created unwanted, but fine-tuned and strong neural connections that produced destructive urges and compelled me to perform unwanted behaviors for many years.
The development of my habit of bulimia looked something like this:
Dieting —> Survival Instincts —> Urges to Binge —> Binge —> Purge —> More Urges to Binge —> Repeated Survival-Instinct-Driven Bingeing (and Purging to Compensate) —> Habit Formation in the Brain —> Brain Automatically Produces Urges to Maintain the Binge Eating Habit
I cannot pinpoint exactly when survival instincts stopped driving my behavior and habit started driving it, but I'm sure it was a gradual process. By the time my survival instincts died down, the habit of bingeing was already firmly established, which made the gradual change mostly imperceptible to me. However, looking back, I can identify one difference in survival-instinct-driven binges and habit-driven binges. In habit-driven binges, I seemed to eat a little less frantically than I did during those first several months of binge eating when I was underweight. It seems my body knew—at some level—that I didn't truly need so much food anymore, but I still felt driven toward it. Despite this minor difference, habit-driven binges still made me feel out of control and the urges still felt like a terrible intrusion in my life.
WHERE AND HOW DID THE HABIT FUNCTION IN MY BRAIN?
If I had access to neuroimaging devices, I may be able to give a firm answer to this question. But no one scanned my brain at the time, so I can't be sure where and how my habit functioned. In other words, I can't pinpoint exactly where my binge-created brain-wiring problem took hold, just as I cannot pinpoint exactly when it took hold. The specific neural pathways that drive eating disorders haven't been identified, but more researchers are studying the neuroscience of eating disorders in order to better understand them in terms of the brain.101
It's likely that an eating disorder "involves abnormal activity distributed across brain systems,"102 but currently, little is known about these brain abnormalities.103 Although we can't precisely locate where the habit of bulimia takes hold in the brain, there are still a few possibilities to present, based on what is currently known in neuroscience.
I received clues to where my habit existed during my experience on Topamax (topiramate), which provided a temporary reprieve from my urges to binge. As I talked about in Chapter 7, Topamax is an anti-epileptic drug that is sometimes used to treat bulimia and binge eating. Topamax has effects on weight and appetite and "on neural systems important in regulating eating and weight control."104 The drug is associated with decreased appetite and weight loss, at least in the short term.105
Topamax seemed to nearly shut down my binge-created brain-wiring problem for a short time; so knowing how Topamax works gives me an idea of the nature of my habit. The exact brain mechanism through which Topamax exerts its effects in bulimics isn't known at present,106 but there are three possible mechanisms that apply to my experience, all of which result from neuroplastic changes in the brain.
A Habit of Excess
Some researchers hypothesize that Topamax reduces binge eating by simply decreasing appetite and enhancing fullness107 through several possible neural pathways. One possibility is that Topamax reduces neuropeptide Y (NPY) activity in the hypothalamus.108 NPY is a powerful feeding stimulant in the nervous system, and researchers have found elevated levels of NPY in bulimics.109 Furthermore, Topamax suppresses the glutamate system—a system that stimulates appetite.110
It could be that by binge eating many times due to survival instincts, I conditioned a very strong appetite, mediated by NPY, the glutamate system, or another mechanism in my brain and nervous system. I simply made my body and brain physically dependent on excessive amounts of food. In this way, my binge-created brain-wiring problem resulted from strengthening neural pathways and affecting neurochemicals that supported this extreme appetite; and it is possible that Topamax temporarily tamed those pathways and neurochemicals.
A Habit of Pleasure
Another theorized mechanism through which Topamax works is by reducing the reward of binge eating.111 Binge eating is certainly motivated by the pleasurable properties of food, and like I said in the last chapter, highly palatable food is necessary for binge eating to occur. Topamax has been shown to reduce nicotine-induced increases of the pleasurable brain chemical dopamine in the brain of rats,112 and it could have a similar affect in reducing the pleasurable brain chemicals associated with binge eating, as well as other addictions.
As I've mentioned, the opioids—one class of pleasurable brain chemicals—are a possible culprit in the rewarding nature of binge eating.113 A history of caloric restriction can alter opioid-receptor function and make one more susceptible to binge eating.114 Then the rewarding properties of highly palatable food activate the altered opioid system, and binge eating can result.115 Further, eating foods high in carbohydrates increases serotonin, a neurotransmitter that produces feelings of relaxation and calmness, giving binge eating a soothing, mood-altering quality.116 Yet another feel-good brain chemical—dopamine—could be involved as well.117
Whether it's through opioids, dopamine, serotonin, or a combination of the three, binge eating activates a pleasure process in the brain and is therefore very rewarding to bulimics. Indeed, it's been shown that people with a high reward sensitivity—a biologically based personality trait that makes one more pleasure-seeking—have a higher risk of addiction and overeating.118 Maybe I found more pleasure in binge eating due to this trait; and by dieting and then binge eating over and over, I further heightened my reward sensitivity. In this way, I made my body and brain dependent on the temporary pleasurable effects of binges. My binge-created brain-wiring problem, then, was the sum of all my bungled but strong pleasure-seeking neural pathways. Topamax could have reduced the incentive value of binge eating by regulating those overactive pathways.
A Habit of Impulsivity
It's possible that my binge-created-brain-wiring problem was a habit of impulsivity. It's been shown that bulimics and those with BED are more impulsive, sometimes pathologically so
, and Topamax has been shown to decrease other impulsive behaviors besides binge eating.119 By succumbing to my survival drives over and over, I may have weakened the higher, rational parts of my brain responsible for voluntary action (at least when it came to binge eating) and strengthened those neural pathways responsible for the automatic behavior.
I could have been generally more impulsive even before my eating disorder began, which could explain why I had so much trouble resisting survival drives. Neuroscience research has shown that women with bulimia are less adept at self-control, even in tasks unrelated to eating.120 Women in one particular study did not engage circuits in the prefrontal cortex as effectively in a mental task as those without bulimia.121 Moreover, adolescents who have attention-deficit/hyperactivity disorder (ADHD)—a disorder characterized by impulsivity—are at greater risk for developing bulimia.122
It could be that I was already impulsive to begin with, and my repeated binge eating strengthened the neural pathways that supported my impulsive eating and weakened the neural pathways that could have allowed me to resist the urges. Thus my binge-created brain-wiring problem was the result of a weak will—not in a metaphorical sense, but a real neurologically based weakening of the parts of the brain that control voluntary actions. This does not mean I wasn't capable of resisting—I was simply out of practice and using the wrong tactics; but by succumbing over and over to my urges to binge, I only made it easier to keep giving in.
As I've said, I believe all three types of habits probably worked together to keep me binge eating. The habits of excess and pleasure fueled my urges, and the habit of impulsivity made me feel less capable of saying no, even though I certainly retained that ability. I always knew that I somehow had a choice of whether to binge or not, but I was usually not successful at exercising that choice. In the next chapter, I'll explain why I followed my urges to binge over and over again. But first, I need to address the fact that some people can and do develop a binge eating habit without ever dieting.
Brain Over Binge Page 14