Into Thin Air

by Ellen Ruppel Shell

SEED Magazine | November 2003


For nearly a century, researchers have worked to unravel the riddles of anorexia, looking to psychology to provide the answers. Now an explosive new theory contends that the disease is a remnant of our food-deprived prehistory. If anorexia is, at least in some of us, innate, then the after-school specials have got it all wrong – and a paradigmatic shift may soon be underway.

Shan Guisinger’s paper, “Adapted to Flee Hypothesis,” makes the audacious claim that anorexia’s distinctive symptoms – food restriction, hyperactivity, and denial of starvation – are not mere psychopathologies but evolved adaptive mechanisms. That is, that anorexia is in a sense vestigial, a remnant of our food-deprived prehistory. Guisinger speculates that our ancient ancestors, nomadic foragers, stopped eating in order to migrate more efficiently in times of famine. Equipped with hunger-regulation circuits that urged them to drop everything and move on because other territories might have more food, their bodies effectively “turned down” hunger and “turned up” energy and optimism, to encourage them to travel great distances in pursuit of meat and forage. “Today, genetically susceptible people who lose a good deal of weight may trigger this archaic adaptation,” Guisinger says. “And that’s what underlies their illness.”

This theory is not only radical, it is explosive. For starters, it goes against everything we think we know about natural selection: How can a condition that kills you or, at best, makes you infertile, be adaptive? Why would an animal ever be equipped by evolution with a circuit that caused it to avoid eating food – especially when starving? But the Adapted to Flee hypothesis does not argue that anorexia helps an individual survive and reproduce in the modern world. Rather, it contends that anorexics experience a perversion of the innate mechanisms that kept their ancient ancestors alive.

Surely, the characteristics associated with anorexia – perfectionism, obsessiveness, and compulsivity – would have come in handy in prehistoric times. The ability to perform at high levels on low rations would almost certainly have conferred an evolutionary advantage on some hunter-gatherers, endowing them with the will to keep hunting and gathering when others had given up hope. “When resources were depleted and the tribe despaired, an anorexic’s energy, optimism, and grandiosity could mobilize the other members to heroic marches, much as Joan of Arc, an apparently anorexic peasant girl, inspired soldiers to march with her,” Guisinger writes in a draft of the Psychological Review paper. “When a starving tribe reached a new hunting-gathering ground, social pressure exerted by family and friends would in turn have helped anorexic member(s) to begin eating again.”

“In trying to explain anorexia, we have put a psychological overlay on what is essentially a physiological phenomenon,” Guisinger says. “Psychological factors are important, but we’re so in our heads that we sometimes forget that we have bodies.” The baffling behavior of people with anorexia, Guisinger says, becomes understandable when considered in the context of a complex set of adaptations selected in the prehistoric past – and played out every day in the barnyard. It’s all there, she says, if only we’d have a look.

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Thin Theory

by Maia Szalavitz

ELLE Magazine | June, 2004

Is anorexia all in its sufferers’ heads? One psychologist theorizes that it may be an ancient survival instinct gone awry in our modern culture of plenty.

For years we’ve been fed psychological theories about anorexia: It’s a hunger strike against controlling parents; it’s the ultimate capitulation to cultural commandments to be thin; it’s a disease of perfectionism abetted by unattainable images of whippet-thin models. But a new theory about the disorder suggests it may be biological, a remnant of evolutionary history that helped some women flee famine.

Shan Guisinger, PhD, a Montana psychologist, recently published this hypothesis in the journal Psychological Review after noticing that many anorexics – 90 percent of whom are female – desperately wanted to recover, despite the clinical definition of the disorder as a “refusal” to maintain a healthy body weight. “It felt biological to me,” she says. Guisinger, who has a master’s degree in zoology from Colorado State University, considered whether there could be an environment in which it made sense for a starving animal not to eat. She found that many animals stop eating to focus on a more important task – be it incubating, migrating, or defending a harem – despite extreme weight loss. Also, research shows that if rats are forced to lose 30 percent of their normal weight, they will run frantically on an exercise wheel and ignore food. Intriguingly, this phenomenon develops faster in female animals.

Unlike involuntary starvation, anorexia leads to periods of hyperactivity, Guisinger says, accompanied by a feeling of being on a mission: “There is this sense of superiority, of virtue – a humorless quality.” In her paper, she describes how such a mechanism could enable women to escape death, giving them the energy and tenacity to travel beyond the famine-stricken region. When a woman reached a food-rich region, she would become hungry, settle, and eat.

As for why today’s anorexics don’t recommence eating, Guisinger says that while they do tend to lose their appetite for much of their illness, they often experience a period of great hunger, typically late in recovery. But because our culture has made them so frightened of becoming fat, rather than yield they often redouble their dieting and exercise. She also accounts for why women would suffer from the disorder disproportionately: Men wouldn’t benefit as much from a famine-flight strategy. In nature, males who try to enter the territories of others are attacked, while females are usually welcomed.

Guisinger’s theory is bolstered by other research. Studies now find that anorexia is, at least in part, genetic, with identical twins much more likely to share the condition than fraternals. There is also evidence than anorexics have conflicting levels of appetite-regulating substances in their brains and stomachs. Their brains’ levels of the neurotransmitters serotonin, dopamine, and norepinephrine are the opposite of what they should be to signal a craving for food. At the same time, their stomachs send out mixed messages, retelling the brain they are full and hungry simultaneously. Essentially, “this means that the person with anorexia is tormented by desire for food she cannot bring herself to eat,” Guisinger says. This odd chemical imbalance could be the biological signature of a need to seek food but not eat it.

In industrialized nations, only compulsively driven perfectionists and those with wasting illnesses would be able to starve enough to activate this mechanism in the first place. And indeed, anorexia sometimes starts when another disease causes dramatic weight loss, Guisinger says.

Her theory suggests that current treatments focused on perfectionism or family dysfunction are misguided. Perfectionism may start the disease process, but then biology takes over. Research shows that one new therapy that’s been proven effective teaches those closest to the anorexic to help her to eat – even in adult anorexics, this is usually the mother – and it’s easier to engage mothers in therapy that doesn’t blame them. “Theories on schizophrenia once blamed the ‘schizophrenogenic’ mother….With anorexia, controlling mothers are still the culprit,” says Guisinger, who hopes her ideas will end this view.

But the eating disorder-treatment community – many of whom have spent years working on the assumptions of the perfectionism theory – has responded coolly. William Davis, PhD, the vice president of research and program development of the respected Renfrew Center for eating-disorder treatment, agrees that anorexia is not caused by intrusive parents but thinks that Guisinger’s theory is “irrelevant to clinical practice – it has nothing to do with an anorexic’s experience of herself.”

Research academics in the field, however, are more supportive. “It’s a plausible hypothesis,” says Janet Treasure, PhD, the director of the Eating Disorders Unit at London’s Maudsley Hospital. Evolutionary psychologist Debra Lieberman, PhD, of the University of Hawaii is skeptical but says, “It’s wonderful we’re starting to think about these disorders in an evolutionary light.”

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The Globe and Mail

A disease to fight famine?

by Stephen Strauss

The Globe & Mail, Page F8 | January 17, 2004

Feeling hungry, but aren’t tempted to eat? Want instead to start running and keep chugging as long as you can?

In humanity’s hungry past, these twinned responses might have been a vital survival instinct for someone needing the strength to flee from famine. But today the same body response might be anorexia nervosa.

This is the radical thesis that evolutionary psychologist Shan Guisinger put forward in a paper recently published in the journal Psychological Review. She describes the failures of psychological and social theories to explain the reason anorexia strikes so many more women than men – a ratio of 10 to 1 is often cited – and the condition’s strange features.

“Normal” starvation leads to lethargy, depression and increased hunger. Anorexia leads to food refusal, optimism and hyperactivity. Dr. Guisinger argues that the most likely explanation for this is that the genetics of a certain subset of the female population allowed them to lead their families through hungry times.

“When resources were depleted and the tribe despaired, the anorectic’s energy, optimism and grandiosity would mobilize the other members to heroic marches. . . . When a starving tribe reached a new hunting/gathering ground, social pressure exerted by family and friends would in turn have helped the anorectic member(s) to begin eating again,” she says.

Over time, evolution would have favoured women carrying genes for famine-fighting anorexia.

To support her thesis, Dr. Guisinger presents a host of human, animal, biochemical and historical evidence, but she concludes with a caution: “Like obesity, AN was useful then and is deadly now.”

While clearly not the final word on a complicated subject, her analysis allows one to understand the roots of a condition so widespread that common sense says it must have served some larger good in the human evolutionary past.

Find a copy of the article here.

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The Boston Globe

The Ancestry of Anorexia
Blame biology, not parenting, new theory suggests

by Ellen Ruppel Shell

The Boston Globe | December 30, 2003


Anorexia, the most lethal of psychiatric disorders, afflicts as many as 1 percent of young women and about a tenth as many men, and casts a Svengalian spell, leading its victims to willingly starve themselves in the midst of plenty. Now, psychologist Shan Guisinger has developed a radical new view of anorexia that she says explains both the bizarre features of the illness — self starvation and hyperactivity — and its resistance to treatment by traditional psychotherapy.

Anorexia, she contends, is not primarily a psychological condition brought on by a troubled childhood — as is often thought — but a disorder based in biology, specifically in the appetite regulation mechanism in the brain. Her theory postulates that anorexics have a biological adaptation to weight loss that causes their bodies to shut off hunger signals, and to ratchet up physical activity, even as their flesh melts away.

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SELF Magazine

No time to lose

by Ginny Graves

SELF Magazine | January 22, 2007


Even the urge to overexercise can be the result of a chronic lack of food. Studies show that if rats are starved and then maintained at 70 percent of their normal weight, they’ll run up to 20 kilometers a day, says Shan Guisinger, Ph.D., an eating disorders specialist in Missoula, Montana. She believes the manic exercise often seen in patients is an adaptation to famine. “In prehistoric times, when there wasn’t enough food, women had to travel hundreds of miles to find more, so they needed to be able to walk for hours with little to eat,” she says. “When women starve themselves, that hardwired restlessness may kick in.”

Find a copy of the article here.

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Monitor on Psychology

An evolutionary explanation for anorexia?

by Karen Kersting

Monitor, Vol. 35, No. 4, page 22 | April 2004

Modern anorexia may stem from an adaptation that helped ancient nomadic people find food, according to a recently proposed theory.

An evolutionary instinct that told members of migrating populations to move along when their food supply ran out may be a major contributor to modern anorexia nervosa, according to a new theory.

When food is scarce and starvation begins, most animals and people demonstrate intense hunger, low activity levels and a single-minded search for food. But, when starved, individuals with a genetic tendency toward anorexia feel sated, full of energy and unfazed by starvation–a set of symptoms described in the DSM-IV, says psychologist and Missoula, Mont. private practitioner Shan Guisinger, PhD, in an article published last year in Psychological Review (Vol. 110, No. 4).

“In treating anorexics, I started to wonder if their symptoms could be something that was useful in the past,” Guisinger explains. “When nomadic foragers were starving, it wouldn’t make sense to hunker down and just not eat. If you’re starving it means that there’s no food there, and so you should move on–normal adaptations to starvation would get in the way.”

A problematic adaptation

In the nomadic groups that preceded modern civilization, members who were undeterred by hunger may have become leaders and moved the group to places where food was plentiful, Guisinger says. She argues that this ancient adaptation, which was likely an advantage at the time, today continues to cause anorexia in people who have a genetic predisposition to it.

But whereas food scarcity may have been the original catalyst for anorexia–which kicks in when genetically susceptible people lose 15 percent of their normal body weight through lack of food–intentional dieting related to societal fear of being fat is most often the cause in modern cases, Guisinger says.

“A lot of people have trouble with this theory because they think now, in modern times, when there’s so much food around, why don’t anorexics just start eating again?” she notes. “But the thing about the brain is that it simply responds to body fat levels, making automatic adjustments to hunger and satiety signalers. Evolution is not very elegant sometimes, and adaptations persist where they are not needed. In this case, the adaptation turns off hunger in modern women who diet.”

Making the case through research

Guisinger backs up her theory with evidence from myriad studies pieced together to show that the core symptoms of the disease make adaptive sense. For example, she references research by psychologists Nicholas Mrosovsky, PhD, and David F. Sherry, PhD, that describes food-restriction behavior across species when animals must migrate.

She also cites research by Leo Kron, MD, that illustrates anorexic patients’ tendency toward hyperactivity and compulsions to move. And she points to research by historian Rudolph Bell, PhD, that documents anorexia in medieval people who lost weight through religious fasting. They, too, demonstrated distorted body images, hyperactivity and food refusal.

Though Guisinger’s theory is carefully constructed through her presentation of such evidence, proving an evolutionary cause for a modern illness is tricky, says psychologist Jeanine Cogan, PhD, founder of the Eating Disorders Coalition for Research, Policy and Action. Because Guisinger is looking to the past for causation, proving her hypothesis through research is impossible, she adds.

“She’s made an interpretation that’s compelling,” Cogan says. “And what I found most useful is she raised some excellent points about the physiological and psychological effects of food restriction that may play an important role in causing anorexia.”

Guisinger, who has never published a research article on anorexia before, says she came to her evolutionary conclusion after years of observing patients who wanted to eat, but claimed to be stopped by their bodies. Now, she says the most important step in helping patients is getting their weight back to normal, which, she believes, will turn off their genetically programmed anorexic response. The hypothesis can serve as a basis for cognitive behavioral therapy and for enlisting the aid of loved ones to help keep body weight up, she adds.

“It doesn’t make psychotherapy irrelevant, but it means that more than anything, people are going to need all the help they can get from their therapist, family, doctor and dietician to fight against their body’s signals in, what is to them, a very unnatural way,” she says.

Find a copy of the article here.

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