Many animals get anorexia, helping explain why anorexia is an evolutionary adaptation

Video transcript of:

Today, I'll be taking you on a world tour and talking about lots of animals. This will be a fun ride!

Hi, I'm Michelle Cen. I recovered from 5 years of anorexia and bulimia thanks to learning about the work of Dr. Shan Guisinger.

Dr. Guisinger is a clinical psychologist and evolutionary biologist. She's treated eating disorders for over 30 years using her Adapted to Flee Famine theory. I'll explain her theory today, focusing on how evidence of anorexia in many animals helps prove it's an adaptive device in humans too.

Learning this evolutionary theory helps anorexics recover. They won't be able to resist their disordered thoughts until they truly, 100% believe the thoughts are irrational.

As neurobiology professor Andrew Huberman explains, knowledge of knowledge allows you to make better decisions. Knowledge leads to neuroplasticity. Neuroplasticity is your brain's ability to rewire synaptic connections, which changes your habitual thoughts.

Basically, you can improve your brain, changing it from an anorexic one to a healthy one.

By learning the evolutionary science behind anorexia, I finally saw just how absurd my anorexic brain's thoughts were for the modern-day environment I live in. If you have an eating disorder, I know you can reclaim your mind and recover too.

Today, I'll be taking you on a world tour and talking about lots of animals. This will be a fun ride!

We're looking at the ocean right now. In some months you'll be able to spot gray whales. Every year, gray whales perform one of the longest migrations of any mammal. They travel 12,000 miles round-trip, leaving their food sources in the Arctic to go breed in Baja California. They lose 15-30 percent of their body weight during this journey. Just like migrating sea turtles, they ignore food in the water they're swimming through.

So gray whales ignore food, ignore fatigue, and are hyperactive. These are all of anorexia's symptoms. Basically, gray whales become anorexic.

A lot of animals become anorexic in some situations, actually.

Let's play a game, what do you think these 5 species all do in the following situations?

Green turtles migrating to nesting beaches... Male elephant seals defending their territories and taking care of their young... Polar bear mothers nursing their cubs in caves for months... Red deer in mating season.... Birds incubating eggs...

You might have guessed it. That's right, these animals all stop eating. They all lose lots of body weight in their quest to reproduce.

For instance, male penguins don't eat for months while breeding. They'll lose up to 40% of their weight as they nest in a colony.

Those species provide solid evidence that anorexia is an adaptive migratory mechanism.

Thousands of years ago during the Pleistocene, also known as the Ice Age, humans were opportunistic foragers and hunter-gatherers. By looking at species which are also opportunistic wandering foragers, we find even more evidence of anorexia as an adaptive mechanism to flee famine.

Rats, mice and pigs also become anorexic when they must find food. Evolutionary biologists have observed for decades how these species eat less when traveling. It's probably so they can migrate more efficiently to better land.

Unfortunately, in unnatural modern environments, these instincts can lead to animals perishing. In 1954, learning psychologists starved rats, then gave them food. To their surprise, starving rats ignored the food and ran themselves to death on their wheels. Rats typically run less than 1 km per day, but when starved they run up to 20 km per day.

So paradoxically, as their weight drops, they exercise more.

This finding is so counterintuitive that I'll repeat it. Rats who initially were under food restriction, but then get unrestricted food access, will ignore the food and literally run to death.

Biologists already figured out the behavior of rats was because of their fleeing famine instinct. In the artificial lab environment, their running on wheels doesn't get them anywhere so they die. But if these rats were in the wild, their running would have given them a chance to find better lands.

Pigs will also spontaneously stop eating and start moving when they're starved. It's known as "wasting pig syndrome" or "thin sow syndrome," and its clinical features are exactly like how anorexia manifests in humans. The pigs will stop eating their high fat feed, and instead eat low-calorie straw. It's just like how anorexic humans will snack on vegetables and detest high-calorie fat.

Brain imaging studies have showed that the right amygdala of the brain, which is responsible for conditioned fear, is overactive in anorexics when they're asked to imagine eating. Anorexics also have low galanin levels, the hormone that signals desire for fat.

The anorexic dislike of fat likely allowed pigs, humans, and other animals to travel more efficiently in their past. Here's Dr. Guisinger's theory as to why:

In omnivorous hunter gatherer diets, animals are the primary fat source. Studies of hunter gatherers have shown that when food was scarce, the hunter gatherers mostly ate plants, like tubers and berries, rather than hunted animals. Disliking fat may have helped them acquire food more effectively by gathering plants instead of hunting animals.

As you can imagine, hunting animals was much more difficult, exhausting, and time-consuming than picking plants. Plants may also be less likely to harm or kill you.

It's only natural to apply this anorexic instinct, found in so many animals, to humans too. Anorexic humans are like the rats running on the wheel, ignoring food and unwittingly hurting themselves. Anorexic humans are like the pigs who eat straw and ignore their high fat feed, even when starving to death.

When explicated by Dr. Guisinger's Adapted to Flee Famine theory, anorexia's seemingly baffling symptoms now make sense.

During a famine, ancestors in the Pleistocene could either wait it out or search for better lands. The ones better at ignoring their hunger and fatigue were the ones who successfully migrated out and survived. These were the anorexics.

Anorexia was a useful short-term adaptation for migrating hunter gatherers. Now anorexia, manifesting in a modern-day environment with less famine, causes a terrible fear of fat and food. We need fat to survive, and I'll explain its importance in a future video.

I'll also explain in future videos more science validating the Adapted to Famine theory. The evolutionary theory demystifies observations that have previously confounded others. Phenomena such as why Africans have the lowest anorexia rates and Native Americans have the highest, or why reproductive-age females are most likely to have anorexia.

The takeaway from today's video is that plenty of animals have anorexia as an adaptive mechanism, and thus it's likely an adaptive mechanism in humans too. Knowing this helps anorexia sufferers feel more kind toward their own body's natural evolutionary adaptations and feel comfortable in ignoring their compulsive desires to not eat and to exercise too much.

I love animals and don't eat them partly because of that. I respect your choices too, this is just my ethical decision. As I'll explain in another video, I actually regained weight twice as fast as a vegan than an omnivore. Definitely you can recover from eating disorders eating animals or not, I just want to make the point that you can recover as a vegan.

You can recover. You can heal your mind and body.

If you want to find out more about Dr. Guisinger's work, visit her website at ( She's releasing a book on Adapted to Famine to be published by the American Psychological Association Press. It's an eating disorder treatment manual that I know will improve the way we treat patients.

If you want to learn more about me, just go to my website ( That's Michelle C-E-N dot com. For more about my own eating disorder recovery and an overview of the Adapted to Famine theory, go to this video linked here and below.

Thanks for watching and take care. I'm going to go eat now because I'm hungry.