Specific Knowledge:
Jotham Austin II, Ph.D. on Transformation

Calories In = Calories Out. In Fiction, the Math Doesn’t Work Out

While watching some of my favorite werewolf movies—An American Werewolf in London, Ginger Snaps, The Howling, Teen Wolf (hey, we all have guilty pleasures)—I started thinking. The most terrifying moment in horror isn’t the jump scare. It’s the transformation. Watching a human body betray itself, twist into something else. The human mind reduced to animal cravings. But something even more horrifying gnawed at me: The biology is all wrong. When did they eat?

“Dinner is in the oven…” – Fright Night (1985)

Horror and sci-fi love a good transformation. Human to beast. Loss of control. Giving in to the hunger… desire… lust…

The battle between the cerebral cortex—the center of our human control/sophistication—and that ancient reptilian part of our brain that drives our most basic impulses.

At least, that’s the story I tell myself after finishing a pint of Cherry Garcia while watching The Stuff.

Bad lizard brain!

But this isn’t about me. It’s about calories. So many tasty, metabolic calories in that pint of Cherry Garcia.

And you need a lot of calories to transform. Human to were-rabbit, fangless to full Count Dracula, dog to The Thing, mild-mannered scientist to gamma-powered Hulk.

Behind the spin-around dissolves, fades, legs extending from places they shouldn’t, and “you gotta be f’ing kidding me” reactions, there’s a biological math problem we rarely ask: Where does all this metabolic energy come from?

“Molecular decimation, breakdown and reformation is inherently purging. It makes a man a king!” – The Fly (1986)

Transformation is often a split-second visual effect. But it’s a complete physiological overhaul. If your cells are rearranging into claws, wings, or alien limbs, they need raw material, and more importantly, fuel. Calories. Lots of them. Enough to make even Joey Chestnut tap-out at an all-you-can-eat buffet.

This applies to all fictional shapeshifters. Mystique rebuilding her entire appearance? That’s not just changing pigmentation; it’s restructuring bone, muscle, and tissue. The Hulk gaining hundreds of pounds of muscle mass in seconds? The metabolic demand would be more than a plate of MCU superhero post-battle chicken shawarma.

Even vampires aren’t exempt. Drinking blood might seem efficient, but at only 650 calories per pint, Dracula would need to drain multiple victims (7,800 calories/person) just for one transformation.

“I cannot make you understand. I cannot make anyone understand what is happening inside me. I cannot even explain it to myself.” – Franz Kafka, The Metamorphosis (1915)

Metamorphosis is a slow, hungry business. The Oxford Dictionary defines it as a change in form or nature into something completely different, by natural or supernatural means.

In nature, true transformation takes time and fuel. When a caterpillar becomes a butterfly, it doesn’t shape-shift like a cartoon. It digests itself into goo, then rebuilds between 9 and 14 days using internal fat stores. No wonder that caterpillar was very hungry. Eric Carle got the science right.

During metamorphosis, metabolism spikes. Tadpoles becoming frogs see their oxygen consumption increase by 300–500%. In other words: transformation burns fuel. And lots of it.

Let’s consider another real-life transformation for perspective. Pregnancy: growing a 6–10 pound human requires approximately 300–500 extra calories per day for roughly 26 weeks. That’s 63,000–91,000 calories total. Luckily spread over the final six months of gradual development.

Want to transform in under 60 seconds? You’d need to consume calories like an Olympic athlete crossed with a competitive eater.

“I won’t be out late, so just wait for me. Don’t eat too fast.” – The Substance (2024)

Imagine you’re a werewolf. You go from human anatomy to full canine in under a minute. Hair, muscle, nails, bones, maybe a second set of teeth. What kind of Handwavium—a term for impossible science made possible through plot convenience—would that take?

A typical adult needs approximately 2,000–2,500 calories a day just to function. Not to grow a snout, claws, and a new skeleton. Transformation is anabolic: you need calories to form new cells, build tissues, organs, rewire neurons.

If you’ve ever tried gaining muscle, you know it takes an extra 2,500 calories per pound of new muscle. Now multiply that by supernatural speed and scale.

A werewolf shift might involve 20–30 pounds of added mass. That’s 50,000–75,000 calories. And that’s conservative, because the Second Law of Thermodynamics tells us no energy transfer is 100% efficient. Some energy is always lost as heat.

Stupid physics laws always getting in the way of my perfect plot. Cue the extra helping of Handwavium… I mean… You want fries with that?

“When the hunger hurts so much you’ve lost reason, then you’ll have to feed, and then you’ll need me to show you how.” – The Hunger (1983)

Eating that much is doable, theoretically. Elite athletes like Michael Phelps reportedly consumed up to 10,000 calories a day during peak training (though this figure has been disputed). Joey Chestnut? His record 76 hot dogs equals roughly 22,800 calories in ten minutes.

But here’s the kicker: you need calories to become the monster, and then even more to turn back.

A realistic transformation would require a three-phase meal plan:

  • Pre-transformation binge (one of everything, please): Be like a caterpillar. Store energy. Go into a food coma. I mean goo-cocoon.
  • Post-transformation devouring: Refill reserves. Waking up as a starving monster with poor communication skills and the lizard brain in full control? That’s how you get a horror movie.
  • Return to human: Need perfect balance of calories to make the return trip. The math here gets a little tricky because if you are going from muscular beast to average couch potato, you may need a deficiency of 3,500 calories to lose a pound. But remember that reptilian brain is in control now, and making this algebraic arithmetic mistake is how well-meaning friends doing a health check get eaten.

“Oh, lovely food! For rabbits that is!” – Wallace & Gromit: The Curse of the Were-Rabbit (2005)

And if you’ve ever wondered how many calories you’d get from eating a whole human? Wonder no more. A 150-pound person yields approximately 125,000 calories based on blood, muscle, and fat composition. That’s equivalent to 222 Big Macs. Or 122 pints of Cherry Garcia.

Yum.

Next time you watch a werewolf shift or a head stretch across a room, ask: When did they eat all those calories?

There should be burger wrappers, protein powder tubs, Costco meat pallets, and a food budget to rival an NFL offensive line. Transformation isn’t fast. Or cheap.

Find someone eating like that? You’ve found the monster. Because the real horror isn’t the claws or transformation. It’s the hunger.

“This is not magic, as you say. I am a scientist.” – Re-Animator (1985)

This gives new meaning to the lunar cycle in werewolf lore. It’s never been about moonlight, it’s about metabolic prep time. A month of all-you-can-eat-buffets to build the caloric reserves needed for transformation.

And in defense of werewolves, we should think about the struggles of Post-Transformation Calorie Deficiency (PTCD). They’re not killers. They’re just starving.

They need to eat before the change, and even more after. But without opposable thumbs to use a smartphone for DoorDash, it gets messy. Maybe it’s time for a PTCD awareness campaign. Feed a werewolf. Save a backpacker hiking the European countryside.

“Out by sixteen or dead on the scene, but together forever.” – Ginger Snaps (2000)

In the meantime, I’ll suspend disbelief and enjoy watching a socially awkward teen become a werewolf to discover his family secret, the meaning of friendship, self-confidence, and acceptance, as long as he wolfs-out and scores the winning basket.

But beyond the easy to digest plot, I still have questions about transformation time and conservation of mass (looking at you, vampires)…Well, that’s another rabbit hole entirely.

If you enjoyed this scientific deep-dive into fictional transformations, check out my podcast Rabbit Hole of Research, where my co-host and I explore more impossible science behind your favorite stories.

Jotham Austin, II, Ph.D. is a speculative fiction author and Research Associate Professor at The University of Chicago. With 29 years in cellular electron microscopy and over 24 peer-reviewed publications, his scientific expertise can be found in his storytelling.

His novel, Will You Still Love Me, If I Become Someone Else?, is a science fiction psychological thriller exploring memory, relationships, and identity. His horror short story “Lives Matter,” published in Red Line: Chicago Horror Stories, confronts generational trauma through a supernatural lens. He speaks publicly on science and genre fiction with talks like “The Cell Biology of Zombies” and has appeared on panels at Mars Con and Dragon Con.

If you enjoyed this essay’s scientific deep-dive into fictional transformations, check out Rabbit Hole of Research, the podcast he co-hosts where science meets fiction, pop culture—and “Handwavium” gets exposed.

More at jothamaustin.com