10 Smackdowns That Lay Waste to CICO

Gaze upon these arguments, ye mighty gym bros, and despair...

It’s time to torch what’s easily the dumbest idea in the entire universe—the “calories in, calories out” model of obesity, affectionately known as CICO. Basically, it’s the concept that, if you get fat, it’s your fault—a punishment for your sins of gluttony and sloth—and that only the moral path of restraint and industriousness leads to leanness.

I call CICO the “Banker” model, in that it imagines the fat tissue as like a bank vault for excess calories. (This is, of course, beyond inane.) Plenty of sharp thinkers have also ripped CICO apart, but their insights are scattered across the wilds of the World Wide Web. As with anything in life, focus is power. The sun’s light can be concentrated into a fire with a magnifying glass.

This post is that magnifying glass.

A Few Notes Before We Begin

1. Most of the anti-CICO crowd is also pro-low-carb, keto, or fasting. Why? When you strip away the simplistic calorie math and look at what actually controls fat storage, insulin stands out as the 800-pound gorilla. And what drives insulin? Carbohydrates (hence keto). Meal timing also plays a huge role (hence fasting).

   Also, thought influences thought. We read each other’s work, build on it, and refine our understanding. That said, the Farmer Model (a.k.a. “the fuel-partitioning model of obesity” is NOT the same as the carbs-insulin model. You can be a vegan Star McDougaller or eat whatever you damn please and still be pro-Farmer.)

2. We’ll deal with the CICO diehards another time. You know the type. They’ve seen the anti-CICO evidence, but they refuse to engage with it in good faith. Some just hate keto (for “reasons”). Some—looking at you, Kevin Hall—are professionally invested in defending CICO. Others are metabolically gifted types, who were born on third base and think they hit a triple. These people have a reading comprehension problem and can’t seem to understand our arguments. Their responses read like rageful Boomer Facebook rants, written IN ALL CAPS TO SHUT DOWN CONVERSATION. As I’ve mentioned before, I once corresponded with a famous pro-CICO doctor. I sent her evidence of rats that starved to death while still obese. Her response? "I am not skeptical of calories in, calories out, because I’ve seen it work for my dog." Take that mindset, fuel it with Monster energy and gym bro steroids, and you have the full CICO playbook.

Let’s get rolling!

1. Gary Taubes’ “Laws of Adiposity”

Of course, we have to kick this off with the big dog himself: science journalist Gary Taubes. He’s the most influential voice in this debate, and almost certainly the intellectual ancestor of many of the thinkers below.

Taubes lays out three fundamental laws of adiposity that gut the CICO model:

1. First Law: “Body fat is carefully regulated, if not exquisitely so... The evidence that fat tissue is carefully regulated, not just a garbage can where we dump whatever calories we don’t burn, is incontrovertible.”

2. Second Law: “Obesity can be caused by a regulatory defect so small that it would be undetectable by any technique yet invented.”

3. Third Law: “Whatever makes us both fatter and heavier will also make us overeat.”

The Squirrels Prove the Point

We regulate fat biologically, just like every other species. The idea that humans uniquely fail to regulate their fat stores, while every other mammal on Earth does so effortlessly, is insane. Per Taubes:

Excellent examples of how carefully animals (and so presumably humans, too) regulate their fat accumulation are hibernating rodents -- ground squirrels, for example, which double their weight and body fat in just a few weeks of late summer. Dissecting these squirrels at their peak weight, as one researcher described it to me, is like “opening a can of Crisco oil -- enormous gobs of fat, all over the place.”

But these squirrels will accumulate this fat regardless of how much they eat, just like Wade’s ovary-less rats. They can be housed in a laboratory and kept to a strict diet from springtime, when they awake from hibernation, through late summer and they’ll get just as fat as squirrels allowed to eat to their heart’s content. They’ll burn the fat through the winter and lose it at the same rate, whether they remain awake in a warm laboratory with food available, or go into full hibernation, eating not a bite and surviving solely off their fat supplies.

The fact is there’s very few things that researchers can do to keep these animals from gaining and losing fat on schedule. Manipulating the food available, short of starving them to death, is not one of them. The amount of fat on these rodents at any particular time of the year is regulated entirely by biological factors, not the food available or the amount of energy required to get that food. And this makes perfect sense. If an animal that requires enormous gobs of fat for its winter fuel supply were to require excessive amounts of food to accumulate that fat, then one bad summer would have long ago wiped out the entire species.

It may be true that evolution has singled out humans as the sole species on the planet that does not work to carefully regulate its fat stores in response to periods of both feast and famine, that some people will stockpile so much fat merely because food is available in abundance that they become virtually immobile; but it requires that we ignore virtually everything we know about evolution to accept this conclusion.

2. Peter at Hyperlipid’s Paradoxical Fat Mice

Even if you’ve been around the keto/low-carb world for years, you might not have stumbled across Hyperlipid, the blog of Peter Dobromylskyj. He’s a vet physiologist, but more importantly, he’s a mad scientist-level genius when it comes to metabolic physiology. His writing isn’t for the casual reader—it’s dense, technical, and loaded with insights that even researchers study on their off-hours.

His legendary protons series is on my must-read list, but I’ll be honest—even skimming it kind of makes my head explode.

In one deep dive, Peter breaks down a metabolic paradox. Researchers genetically modified mice to produce less insulin, then placed them on a 40% caloric restriction (CR) diet. If CICO were true, they should have lost fat. Instead? They became fatter than their unrestricted counterparts—despite eating less.

These mice became so efficient at pulling nutrients into storage that their bodies locked calories away in fat cells almost immediately after eating. Their bodies reacted by entering torpor—a hypothermic, low-energy state designed to conserve fuel.

Peter explains:

I think torpor happens because the mice simply have no accessible calories. This is despite the fact that it occurs immediately after the third of their calorie-restricted meals. Their problem is that the meals generate an insulin response. The mice are so insulin sensitive that calories are lost into adipocytes (and probably hepatocytes) under the over-effective action of insulin. They lose calories into adipocytes. These are calories out. The adipocytes get bigger with the lost fat. Torpor occurs BECAUSE the mice have become fatter. This is the equivalent of the hunger which follows for a human under a euglycaemic (or even hyperglycaemic) hyperinsulinaemic clamp. There is no hypoglycaemia but fatty acids become locked into adipocytes by the hyperisulinaemia and hunger follows due to a lack of available calories.

Translation? These mice were starving in the midst of plenty. Their bodies weren’t suffering from a calorie deficit—they were suffering from a fuel-partitioning defect.

3. Mark Friedman et al: Time to Leave Energy Balance Behind

Mark Friedman is a lion in this field—one of the most sophisticated anti-CICO thinkers alongside Gary Taubes. His 1976 paper, The Physiological Psychology of Hunger: A Physiological Perspective, was lightyears ahead of its time. While the mainstream still fixates on obesity as an “overeating disorder,” Friedman recognized it even half a century ago as a problem of fuel partitioning.

Fast forward a few decades, and Friedman is still dismantling the CICO model. In a rejoinder to Kevin Hall, in the American Journal of Clinical Nutrition, he writes:

Partitioning of fuels among different tissues and cellular metabolic pathways is essential to maintain an adequate supply of energy and sustain life. A variety of neural and endocrine mechanisms control these fluxes of energy-yielding substrate. Many of the short- and long-term signaling mechanisms for eating behavior mentioned by Hall et al. affect fuel partitioning or metabolism independent of their effects on food intake, raising the possibility that it is these physiologic effects that indirectly drive changes in intake.

Given the emphasis on the role of the brain in their model of food intake—and, of course, any model of food intake must include the brain—it is worth noting that experimental manipulation of central neurons or neuronal circuits believed to control eating behavior also affects peripheral fuel partitioning independent of changes in intake.

For example, inhibition of the central melanocortin system, thought to be involved in human obesity, shifts fuel partitioning toward fat accumulation independent of the increased intake it provokes in ad libitum fed animals and with no apparent change in energy expenditure or physical activity. The issue of direct and indirect effects of neural interventions on eating behavior is not new and harkens back at least to the very first widely studied animal model of obesity, rats with ventromedial hypothalamic lesions. Experimental treatments could certainly modify eating behavior directly by activating or inhibiting neural circuits that specifically control intake. However, until we can sort out whether the behavioral response is the report or echo from such treatments, we risk being misled in the hunt for mechanisms controlling both food intake and fat accumulation.

This seems exactly right. I would go as far as to say that this is being overly charitable, in that it is very clearly impossible for the Hall/CICO framework to make heads or tails of what happened with the VMH rats—and similarly paradoxical rodents.

4. Dr. Michael Eades’ Third Alternative

Dr. Michael Eades is a best-selling author (Protein Power, The Protein Power Lifeplan, The Arrow), long-time advocate of low carb, and sharp critic of mainstream diet dogma. He’s close friends with Gary Taubes, sharing his skepticism toward CICO.

In a 2023 talk at Low Carb Down Under called “Weight Loss: Calories, Insulin, or a Third Alternative?” he explains that the body doesn’t store or excrete “calories.” It stores and loses mass—primarily in the form of fat, water, and CO₂. When fat burns, 84% exits the body as CO₂ and 16% as water. Meanwhile, heat—what calorie obsessives focus on—has no mass. If the CICO framework were valid, you should be able to lose weight just by “burning calories.” But you can’t, because weight loss only happens when atoms physically leave your body.

Dr. Eades explains:

Think about the mass balance equation: Δmass = mass in - mass out. If you want to change your mass in a downward direction, you’ve got to either decrease the mass coming in or increase the mass going out. Preferably both to maximize weight loss. So, if you eat less food, you take in less mass. That’s part one. If you exercise (move more), you’ll burn more fat and breathe harder, which will remove more CO2 and H2O than if you were just sitting watching TV. Makes sense, right? But we all know from experience that if we eat less and move more, we get hungry. And hunger can be held at bay for a while, but it is such a strong survival urge that we ultimately succumb. Which is why Eat Less, Move More has become kind of a joke in the weight loss community. It just doesn’t work.

5. J. Stanton’s “No Such Thing as a Calorie to Your Body” Rant

J. Stanton, writing at gnolls.org, was one of the sharper voices in the early days of the low-carb, anti-CICO movement. His article, No Such Thing as a Calorie to Your Body, dismantles the idea that food should be measured—or even thought about—in terms of calories. He argues: “The concept of the ‘calorie,’ as applied to nutrition, is an oversimplification so extreme as to be untrue in practice.”

Our bodies are not steam engines. We don’t “burn” food the way a combustion chamber does, nor do we convert food directly into mechanical work by measuring its heat output. There is no biochemical system in the body whose input is a ‘calorie.’ Instead, food has many fates. It can be used to build and repair tissue—muscle, skin, nerves, bones. It fuels the production of enzymes, hormones, and other critical molecules that keep everything running. Some of it goes toward producing digestive fluids, like bile and stomach acid, or feeding our gut bacteria, which, in turn, create metabolic byproducts that our bodies repurpose. Some food simply passes through and is excreted unused. And, of course, excess can be stored as glycogen or fat.

The key insight? Only one of these processes—immediate conversion to energy—aligns with the simplistic calorie model. The rest have nothing to do with “burning calories.” So when CICO believers reduce food to a simple “calories in, calories out” equation, they’re missing the entire complexity of human metabolism.

6. Feinman and Fine: The CICO Model Violates the 2nd Law of Thermodynamics

Richard Feinman and Eugene Fine are heavyweights in the nutrition world. Back when I first started writing about this stuff, Richard generously invited me to a meeting of his Nutrition and Metabolism Society, where I met many big names in keto—including Dr. Richard Bernstein, a legend in diabetes research, and Fred Hahn, the mastermind behind Slow Burn Fitness. (Side note: Hahn’s high-intensity training methods are gospel to me. I will preach them to anyone who will listen.)

But I digress.

Feinman and Fine’s attack on CICO comes not from biochemistry but from physics—specifically, the Second Law of Thermodynamics. This law states that in any closed system, energy transformations increase entropy (disorder). The problem? CICO treats the human body like a bomb calorimeter—a dumb, passive system where “calories in” minus “calories out” determines weight gain or loss. But the human body is NOT a closed system. It actively regulates energy balance through enzymes, hormones, and metabolic pathways. Their critique echoes Stanton’s: CICO assumes that all calories are metabolized identically, no matter the source. This is demonstrably false. Different macronutrients take different metabolic paths, with wildly different efficiencies.

7. David Ludwig - Rethinking the Reasons We’re Always Hungry

Harvard researcher David Ludwig is one of the leading voices behind the Carbohydrate-Insulin Model (CIM). He’s the author of Always Hungry and has spent years dismantling CICO thinking in both research and public discussions. Years ago, I had him on my (short-lived) podcast, where we explored these ideas in depth. In a New York Times interview, Ludwig provides a direct critique of the CICO model:

We think of obesity as a state of excess, but it’s really more akin to a state of starvation. If the fat cells are storing too many calories, the brain doesn’t have access to enough to make sure that metabolism runs properly. So the brain makes us hungry in an attempt to solve that problem, and we overeat and feel better temporarily. But if the fat cells continue to take in too many calories, then we get stuck in this never-ending cycle of overeating and weight gain. The problem isn’t that there are too many calories in the fat cells, it’s that there’s too few in the bloodstream, and cutting back on calories can’t work… An analogy would be like trying to treat a fever with an ice bath. Imagine going to the hospital with a very high fever, and the doctor says, “Fever is just a problem of heat balance – too much heat in the body, not enough heat leaving the body.” That’s true from a physics standpoint. So the doctor decides to put you in an ice bath. That will work temporarily. An ice bath will break your fever. But imagine what’s going to happen. Your body is going to fight back furiously with severe shivering and blood vessel constriction and you’ll feel miserable. You’ll want out of that ice bath as soon as possible. For that reason, ice baths are not a popular treatment for fever… A much more effective approach is to lower the body’s temperature set point, which is done with medicine like aspirin. Put biology on your side by eating the right way, and weight loss occurs naturally as a fever would break if you treat the underlying cause of the fever.

8. Tom Naughton - The Clogged Pipes Analogy

Tom Naughton, a comedian-turned-nutrition-science renegade, became a well-known voice in the low-carb community with his 2009 documentary, Fathead. The film was a direct rebuttal to Supersize Me, in which Morgan Spurlock blamed fast food—especially fat—for his weight gain and declining health after a month-long McDonald’s binge. Naughton conducted his own version of the experiment but kept carbs low—and instead of gaining weight and wrecking his health, he lost weight and improved his metabolic markers.

In one blog post (from ages ago) Naughton took a humorous scalpel to CICO:

Arguing about whether weight gain/loss is caused by the hormonal effects of diet or CICO is like arguing whether your toilet overflowed because of a clog in the pipe or because more water went into the toilet than went out. CICO always applies, but that’s the HOW of the result, not the WHY.

I’m not sure why this is such a difficult concept for some people to wrap their brains around, but apparently it is. So I’ll try to explain one more time:

Those of us who believe losing weight isn’t as simple as restricting calories aren’t denying the laws of physics. People have accused Gary Taubes of ignoring the laws of thermodynamics, but frankly, that’s beyond ridiculous. The man has a degree in physics from Harvard, for pete’s sake. His first award-winning book was about physics. It seems rather unlikely that when he wrote Good Calories, Bad Calories, he just up and decided the laws of physics don’t apply to obesity or weight loss.

What he’s tried to explain in at least a couple of speeches I watched online is that yes, of course, if you increase your body mass, you consumed more calories than you expended. If you decrease your body mass, then yes, of course, you expended more calories than you consumed. But that’s all the calories-in/calories-out equation can tell us. It doesn’t tell us the actual reason weight gain or weight loss occurred.

As I was trying to get across in my Facebook comment, we’re talking about the difference between HOW vs. WHY. If my toilet overflows, then yes, more water entered the bowl than exited. That’s HOW it overflowed. But that’s not WHY it overflowed. The WHY would have something to do with a clog in the pipes.

9. Dr. Jason Fung: The First Law of Thermodynamics is Utterly Irrelevant

CICO people love to scream “THERMODYNAMICS!” like it’s a magic spell. But what if thermodynamics has nothing to do with human metabolism? Enter Dr. Jason Fung, a nephrologist and leading voice in the fasting and low-carb community. His perspective on weight loss is refreshingly blunt:

[Calories are] simply irrelevant to human physiology. I studied biochemistry in university and took a full year course on thermodynamics. At no point did we ever discuss the human body or weight gain/ loss. Because it has nothing to do with thermodynamics. If anybody mentions the ‘first law of thermodynamics’ regarding weight loss, you, too will know that they are just not very smart. Or maybe they just haven’t really thought about what thermodynamics actually is.

Nutritionists on the other hand, especially the calorie counters, can’t seem to say enough about Thermodynamics. They have ‘science’ envy. They desperately want the quantitative and theoretical backing of hard science and therefore pretend that human physiology is like physics, with its hard rules and laws.

New flash, guys. Physiology is physiology and physics is physics. Don’t mess the two up. The CICO people are Fregley. He is the character in ‘Diary of a Wimpy Kid’ who is the unpopular kid who wants desperately to be liked. CICO people desperately want the approval of hard science that they are willing to pretend that physiology is physics. Sorry buddy. Just because you have physics envy, doesn’t mean you get to make up stuff…

The lunatics are running the asylum – and they all believe in the First Law of Thermodynamics. In discussing the physiology of obesity, the First Law of Thermodynamics is not wrong – it’s irrelevant.

10. ItsTheWoo – Are They So Rigid Minded and Dogmatic, Not Unlike a Cartoonish Villain Such as Javert?

I’m saving the best for last.

The anonymous blogger known as ItsTheWoo was a fiery voice in the nutrition science space, blending physiological insights with unapologetic snark. She was a nurse and someone who—like Hyperlipid—was obsessed with digging into the biochemical details that others overlooked. Her blog is now offline. Thankfully, I found one of her classic rants preserved in an online forum:

Ya know blog, I’m not sure if [the CICO advocates] are actually purposefully pretending to misunderstand the hormone hypothesis argument, or if they really are too stupid to understand it. I just can’t tell. In my view it is beyond evident physiological factors are responsible for fat mass gain; calories and the mechanisms to obtain them (sloth/gluttony) are merely reactive to the body state which is controlled by baseline physiology. So, when [the CICO advocates] for years and years and years keep writing mind numbingly stupid shit like this:

‘We again are asked to ignore the obvious — that Americans are definitely eating more, on average, with no concurrent need for those calories, and likely moving a bit less as well.’

I just don’t know what to think anymore. Are they morons? Are they so, so stupid they really can’t see the inverse projection of this system, which much more intelligent people have gone to great lengths to simplify and make child-friendly illustrations for them? Are they pretending not to understand because they have a vested interest in eating as much neurotransmitter plastering glucose/insulin whenever they want? Are they so rigid minded and dogmatic, not unlike a cartoonish villain such as Javert, that they can’t at all waver from their convictions no matter how ridiculous those convictions reveal themselves to be?

Bonus #1: Amy Berger – It’s the Insulin, Stupid

In It’s the Insulin, Stupid, Amy Berger dismantles the CICO myth by showing that fat storage is a hormonal issue, not a calorie-counting problem. If eating less and moving more actually worked, nobody would be overweight. But biology doesn’t play by CICO’s rules—hormones run the show.

Bonus #2: Tim Noakes – It’s the Insulin Resistance, Stupid

In It’s the Insulin Resistance, Stupid, a 3 part series—part one, part two, part three—South Africa’s Tim Noakes attacks CICO and shows how high-carb diets spike insulin, trapping fat in storage and making weight loss nearly impossible. Meanwhile, cutting carbs lowers insulin, unlocks fat stores, and restores metabolic flexibility.

Let’s Keep This Party Going!

Above are the sharpest takedowns of CICO I’ve discovered on my travels down the Information Superhighway. But that’s obviously not ALL of them that exist.

What are your favorite anti-CICO arguments, studies, blog posts, or epic rants? Drop them in the comments!