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Calories in vs. out? Or hormones? The debate is finally over. Here’s who won.


When it comes to body change, there’s no topic more polarizing than “calories in vs. calories out.” Some argue it’s the be-all and end-all of weight loss. Others say it’s oversimplified and misguided. In this article, we explore every angle of the debate from “eat less, move more,” to hormonal issues, to diets that offer a “metabolic advantage.” In doing so, we answer—once and for all—how important calories in vs. calories out really is.


“You’re either with me, or you’re against me.”


Everyone’s heard this one. But did you know the health and fitness industry has its own version of the saying? It goes: “You’re either with me, or you’re stupid.”


But this kind of binary mindset does fuel plenty of heated debates. Especially when it comes to one topic in particular: “calories in vs. calories out,” or CICO.


CICO is an easy way of saying:


  • When you take in more energy than you burn, you gain weight.
  • When you take in less energy than you burn, you lose weight.


This is a fundamental concept in body weight regulation, and about as close to scientific fact as we can get.


Then why is CICO the source of so much disagreement?


It’s all about the extremes.


At one end of the debate, there’s a group who believes CICO is straightforward. If you aren’t losing weight, the reason is simple: You’re either eating too many calories, or not moving enough, or both. Just eat less and move more.


At the other end is a group who believes CICO is broken (or even a complete myth). These critics say it doesn’t account for hormone imbalances, insulin resistance, polycystic ovary syndrome (PCOS), and other health problems that affect metabolism. They often claim certain diets and foods provide a “metabolic advantage,” helping you lose weight without worrying about CICO.


Neither viewpoint is completely wrong.


But neither is completely right, either.


This article will add some nuance to the debate.


We’ll start by clearing up some misconceptions about CICO. And then explore several real-world examples showing how far-right or far-left views can hold folks back.


Rethinking common misconceptions.


Much of the CICO debate—as with many other debates—stems from misconceptions, oversimplifications, and a failure (by both sides) to find a shared understanding of concepts.


CICO goes beyond food and exercise.


There’s an important distinction to be made between CICO and “eat less, move more.” But people, especially some CICO advocates, tend to conflate the two.


“Eat less, move more” only takes into account the calories you eat and the calories you burn through exercise and other daily movement. But CICO is really an informal way of expressing the Energy Balance Equation, which is far more involved.


The Energy Balance Equation—and therefore CICO—includes all the complex inner workings of the body, as well as the external factors that ultimately impact “calories in” and “calories out.”


Imperative to this, and often overlooked, is your brain. It’s constantly monitoring and controlling CICO. Think of it as mission control, sending and receiving messages that involve your gut, hormones, organs, muscles, bones, fat cells, external stimuli (and more), to help balance “energy in” and “energy out.”


It’s one hell of a complicated—and beautiful—system.


Yet the Energy Balance Equation itself looks really simple. Here it is:


[Energy in] – [Energy out] = Changes in body stores*


Body stores refers to all the tissues available for breakdown, such as fat, muscle, organ, and bone. I purposely haven’t used “change in body weight” here because I want to exclude water weight, which can change body weight independent of energy balance. In other words, water is a confusing, confounding variable that tricks people into thinking energy balance is broken when it’s not.


With this equation, “energy in” and “energy out” aren’t just calories from food and exercise. 


Calorie calculators and CICO aren’t the same.


Many people use calorie calculators to estimate their energy needs, and to  approximate how many calories they’ve eaten. But sometimes these tools don’t seem to work. As a result, these individuals start to question whether CICO is broken. (Or whether they’re broken).


The key words here are “estimate” and “approximate.”


That’s because calorie calculators aren’t necessarily accurate.


For starters, they provide an output based on averages, and can be off by as much as 20-30 percent in normal, young, healthy people. They may vary even more in older, clinical, or obese populations.


And that’s just on the “energy out” side.


The number of calories you eat—or your “energy in”—is also just an estimate.


For example, the FDA allows inaccuracies of up to 20% on label calorie counts, and research shows restaurant nutrition information can be off by 100-300 calories per food item.


What’s more, even if you were able to accurately weigh and measure every morsel you eat, you still wouldn’t have an exact “calories in” number. That’s because there are other confounding factors, such as:


  • We don’t absorb all of the calories we consume. And absorption rates vary across food types. (Example: We absorb more calories than estimated from fiber-rich foods, and less calories than estimated from nuts and seeds.)
  • We all absorb calories uniquely based on our individual gut bacteria.
  • Cooking, blending, or chopping food generally makes more calories available for absorption than may appear on a nutrition label.


Of course, this doesn’t mean CICO doesn’t work. It only means the tools we have to estimate “calories in” and “calories out” are limited.


To be crystal clear: Calorie calculators can still be very helpful for some people. But it’s important to be aware of their limitations. If you’re going to use one, do so as a rough starting point, not a definitive “answer.”


CICO might sound simple, but it’s not.


There’s no getting around it: If you aren’t losing weight, you either need to decrease “energy in” or increase “energy out.” But as you’ve already seen, that may involve far more than just pushing away your plate or spending more time at the gym.


For instance, it may require you to:


  • Get more high-quality sleep to better regulate hunger hormones, improve recovery, and increase metabolic output
  • Try stress resilience techniques like meditation, deep breathing, and spending time in nature
  • Increase your daily non-exercise movement by parking the car a few blocks away from your destination, taking the stairs, and/or standing while you work
  • Trade some high-intensity exercise for lower-intensity activities, in order to aid recovery and reduce systemic stress
  • Improve the quality of what you’re eating, as opposed to reducing the quantity. This can allow you to eat more food with fewer total calories
  • Tinker with the macronutrient makeup of what you eat. For example: eating more protein and fiber, or increasing carbs and lowering fats, or vice versa
  • Experiment with the frequency and timing of your meals and snacks, based on personal preferences and appetite cues
  • Consider temporarily tracking your food intake—via hand portions or weighing/measuring—to ensure you’re eating what you think you’re eating (as closely as reasonably possible)
  • Evaluate and correct nutritional deficiencies, for more energy during workouts (and in everyday life)
  • Consult with your physician or specialists if consistent lifestyle changes aren’t moving the needle


Sometimes the solutions are obvious; sometimes they aren’t. But with CICO, the answers are there, if you keep your mind open and examine every factor.


Imagine yourself a “calorie conductor” who oversees and fine-tunes many actions to create metabolic harmony. You’re looking for anything that could be out of sync.


This takes lots of practice.


Reference:  Precision Nutrition