Level 1: Calories in versus out? Or hormones? The debate is finally over. Here's who won.

When it comes to body changes, there is no more polarizing topic than "calories in vs. calories out". Some claim it is the be-all and end-all of weight loss. Others say it is too easy and wrong. In this article, we examine every aspect of the debate, from "eat less, move more" to hormonal problems and diets that offer a "metabolic benefit". We answer once and for all how important calorie input and calorie expenditure really are. And discuss what it means for you and your customers.
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"You are either with me or you are against me."
Everyone heard that. But did you know that the health and fitness industry has its own version of the saying? It says: "You are either with me or you are stupid."
I child of course!
But this kind of binary thinking drives a lot of heated debates. Especially when it comes to a specific topic: "Pure calories vs. Calories Out ”or CICO.
CICO is an easy way to say:
- If you absorb more energy than you burn, you gain weight.
- If you absorb less energy than you burn, you will lose weight.
This is a basic concept in body weight regulation and as close as possible to scientific facts.
Then why is CICO the source of so many disagreements?
It's all about extremes.
At the end of the debate there is a group that CICO believes is straightforward. If you don't lose weight, the reason is simple: you either eat too many calories, or don't exercise enough, or both. Just eat less and exercise more.
At the other end is a group that believes CICO is broken (or even a complete myth). These critics say that hormone disorders, insulin resistance, polycystic ovary syndrome (PCOS) and other health problems that affect metabolism are not taken into account. They often claim that certain diets and foods offer a “metabolic benefit” that helps you lose weight without worrying about CICO.
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Neither view is completely wrong.
But neither is quite right either.
Regardless of whether you are a health and fitness coach to assist clients with weight control or if you are trying to learn this yourself, it is problematic to take an extreme position on this issue. It prevents you from seeing the bigger picture.
This article will add a certain nuance to the debate.
I'm starting to clear up some misunderstandings about CICO. And then examine some real-world examples that show how far right or far left views can hold people back.
Rethink common misunderstandings.
Much of the CICO debate, like many other debates, is based on misconceptions, simplifications, and the failure (on both sides) to find a common understanding of the concepts. So let's start by putting everyone on the same page for a change.
CICO goes beyond eating and exercise.
There is an important difference between CICO and "eat less, move more". But people, especially some CICO supporters, tend to merge the two.
"Eat less, move more" only takes into account the calories you eat and the calories you burn through exercise and other daily movements. But CICO is really an informal way to express the energy balance equation, which is far more complicated.
The energy balance equation – and thus CICO – encompasses all complex internal functions of the body as well as the external factors that ultimately affect calorie intake and calorie expenditure.
Your brain is essential for this and is often overlooked. It constantly monitors and controls CICO. Think of it as mission control by sending and receiving messages that affect your gut, hormones, organs, muscles, bones, fat cells, external stimuli (and more) to balance "energy in" and "energy out" to find.
It's a hell of a complicated – and beautiful – system.
However, the energy balance equation itself looks very simple. Here it is:
- (Energy in) – (Energy out) = changes in body stores *
* Body stores refer to all tissues available for breakdown such as fat, muscles, organs and bones. I purposely did not use a "change in body weight" here because I want to exclude water weight, which can change body weight regardless of energy balance. In other words, water is a confusing, confusing variable that makes people think that the energy balance is broken when it isn't.
With this equation, "energy in" and "energy out" are not just calories from food and exercise. As you can see in the figure below, all types of factors affect these two variables.
If you look at CICO through this lens – by zooming it out from a wider perspective – you can see that if you reduce it to "eat less, move more", it will be a significant simplification.
Calorie calculator and CICO are not the same thing.
Many people use calorie calculators to estimate their energy needs and to estimate how many calories they have eaten. But sometimes these tools don't seem to work. As a result, these people start asking if CICO is broken. (Or if they are broken)
The key words here are "estimate" and "approximately".
This is because calorie calculators are not necessarily accurate.
To begin with, they provide performance based on averages and can vary by up to 20 to 30 percent in normal, young, healthy people. They can vary even more in older, clinical, or obese populations.
And that's only on the energy side.
The number of calories you eat – or your "energy in" – is also only an estimate.
For example, the FDA allows inaccuracies of up to 20% when calorie counting on the label, and research shows that the nutritional information in the restaurant can vary by 100 to 300 calories per food.
Even if you were able to accurately weigh and measure every bite you eat, you still wouldn't have an accurate number of calories. This is because there are other confounding factors, such as:
- We don't take in all the calories we consume. The absorption rates vary depending on the type of food. (Example: We absorb more calories than estimated from high-fiber foods and fewer calories than estimated from nuts and seeds.)
- We all absorb calories based on our individual gut bacteria.
- Cooking, mixing, or chopping food generally leaves more calories available for absorption than is indicated on a nutrition label.
Of course, this does not mean that CICO does not work. This just means that the tools we need to estimate “calories in” and “calories out” are limited.
To be very clear: calorie calculators can still be very helpful for some people. However, it is important to be aware of your limits. If you want to use one, do so as a rough starting point and not as a final "answer".
CICO does not require a calorie count.
At Precision Nutrition, we sometimes use calorie counting to help customers improve their food intake. In other cases, we use hand portions. And sometimes we use more intuitive approaches.
For example, suppose a customer wants to lose weight but doesn't see the results they want. If they count calories or use hand portions, we can use these numbers as a reference to further reduce the amount of food they eat. We could also encourage them to use other techniques instead. For example, eat slowly or until they are 80 percent full.
In any case – whether we are talking about numbers or not – we manipulate "energy in". Sometimes directly; sometimes indirectly. So don't make a mistake: Even if we don't "count calories", CICO continues to apply.
CICO may sound simple, but it is not.
There is no getting around it: If you (or a customer) does not lose weight, you either have to decrease the energy intake or increase the energy intake. But as you've seen, this can mean a lot more than just pushing the plate away or spending more time in the gym.
For example, you can request:
- Get more quality sleep to better regulate hunger hormones, improve regeneration and increase metabolism
- Try stress resilience techniques like meditation, deep breathingand expenses Time in nature
- Increase your daily movement without movement Park the car a few blocks away from your goal take the stairsand or standing while you work
- Exchange a high-intensity exercise for one Lower intensity activitiesto support recovery and reduce systemic stress
- Improve that quality of what you eatas opposed to reducing the amount. This can allow you to eat more foods with fewer total calories
- Make whatever you eat with the macronutrient makeup. For example: food more protein and fiber, or Increase carbohydrates and lower fats, or and vice versa
- Experiment with that Frequency and timing of your meals and snacks based on personal preferences and appetite stimuli
- Consider Temporarily track your food intake– via hand portions or weighing / measuring – to ensure that you eat what you think you eat (as accurately as possible)
- Rate and correct Malnutrition, for more energy during training (and in everyday life)
- Ask your doctor or specialists when consistent lifestyle changes do not move the needle
Sometimes the solutions are obvious; sometimes they are not. But with CICO, the answers are there if you keep your mind open and examine every factor.
Imagine a “calorie guide” who monitors and refines many actions to create metabolic harmony. You're looking for something that may be out of sync.
This takes a lot of practice.
To help, here are 5 common energy balance dilemmas. In any case, it may be tempting to assume that CICO does not apply. However, if you take a closer look, you will find that the principles of CICO are always there.
5 common energy balance dilemmas.
Dilemma # 1: "I've always eaten the same way, but suddenly I gained weight."
Can you guess what happened?
Most likely "energy in" or "energy out" did change, but in a way that felt out of control or unnoticed.
The culprit could be:
- Slight increase in food intake due to mood swings, hunger or stress
- An increase in the amount of energy absorbed – caused by new drugs, an unknown illness, or a history of chronic diets
- Physiological changes that resulted in fewer calories being burned during exercise and at rest
- The onset of chronic pain leads to a dramatic decrease in thermogenesis of activity outside of training (NEAT).
- Significant changes in sleep quality and / or quantity that affect metabolism and / or food consumed
In all these cases, CICO is still valid. The energy balance has shifted subtly due to changes in lifestyle and health, making it difficult to recognize.
Dilemma # 2: "My hormones destroy my metabolism and I can't stop gaining weight. Help!"
Hormones seem to be a logical scapegoat for weight changes.
And although they're probably not to blame as often as people think, hormones are closely related to energy balance.
Nevertheless, they do not work independently of the energy balance.
In other words, people don't gain weight because of "hormones".
They gain weight because their hormones affect their energy balance.
This often happens during menopause or when the thyroid hormone level drops.
Take, for example, triiodothyronine (T3) and thyroxine (T4), two thyroid hormones that are incredibly important for metabolic function. If the level of these hormones decreases, weight gain may result. However, this doesn't negate CICO: your hormones simply affect energy intake.
This may seem a bit like splitting hair, but it's an important link whether it's menopause, thyroid problems, insulin resistance, or other hormonal issues.
If you understand that CICO is the true determinant of weight loss, you have a lot more tools to get the result you want.
Suppose you work with the wrong premise. Hormones are the only thing that matters. This can lead to increasingly unhelpful decisions, e.g. For example, a large sum of money for unnecessary food supplements or for adhering to an overly restrictive diet that will fail in the long run.
Instead, you know that the results depend on the fact that "energy in" or "energy out" has changed. This change can now be due to hormones. In this case, you need to adjust your eating, exercise and / or lifestyle to take this into account. (This may include taking medications that your doctor has prescribed for you.)
Research suggests that people with mild (10-15% of the population) to moderately severe hypothyroidism (2-3%) may experience a metabolic slowdown of 140 to 360 calories a day.
This can be enough to make you gain weight or make it difficult to lose weight. (One caveat: mild hypothyroidism can be so mild that many people don't notice a significant shift in metabolic activity, making it not a problem.)
In addition, hormonal changes that disrupt the energy balance can occur in women with polycystic ovarian syndrome (PCOS) (approx. 5-10%) and in menopause.
It is therefore important to understand your health (or that of your customer) as it provides valuable information about the particular challenges and how to proceed.
Dilemma # 3: "I only eat 1,000 calories a day and I still don't lose weight!"
So what is there?
The conclusion most people jump to: their metabolism is disrupted. They are broken. And CICO is broken.
But here's the deal: Metabolic damage is not really a thing. Even if it seems so.
Now, their energy balance challenge could be related to a hormonal problem, as discussed above. However, if someone eats 1,000 calories a day but does not lose weight, it is usually due to one of two reasons.
(No matter how simple they sound, we've seen that again and again in our coaching program with over 100,000 customers.)
Reason # 1: People often underestimate their calorie intake.
It is easy to calculate how much you eat, as this is usually unintentional. The most typical way people do it:
- You underestimate parts. (Without measuring, for example, "a tablespoon of peanut butter", there could actually be two, adding 90 calories each time.)
- They do not capture bites, licks and tastes of high-calorie foods. (For example, your child's leftover mac and cheese could easily add 100 calories.)
- You are not recording everything at the moment and forget to log it later
- They "forget" to count foods they wished they hadn't eaten
Don't you think this can be a big problem?
A groundbreaking study and repeated follow-up studies found that people often underestimate how much they eat during the day, sometimes by more than 1,000 calories.
I am not addressing this research to indicate that it is impossible to be realistic about portion sizes. However, if you (or your customers) don't see results on a low-calorie diet, keep in mind that underestimating can be the problem.
Reason # 2: People eat too much on weekends.
Working weeks can be stressful, and when Friday night rolls around, people put their watch down and let go.
(You probably can't refer to it, but just try, okay?)
Here's how: Let's say a person eats 1,500 calories a day on weekdays, which would result in an approximate 500 calorie deficit.
But on weekends, they deviate little from their schedule.
- Drinks with friends and a few slices of pizza on Friday
- An extra large lunch after training on Saturday
- Sunday brunch ("Hey, it's breakfast and lunch so I can eat twice!)
The last record: an additional 4,000 calories that are consumed between Friday evening and Sunday afternoon. They have effectively made up for their deficit and increased their average daily calories to 2,071.
The result: If you (or your customer) have drastically reduced your calories but don't see the expected results, look for the little slips. It's like being a metabolic detective who – literally – follows the bread crumbs.
By the way, if downtime is a problem for you (or a customer), we have just the thing: 5 surprising strategies to avoid overeating on the weekend.
Dilemma # 4: "I eat as much as I want and I'm still losing weight, so this diet is better than everyone else!"
This could be the main reason why some people reject CICO.
Suppose someone switches from a diet that is primarily processed foods to a diet that is primarily whole plant foods. You might find that you can eat as much as you want, but the pounds are still melting away.
People often believe that this is due to the "power of plants".
Yes, plants are great, but this doesn't disprove the energy balance.
Because plant foods have a very low energy density, you can eat a lot of them and still have a calorie deficit. Especially if your previous intake was filled with a lot of processed, hyper-tasty "stimulants".
It feels as if you're eating a lot more than ever – and in fact you could be.
In addition, the volume, fiber, and water content of the plants may make you feel more saturated.
It's all great. Really. But CICO doesn't negate it.
Or take the ketogenic diet, for example.
Here someone may have a similar experience of "eating as much as they want" and still losing weight, but instead of eating plant-based foods, they eat meat, cheese, and eggs. These foods are not low in calories and do not contain much fiber.
As a result, many low-carb advocates claim that keto offers a “metabolic advantage” over other diets.
The most likely thing to happen:
- A higher protein intake increases the feeling of satiety and reduces the appetite
- The limited selection of foods has cut out hundreds of highly processed calories that they might otherwise have eaten (pasta! Chips! Cookies!).
- Reduced food options can also lead to "sensory specific satiety". That means if you eat the same foods all the time, they may become less attractive, so you won't have to eat as much
- Liquid calories – soda, juice, even milk – are generally prohibited, so a larger proportion of the calories are consumed from solid foods that are more filling
- Higher ketone levels in the blood – which increase with reduced carbohydrates – seem to suppress appetite
For these reasons, people tend to eat fewer calories and feel less hungry.
Although it may seem magical, the keto diet leads to weight loss by regulating the "energy supply" in various ways.
You might ask: If herbal and keto diets work so well, why should anyone care if this is due to CICO or for any other reason?
Because depending on the person – food preferences, lifestyle, activity level, etc. – many diets, including plant and keto diets, are not sustainable in the long run. This is especially true for the more restrictive approaches.
And if you (or your customer) believe that there is only one "best diet", you may get frustrated if you can't stick to it. You can consider yourself a failure and decide that you lack the discipline to lose weight. You might even think you should stop trying.
None of this is true.
Your results are not diet-dependent. They are behavior dependent.
Maintaining a healthy body (including a healthy body weight) is about developing consistent, sustainable everyday habits that help you positively influence "energy in" and "energy out".
This can be accomplished while enjoying the foods you love by:
- Eat until you are 80% full
- Eat slowly and carefully
- Eat more minimally processed foods
- More sleep quality
- Take measures to reduce stress and build resilience
It's about looking at CICO from a distance of 30,000 feet and figuring out which approach it feels reasonable and attainable she.
Sure, that could include an herbal or keto diet, but absolutely not. And you know what?
You can get great results in either case.
Dilemma # 5: "I want to gain weight, but no matter how much I eat, I can't seem to."
The CICO conversation isn't always about weight loss.
Some people have difficulty gaining weight.
Especially younger athletes and people who are very, very active at work. (Think: jobs that involve manual labor.)
It also happens to those who try to lose weight after an illness.
If someone deliberately eats more food but cannot pack on the pounds, CICO appears to be invalid. (Surprise.)
They often feel like they are stuffing themselves – "I eat everything in sight!" – and it just doesn't work. But our trainers found the following:
People tend to remember extremes.
Someone could have had six meals a day and eaten as much as they wanted.
But the next day, they only ate two meals because they were so full. Maybe they were very busy too, so they didn't even think about it much.
The first day – the day they stuffed themselves – would probably stand out much more than the day they ate according to their hunger. It is only human nature.
It is easy to see how CICO is involved here. There is a lack of consistency with the "energy in" part of the equation.
One solution: Instead of filling yourself with 3,000 calories in one day and eating 1,500 the next, you should aim for calorie intake just above the middle to stay with, and increase it in small amounts over time if necessary.
People often increase activity when they increase calories.
When some people suddenly have more energy available – when they eat more – they are more likely to do things that increase their energy. As if you were taking the stairs, walking up and down on the phone and wriggling in their seats.
You could even push harder than normal during exercise.
This can be both subconscious and subtle.
And although it may sound strange, our trainers have identified this as a legitimate problem for "hard gainers".
Your fee: consider all your activities.
If you can't limit part of it, you may have to compensate for it by eating more. Foods rich in nutrients and calories such as nut butter, whole grains and oils can be helpful, especially if you have anorexia.
3 strategies to play the system.
Once you accept that CICO is both complex and inevitable, you may face a very common challenge.
Namely: "I can't eat less than I do now!"
This is one of the main reasons why people give up their efforts to lose weight or look for a miracle diet in vain.
But here are three simple strategies that you (or your customers) can use to create a calorie deficit, even if that seems impossible. It's about figuring out which one is best for you.
Maximize protein and fiber.
Consuming higher amounts of protein increases the feeling of satiety and helps you to feel more satisfied between meals. As you eat more fiber, satiety increases and you feel happier during meals.
These have been proven in both research and practice to help you feel happier overall while eating fewer calories, which results in easier fat loss.
This advice can sound banal, I know. In fact, one day when there are nutrition coach robots, "eating more protein and fiber" will likely be the first thing to program them.
But the truth is, most people who try to lose weight still don't focus on getting plenty of these two nutrients.
And you know what? It is not your fault.
When it comes to dieting, almost everyone has been told to withdraw. Take away the "bad" stuff and only eat the "good" stuff.
But there is another approach: just start adding.
If you make concerted efforts to increase your protein (especially lean protein) and fiber (especially vegetable) intake, you will be more satisfied.
You will also be less tempted by all the foods you should avoid. This helps to automatically “displace” ultra-processed foods.
Which leads to another big advantage: if you eat more whole foods and less processed foods, you are actually re-training your brain to covet these pampering, ultra-processed foods.
Then something cool happens: you eat fewer calories without trying actively – instead of deliberately limiting because you have to.
That makes weight loss easier.
Starting is easy: for protein, add a palm of relatively lean protein – chicken, fish, tempeh – to a meal. This goes beyond what you would otherwise have had. Or have a super shake as a meal or snack.
For fiber, add a serving of high-fiber food – especially vegetables, fruits, lentils, and beans – to your regular intake. This may mean that you have an apple for a snack, including a handful of roasted carrots for dinner, or a handful of spinach in your Super Shake.
Try this for two weeks, then add another palm of lean protein and another serving of high-fiber foods.
In addition to all the advantages we've discussed so far, there are also:
By coming to the table with an attitude of abundance rather than scarcity, you can avoid the anxious, frustrated feelings that are often associated with deprivation of the foods you love.
Instead of saying, "Ugh, I really don't think I can give up my nightly wine and chocolate habit," you could say, "Hey, look at all this delicious, healthy food that I can give my body!"
(By the way, you don't have to give up your wine and chocolate habit, at least not to make progress.)
Change your perspective.
Imagine you are on vacation. You slept and missed breakfast.
Of course you don't mind because you are relaxed and have a great time. And there is no need to panic: lunch will take place.
But since you've removed a meal, you end up eating a few hundred calories less than normal for the day, effectively leading to a deficit.
When you are in an environment where you feel calm and happy, you hardly notice it.
Suppose you wake up on a normal day and actively try to lose weight. (To prepare for the vacation!)
You might think, "I only get my 400 calorie breakfast and it is not enough food. That is the worst. I will be so hungry all day!"
So you're on your way to work stressed out and counting down the minutes to your next snack or meal. You may even feel disadvantaged and miserable.
Here's the thing: you had a calorie deficit on both days, but your subjective experience was completely different.
What if you could adjust your thinking to be more like the first than the second scenario?
Of course, I'm not suggesting that you skip breakfast every day (unless that's just your preference).
But when you manage to see less food as something you are doing – rather than something you have to – it can feel a lot less awful.
Add activity instead of subtracting calories.
Are you a person who doesn't want to eat less but would like to exercise more? In that case, you might be able to take advantage of what I called G-Flux.
G-Flux, also known as “energy flow”, is the total amount of energy that flows in and out of a system.
Suppose you want to create a 500 calorie deficit. It could look like this:
- Energy in: 2,000 calories
- Energy from: 2,500 calories
- Deficit: 500 calories
But it could also look like this:
- Energy in: 3,000 calories
- Energy from: 3,500 calories
- Deficit: 500 calories
In both scenarios you are 500 calorie deficit, but in the second you can eat much eat more.
This is a benefit of a larger G-Flux.
But there's another one: Research has shown that you can eat more calories and less fat by eating foods from quality sources and doing a variety of workouts – strength training, conditioning, and recovery work.
This is because the increased movement is not just there to increase your "energy". It also changes the distribution of nutrients, sending more calories towards muscle growth and fewer to your fat cells.
Plus, as you eat more, you have more options for getting the amounts of vitamins, minerals, and phytonutrients you need to feel good about yourself.
Victory. Victory. Victory.
This is a slightly more advanced method. And because metabolism and energy balance are dynamic in nature, the effectiveness of this method can vary from person to person.
Also, not everyone has the ability or desire to spend more time exercising. And that's okay.
However, by thinking flexibly and being willing to experiment with different ways of influencing CICO, you can find your personal strategy to improve the energy balance in your favor (or in favor of your customers).
If you are or want to be a trainer …
Learning how to coach clients, patients, friends, or family members through healthy eating and lifestyle changes – in ways that are tailored to their unique body, preferences, and lifestyle – is both an art and a science.
If you want to learn more about both, consider the Precision Nutrition Level 1 certification. The next group will start shortly.