Is the adage “calories in, calories out” true? The short answer is yes, but the full story is more nuanced.
From the moment food touches your tongue to the time it leaves your body, your digestive system and gut microbiome work to extract its nutrients. Enzymes in your mouth, stomach and small intestine break down food for absorption, while microbes in your large intestine digest the leftovers.
“Calories in, calories out” refers to the concept that weight change is determined by the balance between the calories you consume and calories you expend. This includes not only the number of calories you eat due to appetite and absorb via digestion, but also how well those absorbed calories are burned through metabolism.
Recent research indicates that a significant factor influencing people’s variable appetites, digestion and metabolism are biologically active leftover components of food, known as bioactives. These bioactives play a key role in regulating the body’s metabolic control centers: your brain’s appetite center, the hypothalamus; your gut’s digestive bioreactor, the microbiome; and your cells’ metabolic powerhouses, the mitochondria.
I’m a gastroenterologist who has spent the past 20 years studying the gut microbiome’s role in metabolic disease. I’ll share how dietary bioactives help to explain why some people can eat more but gain less, and I’ll offer some dietary tools to improve metabolism.
Ruminating on appetite and digestion
Research has shown that consuming whole foods still “packaged” in their original fibers and polyphenols – the cellular wrappers and colorful compounds in plants that confer many of their health benefits – leads to more calories lost through stool, when compared with processed foods that have been “predigested” by factories into simple carbs, refined fats and additives.
This is one way calorie-free factors influence the “calories in, calories out” equation, which can be beneficial in a society where calorie intake often exceeds needs. Eating more whole foods and less processed foods simply lets you eat more because more of those unprocessed calories go out the other end unused.
Fiber and polyphenols also help regulate your appetite and calorie intake through the brain. Your microbiome transforms these leftover bioactives into metabolites – molecular byproducts of digestion – that naturally decrease your appetite. These metabolites regulate the same gut hormones that first inspired the popular weight loss drugs Wegovy, Ozempic and Mounjaro, controlling appetite through your brain’s satiety center, the hypothalamus.
Processed foods lack these bioactives and are further formulated with salt, sugar, fat and additives to be hyperpalatable, causing you to crave them and eat more.
Mitochondrial maestros in the middle
A full accounting of calories also depends on how effectively your body burns them to power your movement, thoughts, immunity and other functions – a process largely orchestrated by your mitochondria.
Healthy people typically have high-capacity mitochondria that easily process calories to fuel cellular functions. People with metabolic diseases have mitochondria that don’t work as well, contributing to bigger appetites, less muscle and increased fat storage.
They also have less of a mitochondria-rich type of fat called brown fat. Rather than storing calories, this fat burns them to produce heat. Less brown fat may help explain why some people with obesity can have lower body temperatures than those who aren’t obese, and why there has been a decline in average body temperature in the U.S. since the industrial revolution.
Healthy mitochondria that burn more calories might also help explain why some people can eat more without gaining weight. But this raises the question: Why do some people have healthier mitochondria than others?
Your mitochondrial health is ultimately influenced by many factors, including those usually associated with overall well-being: regular exercise, adequate sleep, stress management and healthy eating.
Who turned off the metabo-lights
The latest nutrition research is revealing the roles that previously underappreciated dietary factors play in mitochondrial health. Beyond the essential macronutrients – fat, protein and carbohydrates – and micronutrients such as vitamins and minerals, other leftover factors in food, including fibers, polyphenols, bioactive fats and fermentation products, are also key for metabolism.
Unlike a Western diet, which often lacks these bioactives, traditional diets such as the Mediterranean and Okinawan diets are rich in foods – nuts, seeds, fruits, vegetables, whole grains and fermented foods – replete with these factors. Many bioactives pass undigested through the small intestine to the large intestine, where the microbiome converts them into activated metabolites. These metabolites are then absorbed, influencing the number of mitochondria in cells and how they function.
At the most fundamental level of cell biology, metabolites turn on and off molecular switches in your genes through a process called epigenetics that can affect both you and your offspring. When the metabolic “lights” are turned on, they enliven the mitochondria responsible for a faster metabolism, effectively increasing the calories you use.
Please mind the microbiome gap
A healthy microbiome produces a full range of beneficial metabolites that support calorie-burning brown fat, muscle endurance and metabolic health. But not everyone has a microbiome capable of converting bioactives into their active metabolites.
Long-term consumption of processed foods, low in bioactives and high in salt and additives, can impair the microbiome’s ability to produce the metabolites needed for optimal mitochondrial health. Overuse of antibiotics, high stress and lack of exercise can also adversely affect microbiome and mitochondrial health.
This creates a double nutrition gap: a lack of healthy diet and a deficiency in the microbes to convert its bioactives. As a result, well-studied nutritional approaches such as the Mediterranean diet might be less effective in some people with an impaired microbiome, potentially leading to gastrointestinal symptoms such as diarrhea and negatively affecting metabolic health.
In these cases, nutrition research is exploring the potential health benefits of various low-carb diets that may bypass the need for a healthy microbiome. While the higher protein in these diets can reduce the microbiome’s production of beneficial metabolites, the lower carbs stimulate the body’s production of ketones. One ketone, beta-hydroxybutyrate, may function similarly to the microbiome metabolite butyrate in regulating mitochondria.
Emerging microbiome-targeting approaches might also prove helpful for improving your metabolic health: butyrate and other postbiotics to provide preformed microbiome metabolites, personalized nutrition to tailor your diet to your microbiome, intermittent fasting to help repair your microbiome, and the future possibility of live bacterial therapies to restore microbiome health.
Tools to transform fat into fuel
For most people, restoring the microbiome through traditional diets such as the Mediterranean diet remains biologically achievable, but it is not always practical due to challenges such as time, cost and taste preferences. In the end, maintaining metabolic health comes back to the deceptively simple healthy lifestyle pillars of exercise, sleep, stress management and nutritious diet.
Some simple tips and tools can nonetheless help make nutritious diet choices easier. Mnemonics such as the 4 F’s of food – fibers, polyphenols, unsaturated fats and ferments – can help you focus on foods that best support your microbiome and mitochondria with “leftovers.” Bioactive-powered calculators and apps can also aid in selecting foods to control your appetite, digestion and metabolism to rebalance your calorie “ins and outs.”
Christopher Damman is Associate Professor of Gastroenterology, School of Medicine, University of Washington.
The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.
© The Conversation
57 Comments
Mr Kipling
Fat people always looking for excuses for their excessive chubbyness. Its the sugar in drinks, its processed foods, its my metabolism.... NO, its you eating more than you need. Take responsibility.
Gene Hennigh
People who are not fat don't know much about. They just think they do. Telling someone, "Oh, don't be fat. Just don't eat so much", is like telling a person with severe depression, "Oh, just stop being depressed. Get over it". Actually knowing about a fat person and knowing one is the difference between idiotic diagnoses and genuine help.
Big
Calories in, calories out is BS that allows big food and big pharma (and doctors) to blame the individual for their situation, and continue to sell ultra processed garbage as though it's equivalent to non-processed food. Easy way to think about this: if calories in, calories out is reality that would mean 100 "calories" of lettuce and 100 "calories" of chocolate are equivalent. Calories are calculated by blowing up a sample of food and measuring the heat differential. That's not how your body works, your food doesn't explode upon ingestion.
Strangerland
The "it's simple" crowd never seem to be able to explain why everyone isn't doing it if it's so simple.
Big
Mr KiplingToday 10:06 am JST
Fat people always looking for excuses for their excessive chubbyness. Its the sugar in drinks, its processed foods, its my metabolism.... NO, its you eating more than you need. Take responsibility.
Not quite. When people are not educated about what nutrition actually is, and actively misdirected by doctors, pharma, food industry, and marketing; it's no wonder people continue making the same choices. Additionally, you can't fight against your hormones and once your hormones become messed up because of a lifetime of ultra-processed "food" consumption it's hard to break the cycle. Your comment strikes me as if you are the kind of person who would give advice like "just eat less and move more".
Moonraker
You are gonna die anyway. If you wanna get through it all eating and being turned on by food, it's fine. You are encouraged to anyway. Eating has been completely fetishised. Everyone gets to have an opinion about something that doesn't matter, be pretentious and even define themselves by what they eat. And as an "art" that has no oppositional qualities to it anyway food and cuisine is happily promoted by the exploitative system. Not only that but, like any good product should be, food is consumed almost at the point of buying so there is no lengthy appreciation before the desire for the next food hit kicks in. It's almost the perfect consumerist activity. Then we wonder why people are getting fat.
ian
That's basically it.
If you consume more calories than you use then the rest is stored as fat
If you want to get less fat you have to consume less calories, do more exercise or both.
You dont even have to understand or change what you eat, just eat less. Or move more. Or both.
ian
Difficult to suppress one's appetite so people turn to appetite suppressing drugs.
Or if you don't want to eat less then change the diet or part of it to something with less calories. Like carbs to fibers fats or proteins.
Whatever you do consult a health professional first.
Big
And to follow up on this. By your logic if I consume 2000 calories a day of standard Japanese fare (fish, rice, soup, veggies, etc.) and I want to lose weight I could be successful by changing my diet to eat only 1000 calories of Snickers bars every day instead.
And before you jump in and say "well obviously Snickers bars and junk food are different", you need to explain how one calorie is different to another.
ian
It's almost certain that you will lose weight that way.
Hawk
Big,
What foods should or shouldn't people be eating?
wallace
For five years during my post-cancer period, I have kept to a healthy diet and plenty of exercise. I put on an extra 15 kg from the cancer and have since lost about 10 kg. Another 5 kg to go. My daily calorie intake is about 1500. So calories in calories out is not the answer for everyone.
Raw Beer
”Calories in, calories out” is over simplistic and doesn't work. Not all calories are equal, unless you're a bomb calorimeter.
Eating carbs causes insulin release, which basically tells your body to not use your fat deposits, the opposite of what you want if weight loss is the goal.
If one instead gets most of their energy from fat, they become fat adapted allowing them to efficiently burn their fat, which is exactly what you want if weight loss is the goal.
Naah, I'll stick with BBBE - beef, butter, bacon, and eggs
Big
Real foods, ie. if it has a nutrition label there is little to no nutrition in it.
Hawk
Big,
I'm pretty sure that's what doctors advise, but thanks.
Big
So your answer indicates you think that a body (of any species) treats everything consumed the same way (ie. chocolate is treated the exact same way as broccoli)... in other words, you're not thinking, or you're a doctor.
ian
Hahahaha hilarious
Hawk
Big,
Sorry to bother you again. Links to medical associations that recommend eating chocolate over eating broccoli. Please and thank you.
Big
I think you're confusing me with Ian. I'm saying it's a ridiculous assumption, Ian thinks it's not.
Hawk
Big,
I'm not. I'm just wondering what advice you think doctors give to their patients. You seem to be very anti-doctor.
virusrex
As usual, there is always an "easy" solution that is not only not effective but instead make the problem worse, according to the best available evidence there is no merit on the fad diets that call for reduction of carbohydrates to unhealthy levels, and specially those that call for unhealthy levels of cholesterol to be ignored to push for more fats in the diet.
Specially bad is to to combine both unhealthy recommendations into a single terribly bad recommendation, which is why diets like keto and carnivore are considered unhealthy and not recommended by the medical community of the world. Unfortunately there will be always people that will try to mislead others into ignoring the medical advice by using the excuse of the impossible global conspiracy to explain why every institution say the same thing, just not something that anyone rational could ever believe.
Big
HawkToday 06:13 pm JST
Big,
I'm not. I'm just wondering what advice you think doctors give to their patients. You seem to be very anti-doctor.
I'm anti-doctor-giving-nutrition-advice because they know nothing about nutrition. This is why any nutrition "advice" you get from a doctor will be nebulous in nature, such as "calories in, calories out", "eat less move more", "it's all about balance". And none of this advice is correct or meaningful.
Hawk
Big,
Thanks again.
Well, I guess we just have to disagree. Personally, I have been lucky and have never struggled with my weight, but I'm pretty sure the standard medical advice is exactly the same as you just gave: eat real foods, avoid overly processed ones.
ian
Hahaha you plainly don't understand anything and now you're saying you know what I think hahaha .
No wonder youre saying what you're saying about doctors. Everything they say are probably completely opposite to what you "understand" so they're the ones who are dumb =)
Raw Beer
Yeah the "best available evidence" is responsible for the widespread obesity. There is no requirement for carbs, not even one gram. There is nothing unhealthy about cutting carbs, even cutting them completely. So yeah, cutting carbs is an easy solution, but few people try it because it goes against the advice given by the captured associations and the doctors who have little or no training in nutrition and just parrot what those associations recommend.
ian
Does this mean the basic or common diet of the Japanese is wrong and unhealthy?
wallace
Japanese have one of the longest life spans, and low obesity rates. They eat carbs too.
falseflagsteve
Most things I’ve are not easy especially breaking old habits or starting a new regime. Fad diets shouldn’t be encouraged for those that need to lose weight and/or get fitter. A lifestyle choice needs to be made, can do slowly and take your time but do t expect immediate noticeable results.
Walking more, maybe taking up a hobby involving sports, even buying dumbells van help. That with a change of diet, cut back on the packet meals and takeaways, cook at home. It’s fun to learn even if you aren’t used to and learn to shop wisely. There are markets about and small grocers that have bargains not found on the supers.
Derek Grebe
Short answer: yes.
Don’t snack, and don’t eat after 8pm.
I lost 26 kg that way over the last 2 years.
It’s simple self control,
Hawk
Raw Beer,
A couple of questions. Firstly, if people can't stick to somewhat restrictive diets, such as avoiding highly processed foods, how will they stick to very/extremely restrictive ones such as avoiding most or all carbs, or anything that isn't an animal product?
Secondly, low-carb diets have been around since the 1800s. If they are the one-size-fits-all solution, why didn't we avoid the obesity epidemic altogether? And don't say captured institutions, because the misunderstanding of processed carbs and all types of fat was in the 1980s, long after low-carb diets became a thing.
Lastly, do you recommend cutting all carbs for athletes? As I understand it, performing on energy from fat, not carbs, is like putting diesel in an F1 car. It might get you around the track, but you'll do it a lot better on high-octane.
falseflagsteve
Wallace
Thing is with carbs it’s where you get them from. If it’s rice and veg usually like Japanese do it’s ok as long as you’re getting your protein if you’re doing physical work. These days mostly in the West the carbs come from sugar in the form of fizzy drinks, sweets and cakes also many packet meals which have tons of hidden salt and sugars to enhance flavours.
Hawk
Derek Grebe,
Just like the first line of the article. Which then goes on to explain why it's not so simple.
Abe234
You're right but also society, politicians, factories, and food/corporate pyschologists have a part to play in this. Not to mention a few medical conditions. Low thyroid function slows downs the whole body system, so a person who is "UNDIAGNOSED" will gain wait even though they are not eating much and might be eating healthily. But schools, have a part to play too. Too much focus on certain subjects and the easiest lesson to cut first is P.E. Parents being forced to work can't find the time,(as theyre tired) to shop and cook healthy meals.So to save time, go to the freezer section and buy something made in a factory, and slam it in the oven. Snacks are now soooo cheap they have replaced fruit. Governments could reduce the tax and healthy food, and increase the tax (to counter balance it) on junk food. Schools could have ONLY HEALTHY FOOD. and NO snacks or junk. Sadly! Some areas of lost heavy industries so, some places have not jobs, except to work in JUNK food, pub industry. But yes. It ultimately comes down to the individual, but its like dealing with a drug dealer at the supermarket. Buy two get one free. Waiting at the checkout, sweets are staring at you for 10 minutes. Not fruit!. And supermarkets want that sudden impulse buy and kid pester power to get that extra dollar. Retail pyshology is now big business.VIsual pricing, cross selling,smell,signs,colors, and the SALE sign. These werent there 70.80 years ago.
jackandjill
I have eaten the same well-balanced diet with fresh foods for decades. I will continue to do so.
Raw Beer
Better than the standard American diet, but it can be better, especially if one wants to lose weight.
Well, we always hear that we need to reduce fat and meat intake. If they encouraged low carb diets, we wouldn't have this obesity epidemic.
Well, why else would these institutions, which are heavily funded by big food and big pharma, so consistently make the wrong recommendations?
virusrex
Doctors that deal with patients that require nutritional advice regularly take qualifications on the matter, becoming a nutritionist is not difficult for a doctor that already have the basis, which is typical for gastroenterologists, cardiologists, endocrinologist, etc. Most doctors that give advice know what they are talking about, or at least know enough to refer the patient to someone that does.
Obviously not, since most countries do not have this problem and the people that observe a healtht diet as recommended by the experts are not obese, this argument fails so completely it is difficult to think anybody would use it for any other purpose than to be obviously wrong. As mentioned, the Japanese diet is much more closer to what the experts recommend, according to you Japanese would then have more obesity problems than Americans (that very frequently don't follow the recommendations) do they?
Repeting a claim demonstrated as false with scientific evidence do not make it less mistaken, it only makes it more obvious you insist on something that has been demonstrated as wrong, cutting all carbohydrates is not healthy and instead it can be demonstrated as risky and unhealthy. The moment you choose to just repeat the claim instead of providing evidence of the contrary you are also accepting you don't have such evidence.
Still the same irrational and unbelievable excuse that creationists, flat earthers, homeopaths, etc. use when confronted with the absolute lack of support from any respected scientific institution. Either the whole scientific community of the world is wrong (and the mountains of evidence they have to prove their points false) or nameless people on the internet without any evidence are, it is easy to see which side is correct here.
virusrex
As demonstrated with the examples, they don't. People that follow the recommendations do not have the lifestyle problems, your premise is false, therefore you yourself demonstrate your conclusions are false as well.
Roger Gusain
I've been consuming my basic diet of McDonalds, Famichiki and beer for over 30 years now and I'm still alive. I will probably keel over soon, but I don't care. I just live one day at a time. A healthy lifestyle is not going to save us when we get zapped by a North Korean nuclear missile.
virusrex
So you have no argument whatsoever about the topic or comments, so you make baseless personal attacks instead? again trying to taunt the mods by openly disregarding the rules you promised to obey in order to comment?
virusrex
There is no abuse in claiming the scientific consensus contradicts a false claim.
You on the other hand make not even a tiny effort to address the topic and instead make childish personal attacks when someone contradicts something and you can't resist attacking the person since you can't do anything about the arguments.
Once again, you do this fully knowing you are commenting against the rules to taunt the mods.
Roger Gusain
I've been consuming my basic diet of McDonalds, Famichiki and beer for over 30 years now and I'm still alive. I will probably keel over soon, but I don't care. I just live one day at a time. A healthy lifestyle is not going to save us when we get zapped by a North Korean nuclear missile.
My main form of exercise is waddling to the conbini to load up on booze and junk food. Who needs gyms?
Hawk
More likely, they're not as simple or effective as claimed, and the problem is a lot more complicated.
It wouldn't matter, if your solution was as perfect as you say it is.
Hawk
A proven method of weight loss:
"Kevin Maginnis, 57, from Nashville says he ate half-portions of McDonald’s thrice daily and lost about 60lbs (26kg) in weight"
https://www.google.com/amp/s/amp.theguardian.com/us-news/2023/jun/03/mcdonalds-diet-weight-loss
(I'm joking - I do not recommend this. Consult a doctor first)
Wick's pencil
Riiight, it's a sign of great intelligence to believe everything that the authorities say.
But seriously, it takes a certain level of intelligence to realize that not all scientists are saying the same thing, and even more intelligence to understand which ones are correct.
virusrex
When the experts can prove it beyond any reasonable doubt? sure, it is the smart thing to do.
Not really, fringe and openly mistaken "scientists" contradict the consensus about everything, knowing this requires no intelligence, some will say infections are caused by miasma or "negative engergy" or that the planet is flat, but the consensus is still real even with these examples of professional ineptitude.
Knowing which ones are correct is a problem of having an open mind and being able to accept being wrong, if the ones that say the thing you like to hear are contradicting the consensus that means they are simply wrong, specially when they have blogs and youtube videos instead of scientific reports and evidence on their side.
Of course not everybody is able to accept their personal beliefs may be wrong, so these people will shop around until some hack with doubtful credentials support their personal opinion and will believe anything the grifters will push even if obviously false or nonsensical. In that case is more a case of being too self centered to use their intelligence, not a lack of it.
Zaphod
Mr Kipling
No, it is the sugar in drinks, it is the processed food. You can eat as much raw vegetables as you want; they won´t make you fat.
Zaphod
virusrex
Ah, but of course, "the experts". Not "all institutions in the world" this time?
Zaphod
Roger Gusain
"Keeling over" should not be a great concern, but what happens before that? The diabetes caused by all the sugar-loaden overprocessed junk is no fun. Think of a host of nasty symptoms, including amputation of limbs.
Zaphod
Big
Plenty of explanations of this available. You might start out by watching the famous "Sugar, the bitter truth" lecture by Dr. Lustig, which gives you all the background info that you could wish for. But really, common sense already should tell you that a calorie from a soft drink is not the same as a calorie from cabbage.
virusrex
That point is still correct, you have not been able to bring any institution yet to refute it, the consensus is clear.
Wick's pencil
Except that the so called experts haven't proven anything. At most they have cherry picked data to show some indirect correlations.
The doubts are very reasonable.
virusrex
The moment they published results with well validated methods that clearly points to a single conclusion, and that you have zero arguments against those reports it means they proved their point so completely you are left without any actual response except for the invalid excuse of everybody in the world being in a conspiracy to contradict what you believe.
Doubting the whole scientific community based on deep ignorance about the topic is not reasonable, it is the opposite.
Wick's pencil
Simply stating something does not make it true.
virusrex
You have never showed how the scientific consensus is wrong, that is a fact, not just a statement. This means the consensus is valid and correct and your claims do not hold any value. It is as rational a position as the flat earthers that say science have not proved the planet is not flat.
Raw Beer
No, you are constantly referring to a consensus of capture (corporate-funded) institutions.
If we're talking about actual SCIENTIFIC consensus, you have never shown how my earlier comment was wrong:
Eating carbs causes insulin release, which basically tells your body to not use your fat deposits, the opposite of what you want if weight loss is the goal.
If one instead gets most of their energy from fat, they become fat adapted allowing them to efficiently burn their fat, which is exactly what you want if weight loss is the goal.
virusrex
False, the consensus is about the whole scientific community of the world, exemplified by the absolute lack of institutions that contradict that consensus.
You are the one that baseless qualify as "captured" anything and everything that don't support your personal preference, which again is just an excuse, the same that every antiscientific groups try to use when confronted with clear evidence the scientific consensus is clear and strong. Flat earthers, creationists, etc. all talk about the whole scientific community as "captured" and talk about impossible global conspiracies without ever offering any evidence to contradict the consensus (much less prove the imaginary conspiracy) It is still an excuse and a very bad one.
The moment you could not find any example where a medical institution supports your claim that zero carbohydrates is a desirable thing in a healthy diet, zero. That demonstrates more than anything else that the consensus is the opposite of what you wanted to believe. Zero institutions.
Raw Beer
That is classic appeal to authority.
The whole scientific community of the world and formal institutions are two separate things.
Again, appeal to authority. That is all you have.
Do you agree or disagree that eating carbs causes insulin release?
Do you agree or disagree that insulin promotes lipid synthesis/storage and inhibits the breakdown of lipids and FFA oxidation?
Considering these well established facts of human metabolism (AKA scientific consensus), how do you think continuing to stuff one's face with carbs will help to reduce obesity???
Why would institutions continue to recommend obese people to stuff their faces with carbs???