There is a massive debate raging in the health world right now over a simple concept: calories. Do they rule the world or are they bystanders in the complexity of human physiology?

Conventional wisdom tells us that weight is controlled by the simple equation of calories in vs. calories out. The alternative health scene tells us that calories don’t really matter because things like food quality, digestion and hormones ultimate determine weight balance and health. There has been for quite some time a seesaw paradigm in the world of calories. Back and forth it goes as countless people, researchers, scientists, doctors and health “experts” debate over whether calories do or don’t matter. The law of thermodynamics gets put up against the neuro-regulation of appetite. Complicated equations and scientific theories get argued for and against. Articles, Facebook links and blog posts give birth to massively long comment threads as theories, explanations and rationale plays the seesaw game, tipping back and forth, often very heatedly, over this one seemingly unanswerable question: do calories matter?

For most of us, the scientific debate and argument might be fascinating at best and mind numbing at worst. But could we be fighting a winless battle? Meaning, are we trying too hard to solve a problem without an answer?

Rethinking Calories In vs. Calories Out

In my opinion, the battle over calories is a very complicated issue that we are spending too much energy (pun intended) to figure out. Do they matter or not? Yes to both. Ultimately, an organism regulates weight and expenditure through the medium of energy but due to the complexity of the body the issue isn’t as black and white as the calories you eat and what you burn. It shouldn’t be shocking that context matters in the calorie debate. For some people, in some situations, it will be a pretty straightforward equation and be closer to calories “do” matter. For other people, or those above people in different situations, calories are only part of the equation as the many variables of adaptive human physiology come into play. It also shouldn’t be shocking that the body has developed some impressive mechanisms to manage our simplistic efforts to outsmart it. So, although it may seem like we should be able to control our weight easily through managing calories in vs. calories out, it ends up being very difficult to manipulate due to the numerous intricate variables at hand.

Calories vs. Energy

Take the general concept at hand: Food we eat vs. energy we burn = bodyweight regulation. In the grand scheme it’s basically how it works but when you look at the details there’s much more to it than just adding up food labels and estimating how many calories you burn on the elliptical trainer or treadmill. To state it a bit more accurately, we should phrase thingd a bit differently: energy we take in vs. energy we expend = body energy regulation. Although seemingly very similar, it has a few distinct and crucial differences and allows us to begin to see how the body so dynamically manages and allocates energy. It also allows us to approach calories from this angle: calories matter but only in the context of how the body is functioning.

As usual, when it comes to the body there are no definite answers, it’s not black and white and there are always more than a few things to think about…

Food As Energy

Calories estimate the heat energy released when a substance (food) is burned, not how much useable energy it has when broken down by the body. The body doesn’t run on calories, it runs on ATP and chemical reactions. Calories are simply a proxy for a food’s potential to be turned into and used as energy in the body. Therefore energy potential relative to calorie value is often grossly inaccurate. Calorie values of food are also not a very accurate measure of food energy and are a rough estimate at best. Food labels and calculations therefore end up giving us an often inaccurate, inconsistent and highly variable account of the energy in any given food.

Not every calorie eaten ends up being absorbed. Estimating how much energy gets into your body is virtually impossible. Relative caloric value (RCV), (also known as digestive efficiency) the value of how much potential energy (and nutrients) of a food actually getting into the body to be used, is the real calorie or energy value of a food. The inherent problem: every body in every situation is different, which makes figuring out RCV literally impossible. Some people digest and absorb nearly every calorie they eat, others don’t digest and absorb well at all. This means an apple might have a RCV of 100 for someone and only 50 for someone else. Additionally, the current status of the body (stress, hormones, energy surplus/deficit, vitamin status, other foods eaten with it) all can affect, both positively and negatively, the real energy value of a food at any given moment for any given person.

Every calorie (fat, carb, protein) may be equal when burned in a chemistry lab but calories aren’t equal when they enter the body. Carbohydrates are counted as 4 calories per gram (although different forms of carbohydrate have different calorie values, 4 is an average), so if you eat, digest and assimilate every single bit you get (theoretically) 4 calories of energy per gram. Protein is also roughly 4 calories per gram but is not an “energy” macronutrient. So if you digest and assimilate every single amino acid, much of that goes toward structure and very little gets used as energy, so protein “calories” may be not be a measure of energy at all. Fat is roughly 9 calories per gram (also just an average across types of fat) and can be used for several purposes. Digest every single milligram of fat and you provide your body with a substrate it might use as energy or might use for structure. How do we know how much the body uses for what purpose? We don’t. At best we are educated guessing.

We expend energy just digesting food, particularly fiber and protein. It might take 1 calorie of energy to digest a gram of protein so instead of 4 calories of energy that gram of protein only has a net of 3 to your body. Same for fiber, which takes a lot of energy to digest depending on type and how much it’s been heated or chewed. The digestive cost of fiber could be anywhere from half to more energy than it could provide. Fiber also can be digested in the large intestine by bacteria which create short chain fatty acids which we absorb back into the system. So one gram of fiber, a carbohydrate which would be considered 4 calories of energy, would take a calorie or two (or maybe 3-5) to digest but then may be transformed into fat in the colon and absorbed at 3-9 calories. As you can see, the net energy of food is very tough to measure.

The bacterial environment in the digestive tract determines much of our energy assimilation and regulation. Depending upon the status and function of this micro biome, energy eaten may be over or under utilized by the bacteria, leaving an unknown amount left for us to even have access to. This bacterial realm and coexistence is so unknown right now that it’s best to simply concede that it plays a role beyond what we can even figure out at the moment so we need to keep that in mind when thinking about how the energy and calorie dynamic plays out.

Energy Expenditure

Your body adjusts it’s energy use every minute of every day based off the environmental information it senses/receives and what situations/adaptations it has stored in memory. Today your internal workings are different than yesterday and tomorrow and potentionally very different from a week, month or 10 years ago.

As an example, if you spent an hour on the treadmill today you may have (according to the machine) burned 400 calories. This is a rough estimate across all people completing that work but let’s just say it is perfectly accurate. You expended 400 units of energy. An important point to remember is that you would have expended energy if you sat next to the treadmill and watched it run for an hour. Probably about 100-150 calories. So spending an hour on a treadmill only increased your caloric burn by 250 calories over doing nothing. You didn’t burn an extra 400.

There’s also afterburn to consider. Depending upon the intensity and the muscle micro-damage of the exercise, extra energy will be needed to recover from and repair tissue which adds another variable to the equation. You could burn 400 calories with very little to no extra afterburn or you could get several hundred extra calories of energy demand afterward. This can be estimated (more strength and power oriented activities will generate more afterburn) but once again it’s a guess at best.

The next day will be different. If you complete the exact same activity you’re likely to burn a few less calories than the previous day. In fact, the more you do that activity the better your body gets at expending less energy to get it done. It becomes very efficient. Your body may or may not be in the same metabolic state as the previous day. If you’re at an energy deficit (particularly if it’s been ongoing/chronic) your body becomes more and more efficient and uses less energy each and every day, particularly when exercising. If you’re stressed you will burn different amounts of energy. If you’re under slept the body will burn, ration and store energy differently. Each person is different and the day to day changes will be different. This means it can be very difficult (nearly impossible) to estimate how many calories you burn in a given day.

Me & An Omelette

As a good example of how context matters in the calorie/energy story we can use my breakfast from a few days ago…

An hour or so after working out I had a decent size breakfast consisting of a bacon, turkey and tomato omelette, roasted potatoes and a slice of sourdough bread with butter. A decent size breakfast that was probably 600-700 calories. However, as you might imagine, my net energy intake may not be as simple as just logging 650 calories into my journal. After an hour workout, in which I expended a bunch of energy (would estimate ~300 extra calories), most of which was drawn from stored fat and glycogen, and also broke down a decent amount of muscle fibers, my body was a sponge for energy and nutrients. This means that much of the fat and carbohydrate will likely go straight into replenishing what I just expended and aren’t really useable energy. Same with the protein as much of that will shuttle to muscular repair. Much of what I ate literally disappeared and can’t be considered calories for the calories in equation.

This is operating under the assumption that I am digesting and assimilating all the energy of that meal which isn’t likely because it will be a while before my parasympathetic nervous system kicks in enough to let me get into primary digestion state. It isn’t a stretch to say that almost everything I end up getting from the meal might be shuttled into returning the body to homeostasis. Do those calories count the same as when I don’t work out? Not very likely. A body not depleted has very different priorities and demands. Additionally, I work on my feet, moving all day long (8-14 hours) so calories that digest into useable energy are going to get used pretty quickly. If I sat around after eating that meal the energy distribution and allocation would likely be dramatically different. When all is said and done, I can’t offer the slightest guess as to what my energy in vs. energy out would be that morning, much less the rest of the day. Might we be able to guess better in the future? Yes. But right now it’s still very challenging to accurately determine if calories are at all a decent proxy for energy.

The Frugal Finance of Energy

One of the best ways to understand how the body manages energy is to compare it to personal finance. Much like a household the body has a budget of income (energy in) and expense (energy released) that it tries to keep balanced and managed in a comfortable range.

Salary is what you eat (calories) but income (digested energy) is what you actually get to put into the bank. Just like taxes cut your paycheck a bit, your body doesn’t get every last bit of energy so income (assimilated, available energy) matters most. You have a checking account (working energy on a daily basis, most from digested food) and savings account (stored energy, fat and glycogen). As you eat, your income/money goes into your checking account and you use that during the day for your daily expenses. Most days things are pretty simple, we work pretty smoothly and spend what we make. If you make a bit more money on a given day (more energy digested) your body either spends that money (increases metabolism), saves it (stored as glycogen and/or fat) or a little bit of both. Your personal history and body status (stress, hormones, etc.) often determines how your body deals with the extra energy. If you make a little less on a given day you’ll tap into your savings a bit to pay your bills. But just like in the real world, if you draw upon your savings you will be looking to put some back come next paycheck. If you don’t make more money you’re likely to cut back on expenses (e.g. dining out) and use that extra money to replenish the savings you used. The body does the exact same thing.

Just like a smartly managed family budget, the body has a comfort zone with income, expenses and savings. It has a certain base level of savings (bodyfat) and tries to keep it substantial to be able to withstand a major income disaster (famine). Based off past earnings and income, the body sets a budget for all household members (muscles, brain, organs, etc.) and settles in to a way of life. The more you make the more you spend. The less you make the less you spend. Bills come up now and then, both expected and unexpected, and the body adjusts accordingly. As an example, exercise is a big expense for the the body and if you do it regularly the body will budget its income and expenses to keep its budget balanced. Spend a bunch of energy on a 5 mile run (which is a non essential expense) and you might draw out of savings (fat) but you’re more likely to cut back on something else in the budget that will get cut down to balance out.

When we look at trying to lose weight by the calories in vs. calories out philosophy, you really see how the financial model makes sense. The common method for weight loss is eat less and exercise more. Burn 3500 more calories than you eat and you lose a pound of fat. Seems simple enough until we look at it through the lens of a smart money manager: the body. What this philosophy is basically saying is spend $3500 more than you earn and you’ll drain your savings account of $3500. That may be fine if your body has plenty in its savings account and doesn’t have any worries about financial security. But what if it doesn’t have extra or isn’t comfortable with how much extra it has and needs? It’s going to make some adjustments to its budget. Not many families keep spending $3500 over what they make, week after week, month after month, whittling their savings down to nothing. In fact, pretty quickly changes are made. We start eating less and the body spends less. We add extra spending to the mix (exercise) and the body accountant gets even stingier. It has arrived at a nice comfortable bodyfat level (savings account balance) and doesn’t want to part with it unless necessary and justified.

Too much under budget (dieting) and someone won’t stop spending, particularly on non essential things (exercise)? Time to get clever to balance the budget. The body starts the equivalent of turning off lights, lowering the thermostat, bargain shopping and playing some tax manipulation. If you’re going to spend frivolous energy and cut back the income it’s going to make changes too. An financial/energy crisis leads the body to lower its metabolic rate both chronically and acutely. Every cell starts becoming a little more efficient and burning less energy and without you even knowing it, the body has closed the financial gap. Then it starts getting really good at finding tax exemptions to increase it’s income by increasing digestive efficiency and extracting more useable energy out of any calories eaten.

If you keep up the irresponsible spending without adequate income the body goes even further and pulls the equivalent of cutting of utilities. Cable, Internet, home security system, cleaners and gardeners all get fired or pared back. In the body this means hormone production, immune system, tissue repair and regeneration all get down regulated. The longer we force an energy deficit the more our body reacts by doing its best to manage that budget. Very rarely is the body willing to give up its savings account readily and consistently, much less while continuing a spending spree of energetic, vibrant metabolism. It has certain savings balance that it feels comfortable spending until it hits. This is why it’s often so difficult to lose weight simply by eating less and moving more and why we hit plateaus and gain weight back. You are cutting income and increasing expenses that aren’t necessary for survival. No accountant or CFO worth his/her paycheck would allow their company or family to operate this way. The body is no different and is considerably more advanced in its methods and micromanages its balance sheet every minute of every day in an attempt to always stay in budget or prepare for financial challenges that may lie ahead.

Caloric Quality

No conversation about calories can be complete without discussing the “quality” of those calories and how they impact the body metabolically and hormonally. This discussion can get massively intricate and complex but since this calorie discussion is already pretty long a summary of the salient points is probably more appropriate.

– Calories that come from whole, naturally occurring foods help the body regulate the energy budget well.
– Calories from isolated substances or food products are usually more difficult to manage and usually negatively affect the body’s ability to budget energy.
– Artificial sweeteners and flavors can hinder, mask or confuse energy intake and/or expenditure, leaving your body often confused as to how much energy you’ve actually ingested.
– The more nutrients (vitamins, minerals, etc.) that come with a calorie the more appropriately your body uses and manages the energy.
– Real food calories are like cash, while processed food calories are like IOUs or promissory notes.

Wrapping Up The Calorie Seesaw

As I have tried to establish, it’s extremely difficult to fully understand and predict energy uptake regulation and expenditure, making the calorie debate almost pointless, particularly the more adamantly one argues either extreme.
Due to this complex dynamic, the best approach is likely to acknowledge a few things:
1. Energy regulation is extremely dynamic and highly variable, both between and within individuals.
2. Calories do matter only when they become part of the energy intake and output of the organism, which ultimately determines weight, activity and health.
3. It is not quite as simple as reading food labels and then estimating caloric expenditure.
4. Energy regulation is moment to moment, day to day, week to week, month to month and is managed by our body’s financial energy budgeter, which has other higher level priorities than we are usually aware of.
5. The higher quality calories will be managed more straight forward while lower quality calories are harder to predict the outcome of. Good food helps your body manage energy well. Bad food impairs your body’s ability to manage energy.

Ultimately one of the greatest determinants of how much calories matter is how healthy the organism is. Healthy people have an easier time managing energy, and calories ultimately matter less. So when looking at calories they matter only in the context of the person eating them. For some people they matter a lot and for others they matter less. What doesn’t change is that the better food you eat, the healthier you get and the less any of this calorie seesaw even matters.

The bottom line on calories: What matters is the energy you ultimately derive and the info/signals your body gets from the calories you eat. Eating whole, natural foods helps gives your body good energy and supports it in making good use of that energy. Eating processed food products gives you unpredictable and supra normal energy and hinders it’s ability to manage it.

Our bodies are more complicated and advanced then we can hope to imagine so our best bet is to take a step back, respect what it’s trying to do and become an apprentice. Watch it, learn from it and support it. In time hopefully we can reach a place where the calorie debate is fun to think about but has no bearing on how we live our lives.

Thanks for reading, have a great day!