Calories In vs. Calories Out: Why The Simple Equation Isn’t So Simple (UPDATED)
In honor of Men’s Health Month (June), let’s focus on a hot topic that is discussed on a regular basis in the health space. Many of us have the goal of losing fat or building muscle. Either way, calories run the show! In this article, we’ll dive into how calories are manipulated inside and outside of our bodies to direct us towards or away from our health goals!
Is a Calorie a Calorie?
In a chemical sense, yes. A calorie is a standard unit of energy.
According to the law of thermodynamics, if you expend more calories than you metabolize, you will expend the extra stored energy as fuel (commonly known as burning fat).
However, this process of “calories in vs. calories out” is extremely complex! Each of these two variables, and the precise balance between them, depend significantly on a range of factors. We’ll start with the first variable, “calories in”.
Calories In – Potential Factors
Has the food been refined or processed?
Processed food tends to take less energy to digest and metabolize (even when the calories on the label are equated). These foods are often “pre-digested” by removing parts of the less-tasty, but nutritious, aspects of the food. By breaking the food down during the manufacturing process, your digestive system doesn’t have to expend as much energy to break it down in your body.
How many of the calories come from protein or fiber?
Each macronutrient has different thermogenic effects. This is essentially just how many calories are expended throughout the digestive process. Protein and fiber both take a lot more energy to break down and digest than carbs and fat. For protein, ~30% of the calories consumed are expended during the digestive process. For fiber, it’s closer to ~20%. Sugars or starchy carbs (5-10%) and fats (0-3%) have much lower thermic effects.
On paper, 100 calories of white bread may appear to be equivalent to 100 calories of broccoli, but these foods have drastically different effects on the body. White bread goes through your digestive track almost effortlessly (except for it’s pro-inflammatory effects… but that’s another story), but the high fiber content of broccoli makes it much more intensive to break down. The overall caloric impact between these foods can be significant, and add up!
“Calories Out” – Potential Factors
How much muscle do you have?
Muscle tissue is “expensive”, meaning it requires caloric energy to maintain. Each pound of muscle tissue you have burns about 6-10 calories per day. Even fat, in the form of adipose tissue, requires energy to maintain, but it’s only about a 1/3 as calorically demanding as muscle mass. By simply having more muscle, your metabolic rate will be increased, and you’ll expend more calories at rest. However, the majority of the calories you burn from having that muscle is by actually using it!
How much are you actively/passively exercising?
Obviously, moving expends energy. Actively engaging in exercise tends to be efficient at burning a lot of energy in that short period, but passive exercise (ex. standing, walking around or fidgeting) tends to burn significantly more energy throughout the day. Here’s a quick tangent about passive exercise (also known as NEAT)..
Non-Exercise Activity Thermogenesis (NEAT)
NEAT is essentially just the amount of energy you are expending during non-intentional exercise. Interestingly enough, most of the calories burned throughout the day aren’t from our traditional workouts, but from the sum of all our passive movements! Implementing habitual changes (ex. standing vs. sitting or going on frequent walks) to increase your NEAT is a far more effective fat-loss tool than extending your scheduled workouts. Stay tuned for ways to increase NEAT later on in this article.
What type of exercise are you doing?
Low to moderate intensity steady state cardio may expend the most amount of energy during that session compared to other forms of exercise, but that doesn’t make it the most “efficient” form of exercise for fat loss.
Resistance training (ie. weight lifting, bodyweight training) has a much higher long-term metabolic effect than steady-state cardio, so you’ll expend more energy overall in the long run. The same goes for high-intensity interval training. Additionally, by investing in a form of exercise that will add muscle mass to your body, your metabolic rate will continue to go up, which will make your total caloric expenditure also increase.
Workout programming is also factors into the equation. A well-programmed resistance training program will force your body to consistently adapt, which will enable an advantageous long-term metabolic trend. Contrarily, steady state cardio tends to do the opposite. Over time, your body will adapt to the repetitive stimulus, and your metabolism will slow down to adapt and preserve fat tissue (not good!).
Hormones: A Variable That Affects Both “Calories-In” AND “Calories Out”
This is where things become more complex and less under our direct conscious control.
Hormones are key chemical messengers in the body, branching out from the endocrine system. The endocrine system is responsible for the regulation of our heart rate, metabolism, energy utilization, growth & development, and more. Keeping your hormones well-balanced is essential for optimal bodily function.
There are several hormones that play a significant role in how many calories you take in, how many calories you burn, and how those calories are allocated (stored as fat, expended as fuel, or synthesized as muscle tissue). The excretion of hormones can affect your appetite, hunger levels, or eating behavior, which can indirectly increase or decrease the total number of calories that are taken in.
Here are some of the common hormones that are influential in the “calories in vs. calories out” equation:
Leptin
This hormone is primarily secreted in your fat cells to decrease hunger. It works by telling your hypothalamus that it has enough fat, so you don’t need to eat. If leptin is functioning correctly (more on that in a minute), there should also be metabolic boosting effects to expend the excess stored energy (body fat).
There is a strong relationship between the number of fat cells you have and the amount of leptin that is secreted. In other words, the more fat you have, the less hungry you will be. However, as fat mass increases and obesity worsens, this hormone (and ghrelin as well) and it’s signal is negatively impacted, creating hormonal imbalances.
Once a considerable amount of fat has accumulated, leptin resistance can develop. This means that you can have a lot of fat that is secreting a lot of leptin, but it doesn’t work correctly to decrease your appetite! This can create a negative feedback loop that makes matters worse: Eat more. Hunger doesn’t disappear. Eat even more. Gain more fat cells. And so on…
On the contrary, if levels of body fat have gotten very low (this may apply to bodybuilders or athletes), the opposite is true. Leptin levels can decrease so much that hunger is constant. Incorporating a carbohydrate “re-feed” periodically can boost leptin and mitigate this issue.
Ghrelin
Both ghrelin and leptin are secreted in other parts of the body (peripherally), but have direct effects on the brain (central nervous system). Normally, your stomach makes ghrelin when it’s physically empty, which signals your hypothalamus.
Ghrelin works similarly to leptin, but it has the opposite effect. It is secreted in the stomach to stimulate hunger. The more ghrelin that is secreted, the more hungry you will be!
Insulin
Insulin is the hormone that is responsible for facilitating the conversion of glucose into usable energy. It’s also fundamental in the regulation of blood sugar in the body. This is where hunger can be indirectly affected.
Each time carbohydrates, or even protein, are consumed, insulin is summoned to shuttle the available glucose to where it needs to go. If your body is sensitive to insulin (this is ideal), less insulin is required for the same effect. Depending on your insulin sensitivity, glucose will either be stored as glycogen or as adipose fat tissue.
Insulin does not directly stimulate hunger. However, it can do so indirectly. When blood sugar drops after an initial spike, ghrelin is produced when insulin is low. This increase in ghrelin production can increase hunger levels (at least temporarily). Additionally, since insulin resistance and leptin resistance are closely tied, hunger can be triggered if glucose is poorly utilized.
If you want to find out more, I wrote an article on insulin and what you can do to optimize your energy with the powerful hormone.
There are a myriad of other factors that can indirectly contribute to these hormones, including sleep and the health of your microbiome. Many of these hormonal effects are not yet fully understood, but we know for sure that they play a crucial role in the utilization and expenditure of energy!
Common Mistakes
Imprecise Estimation of Calories In vs. Calories Out
As I explained in this article, the calories in vs. calories out equation is pretty complex. One of the most common issues people have with gaining/losing weight is that people are drastically under/over-estimating how much energy they are taking in or expending.
There are numerous factors than can lead to this imprecise estimation. Even if your food measurement is on point, food labels tend to be inaccurate, especially for multi-ingredient packaged foods. This can cause your calorie summation to stray from your target goal.
Just because absolute accuracy is almost impossible doesn’t mean that tracking is a waste of time! Calorie tracking can still give you a relatively consistent baseline of where to start. If you’re new to dieting, calorie counting becomes particularly important because it creates awareness for what (and how much) you’re putting into your body.
Long Term Sustainability
The problem with calorie tracking, and other health-focused practices, is the ability to adhere to them in the long-term. Since it requires a considerable amount of effort, sustainability can be tiresome. This is where short-term discipline and long-term habit formation comes into play.
Initially, some self discipline is needed to leave your comfort zone and make life altering decisions, like monitoring the foods that you’re going to eat and consciously choosing different actions over others. Fortunately, over time, chronically forced decisions transition into habits.
Once habits start to form, these decisions no longer become conscious decisions, and hopefully become more automatic! Just like with brushing your teeth, once you do something every day for a while, it becomes habitual. The same methodology applies to opting for eggs for breakfast instead of a bagel or going for a walk after meals become. These habits can become second nature too!
Calories In vs. Calories Out are Dependent of Each Other
To further complicate the equation, its important to note that “calories in” and “calories out” are dependent variables. You can’t treat each of them as independent factors because if you influence one, the other one is affected indirectly!
For example, if you eat fewer calories for a period of time (calories in decreases), your body will begin to adjust, slow down your metabolism to adapt (calories out decreases), and set that as your new baseline. On the contrary, if you begin exercising more (calories out increases), your appetite will likely increase, and you’ll be inclined to eat more (calories in increases)!
This is why losing weight is so much work. You’re fighting the evolutionary signals that are in place to increase the chance of survival. The fact of the matter is: If you’re in an energy deficit, you will be hungry at times!
This a great example of why crash dieting doesn’t work in the long term. Drastically lowering your calories will result in short-term weight loss, but it’s not sustainable and you’ll find yourself in a hole that is even more difficult to escape. Crash diets can even compound on each other and matters a lot worse.
This is where the terms “Yo-Yo dieting” and “metabolic damage” come from. If you lower calories too much and too quickly, once you give in and increase calories, you’ll have a lower baseline than when you started, and you’ll actually gain weight! Fat-loss just became even more difficult, so metabolic boosting practices (ex. resistance training) are pretty much required.
The dependence of these variables helps reiterate the importance of treating the cause of the problem and not the symptoms. Let’s say your problem is being overweight. Instead of going head on and attacking the problem by unsustainably starving yourself, seek out the root cause: poor eating habits and a less-active lifestyle. By following an incremental step-by-step approach to change your eating habits and lifestyle for the better, you can combat the factors that got you there in the first place.!
Trust Your Body
Making these lifestyle changes can be scary at first. You may feel uncomfortable, your appetite and digestion may be all over the place, and your sleep might even be affected. These changes are all normal. Your body just needs to time to adjust and work itself out.
Once you correct some of these misdemeanors and develop some effective habits that set you on the right path towards your goals, your hormones will begin to auto regulate themselves, and then restoring your physiological energy balance will become a lot easier. It just takes some initial discipline, a plan, time, and patience!
Finding a Balance Effortlessly with a Healthy Lifestyle
Now that we’ve covered exactly why the “calories in vs. calories out” equation is so complex, the last thing we’d want is for you to feel confused and overwhelmed. Fortunately, the body is an intelligent biological being and it figures most of this out for us! The only thing we need to do is create a healthy environment for our vessel.
This is where diet and lifestyle changes come into play. By nourishing your body with whole, nutrient-dense, unprocessed foods, we give our bodies what they need to function properly. Making good food choices, including lots of protein, fibrous fruits and veggies, and minimal sugar, will keep you full for a fraction of the calories. This makes lowering your “calories in” variable effortless.
Prioritizing your diet over your activity level tends to be a more efficient use of time. Increasing your energy expenditure requires a lot more time and effort than cutting back slightly on the amount of energy (calories) that you’re taking in. The saying “You can’t out-train a bad diet” definitely holds true!
After establishing some solid dietary habits, it’s important to solidify a consistent and sustainable exercise routine. Moving regularly, as nature intended, supports our evolutionary biology, and enables our bodies to thrive physically.
Unfortunately, treating your body optimally isn’t nearly as easy as it sounds. When temptation presents itself, it can be tricky to say no! If you’ve dug yourself into a hole, a little bit of work may be needed to get out. Since you’re rewiring yourself, you might even need to ignore some of your brain’s signals telling you that you’re uncomfortable.
If your goal is create a caloric deficit and lose weight, focusing on speeding up your metabolism with resistance training is a great place to start. If you haven’t already, check out my article on how to intelligently develop a strength training plan that fits your goals. This is where you’ll see real impact.
Also, slowly forming habits to unconsciously increase your passive caloric expenditure will make creating a caloric deficit much more attainable! Here are a few simple practices that you can implement:
- Standing vs. sitting at your desk – Standing burns 2x as many calories as sitting. If you sit at a desk for hours each day, this profound difference can add up!
- Walk around during phone calls or meetings – Finding an excuse to move more is always a good idea. Your brain actually thrives from movement, so your creativity will also likely improve!
- Go for a walk every hour and after meals – Intermittent and frequent movement tells your body to mobilize stored energy to use as fuel, rather than to be stockpiled as fat. This is particularly important after meals because of its insulin sensitizing effects. If possible, going for 3 separate 10 minute walks is even better than going for a single 30 minute walk!
- Optional: Invest in a fitness tracker – Counting your steps is a great way to increase awareness of how much you’re actually moving each day. These trackers aren’t precise, but they can still be enlightening. The average American only walks ~4,000 steps each day… Striving for 7500+ steps/day is a great place to start!
Try to pick 1-2 of these practices to incorporate into your lifestyle. These practices may seem like a chore at first, but after doing them for a week or two, they’ll become effortless and habitual!
The complicated nature of “calories in vs. calories” out shouldn’t be intimidating. Now that you have a better understanding of the variables involved, you can use those tools to work towards your goals. Once you concentrate on including both active and passive exercise as a regular part of your routine and make smart dietary choices, the rest should take care of itself!
Fasting: A Worthwhile Tool?
Fasting, or time-restricted eating, obviously temporarily reduces your “calories in” (because you’re not eating!). By shortening your eating window to fewer hours of the day (ex. 8 hours fed, 16 hours fasted), unless you overeat considerably, it’s difficult to take in the same number of calories as in a conventional eating approach.
Fasting clearly works in the short term, but is it an effective long term solution? If so, it can be another powerful tool to put in your tool belt for the manipulation of your energy balance.
In addition to temporarily cutting back entirely on your caloric intake, fasting actually has a notable effect on your hormones. By restricting food, your body goes into a “fight or flight” mode to urge your body to find food in order to survive.
In the short -term, fasting tends to decrease leptin (suppress appetite) and increase ghrelin (stimulate appetite), which can temporarily cause spikes of hunger! This is an evolutionary mechanism to urge you to go find food! Don’t fret though, hunger pangs are no reason to panic.
Your body operates like a clock (partly due to your circadian rhythm), so hunger sensations will come and go, usually around normal meal times because of the cyclical excretion of these hunger hormones. This is why you tend to get hungry around your conventional breakfast, lunch, and dinner times. You’ll also notice, that if you skip a meal, you’ll be hungry for about an hour or so, but then that sensation should subside until your next meal time.
As you can see in the graph above, after a few days, your hormones will begin to re-regulate themselves, and you’ll adjust to a new eating schedule. Ghrelin levels gradually decrease to a lower baseline after a few days. This can help get re-balance your hormones and take back control of your appetite.
As a disclaimer, people respond to time-restricted eating differently. For some people, appetite is easy to control, energy levels are great, and it’s easy to adhere to! For others, the opposite is true and it may not fit your lifestyle. It doesn’t hurt to give it a shot!
Lastly, I wrote a short article to sum up the implications of fasting on the ability to eat large, satisfying meals. Check it out if you’d like!
Focus on What you Can Control!
As a final note, it’s important to remember that you can directly only control a few of these factors, so focus on those. It’s empowering to understand how the biology of your body functions, but try not to stress too much about about what it’s doing on a physiological level.
You can’t consciously control the excretion of hormones in your endocrine system and you can tell your brain to send the right messages to the rest of your body, but you can support the optimal functionality of these systems with smart lifestyle choices. The other factors that you can’t directly control will fall into place and change indirectly by implementing a healthy lifestyle!