The Law of Thermodynamics

Many people desire to achieve a body that is both healthy and one they are happy with. However, there is a lot of conflicting information around this topic, as well as companies selling hopes and dreams as opposed to fundamentals and realistic expectations. Too much of “do this and that” as opposed to “understand this and practice that.”  The purpose of this post is to create simplicity around the topic of exercise and nutrition. Therefore, I have chosen to use The Law of Thermodynamics as our reference point for the concepts I’ll be discussing here.

I introduced the Law of Thermodynamics because it is based off fact. It is a “law” after all, and whether you loved physics class or did not, the answer to any quiz, test, or question was always the answer that abided by those fundamental laws. So by using this as a building block for your foundation, you can continue to add knowledge without worrying whether or not it will make you question what you have learned previously. Now let’s get into what this law entails, and why it matters in the world of exercise and nutrition. The law was discovered back in 1850 and it said:

“Energy cannot be created or destroyed, only transferred or converted from one form to the other”

In thinking about our bodies, what we know as energy or the “unit” of energy is calories. Two things can happen with calories in the body. Conversion into either “work,” which is ultimately released as heat, or “storage” to be used later on as shown in the figure below. The human body is like a furnace that will convert the energy stored in food into heat and a variety of other biological processes. In fact, a majority of the energy consumed is lost or “converted” to heat. We all have something that we refer to as “our metabolism.” This is more accurately called our basal metabolic rate (BMR). We will go over more of this as well as how to calculate it in a separate article. For now, understand that the BMR is the number of calories required to maintain all basic life sustaining processes within the human body. Understanding this is critical towards determining an “energy balance” that will be conducive to your fitness goals.

So what does all of this mean? The law seems fairly straight-forward, but our focus is about exercise and nutrition. So how can we re-write this in a way that is more simple and applicable? By re-writing it as an energy balance equation depicted below. The law states that energy cannot be created nor destroyed. So when examining the equation below, the energy you take in must be converted into another form. But which “form” will be determined by whether the energy balance is positive or negative. Therefore, if you were to be in a positive energy balance, the energy will be converted to fat as “storage”. If the energy balance is negative, the energy will be converted to heat through various metabolic processes known as “work.”

“Energy balance = Energy input (Calories IN) – Energy output (Calories OUT)” 

Every day the human body requires a certain amount of energy to “keep the lights on,” and we described this as the BMR. Therefore, based off the above equation we are technically at a negative energy balance before our first bite of food. Let’s say that the average person’s BMR across ALL age groups is about 1,500 calories. In reality it is slightly lower for women, and slightly higher for men with the difference being explained by muscle mass and hormonal profile. However, remember that the BMR is just to keep the lights on, any additional processes will require more energy. Every footstep, every breath, and every movement of your hands “costs” more energy. Just imagine what lifting weights can do then.

Now, given that the BMR is 1,500 we would then have to consume about 1,500 calories just to have a “zeroed out” energy balance. So our final equation would appear like this:

“Energy balance = Energy input – (BMR + Work)”

We can say that if the average person were to consume 2000 calories right now then do absolutely nothing for the rest of the day, they would then have an equation that would look like:

“ + 500 calories = + 2000 – (1500 + 0) ”

Want to know what’s crazy? If that person did that routine 7 days in a row, or one week, They would be net positive 3500 calories which equates to about one pound. Unsurprisingly so, this is in fact what happens to many Americans. If this is not something that is paid attention to then within a year you would gain about 52 pounds. That is what the math shows us. Data from the CDC between the years 1999 to 2000 noted that the average American, including both males and females consume about 2100 calories. Studies today show that this number is up to about 2900 calories! Imagine what that net positive balance might be now and why we have an obesity epidemic in the USA.

So instead, let us fill in the last number of that equation (work) with a different number and see what it would look like with some adjustments.

“ – 200 calories = 2000 – (1500 + 700) ”

Now you are in a net negative balance. And that is just from some movement throughout the day. Add some exercise such as resistance training and you’ll create a much larger deficit. I mentioned resistance training earlier because it holds the greatest efficiency towards consuming calories (you quite literally do work and create heat at the same time). -200 calories would mean you would lose about 6000 calories in a month or about 1.7 pounds, also known as about 20 pounds in a year based off the numbers above. That might not seem like much but for those who are visual learners below I have shown how much fat that would actually be. Also remember, these are just examples, a greater negative balance can be created.

Though not the most aesthetically pleasing thing to look at, it gives insight on how transformational that can actually be in either direction.

A lot was discussed above so let’s recap in as clear and concise way as possible. If you are energy positive you will GAIN weight. If you are energy negative you will LOSE weight. That needs to be ingrained into your mind. There is no other way around that rule so remove any objections around that and accept it. I promise it will bring you so much less confusion and frustration around the concept of weight gain/loss. I believe that re-writing the law of thermodynamics into this equation makes the theory behind weight loss vs weight gain clearer, while also keeping the integrity of the law intact. All things living or not, comply with the first law of thermodynamics and human physiology is no exception to this. Therefore, whichever path you take towards your fitness journey, this concept will be at the core of it all.

As you have also seen above, calories move within the confines of that equation. The wonderful part about all of this is you can alter each of those factors to your advantage. I highly recommend following up on my post that discusses BMR as well as my post that discusses the role of muscle on BMR and weight loss. Yes, even the BMR can be altered despite whatever you have been told. BMR stands for basal metabolic rate which I said “keeps the lights on” right? Well, what would happen if you suddenly required more energy to keep the lights on because there is more of you? I want you to think about that because I’ll dive deeper into it in the future. If you just give me a little bit of your time here, I will show you just how incredible and adaptive the human body is. Whatever limits you think you have, short of true clinical disease, you are wrong.

My hope is that you leave here understanding that the idea of energy balance is incredibly simple. The physiologic and micro-processes behind it are wildly intricate and required many years of school along with countless hours of my own research to fully understand. This article is here to dilute all of that into only a few pages. Take the 5-10 minutes here to understand this concept as it is something that will actually follow you for your entire life. After all, no one beats the law of thermodynamics.

As always, if you have any questions on the topics discussed in these articles or anything else on this site, feel free to contact me. I feel like I can still say that given how small the community of people that come here is. Hopefully, the day will come where that is no longer feasible.