F*ck Your Fitness Tracker
There is a common misconception that fitness is defined by how active you are, or how many calories you burn. With the advent of fitness trackers and smartwatches, counting one’s steps and daily caloric burn has become a tangible, methodical way of “scoring” fitness. More steps = more active = more fit. Right? Well, maybe not.
The idea that more activity results in burning more calories is known as the Additive Model of Energy Expenditure. This model operates off of the belief that physical activity is the most important means of expending energy. Move more, burn more, lose more → the message that has been repeated and reprinted throughout the fitness industry, by trainers, coaches, and even nutritionists. Weight loss is often approached as the simple matter of energy in < energy out. If this were true, then moving more and not eating as much would always result in weight loss, and the five boot camp classes you take a week would be having their desired effect. So what’s going on when someone is getting their ass kicked in the gym 4 to 5 times per week and restricting calories but not losing weight?
Energy Expenditure itself is the key to understanding the fitness puzzle, but it’s not as simple as the above model suggests. More and more studies are showing that our body’s metabolism produces a finite amount of energy in a given day. This is called the Constrained Model of Energy Expenditure. Without going into too much detail, a fairly recent scientific study showed that we burn the same amount of calories a day whether we walk 10,000 steps or 20,000 steps. Instead of burning more energy, your body simply redirects energy from other biological functions to meet the increased activity demand. This is vastly important because this shows that our metabolisms have an upper limit for energy expenditure, meaning that more activity is not necessarily a good thing.
Wait, what? Let’s break this down. The brain uses energy in three distinct ways. (1) Vital Functions, (2) Physical Activity and Stress, and (3) Tissue Recovery and Adaptation. A hierarchy exists within these three categories that ultimately dictates where the energy your body produces gets distributed.
Your Vital Functions are the first tier in the hierarchy. Your brain will never sacrifice fueling your daily biological functions (aka heart, lungs, brain - organs that are vital to your survival). This is fairly straightforward and obviously a good thing - no matter what shit you throw at your body, it will fight to keep you alive.
The second tier in the hierarchy is your Physical Activity and Stress. Note that this is ONE category. Your body does not differentiate between the stress caused by your workouts and the stress caused by every other facet of your life - work, relationships, family, etc. When faced with a stressful situation at work, your body responds much like it would if you were participating in a vigorous workout. Your sympathetic nervous system function kicks into overdrive (think fight or flight). Various stress hormones are released into the bloodstream, blood pressure increases, and your brain start working to mobilize energy stores. This Stress Response is a key component to training, and it’s why people that are more trained start to sweat sooner into their workouts than those that are untrained. Their bodies have been conditioned to shift into the stress response sooner. In other words, they’re ready to GO.
What happens when the thing that is stressing you out doesn’t require you to fight or flight? Let’s use the classic example of getting stuck in traffic. One second you’re flying down the highway on the way to work and the next, BAM. All red lights, bumper to bumper traffic. Your heart rate skyrockets and you start to sweat. Fuck. What you may not realize is your increased heart rate and sudden sweatiness indicates the activation of your body’s stress response. Your brain immediately starts mobilizing energy stores in order to fuel your fight or flight response - except you’re not actually going anywhere. When the traffic start moving again and you get to work (the stressful situation now dissipated), your body has to put back all of the energy stores it just mobilized. Sounds harmless, but from an energy standpoint this is very costly.
Think of it this way - you’re told to move a pile of heavy rocks from Point A to Point B. Then, when you’re all finished, you’re told to move everything back from Point B to Point A. Besides being pissed off, you’re tired. This is what your body does anytime your stress response is initiated. Although the fatigue isn’t physically tangible, your body has used precious energy from its finite stores to respond to the stressful situation.
In the same way, busting ass to get 10,000 steps each day costs you energy as well - maybe energy that you don’t have. Fueling your physical activity is the second most important thing to your brain. But again, forcing your body to fuel mindless physical activity simply redirects energy expenditure away from the third tier of the hierarchy.
Tissue Recovery and Adaptation is the third tier in your body’s energy expenditure hierarchy. This means that recovery, aka improving your fitness or losing fat/gaining muscle, is your brain’s last priority. Wait a second. Doesn’t recovery mean things like rolling out, eating the right foods, getting enough sleep, blah blah blah? Well yes, in a literal sense, but it means a bit more from a physiological perspective. Your body needs to have energy available to repair cells and rebuild muscle in order to facilitate structural, functional, and neuromuscular adaptations. Remember, your metabolism can only produce a finite amount of energy each day, no matter how much food you eat or sleep you get. So what happens when you use up all of your energy with physical activity and stress? There’s nothing left over for recovery and repair.
This is called Recovery Debt. Basically, there is more stress being placed on your cells and tissues from training and life than there is energy available to repair and rebuild them. You’re busting ass in the gym day after day but no adaptations are taking place. Simply put, your body isn’t changing (whether that means losing fat, gaining muscles, getting stronger, etc.). And where do our minds go when this happens? “I must not be doing enough.” So we schedule an extra workout or two and fight to get 20,000 steps, thinking that if 10,000 is good, 20,000 must be better. The kicker is, instead of fixing anything, you’re just driving your body further and further into Recovery Debt. The harder and longer you move, the more energy your brain has to redistribute to working muscles and other tissues. People are spending so much time and energy on training and dealing with the stress of daily life that there simply isn’t enough energy left over to go towards rebuilding and repairing the body. At some point, your body will physically be unable to keep up.
This is a total shift in the “more is better” mindset. Improving your fitness does not come from how much work you do in the gym or how active/stressed you are outside of the gym. Instead, it comes from the process of rebuilding and repairing from your workouts (not the workouts themselves) and your ability to manage the stress of daily life.
If you’re someone with a stressful work and/or home life, but still want to reap the benefits of an active lifestyle, be aware of how you distribute your energy stores. Reconsider using your Fitbit or Apple watch with the goal of hitting 10,000 steps everyday when you spend most of the day in a stressed state. Your energy is better spent in the gym and recovering from your workout versus taking the stairs instead of the elevator. In the same way, be aware of how often your stress response gets activated and what your triggers are. Your brain is only going to devote energy to building bigger and stronger tissues when there is enough left over after basic metabolic needs and physical activity/stress demands are met. Finding ways to 1) engage in more purposeful exercise (versus mindless activity) and 2) mitigate your life stress will lead to more energy available for recovery, allowing your to change your body composition and reach your fitness goals.
Your body has a finite amount of energy available each day
Your energy stores get distributed to three categories: 1) Vital Functions 2) Physical Activity and Stress and 3) Tissue Recovery and Adaptation
Your fitness will only improve when there is enough energy left for recovery and adaptation aka building bigger and stronger muscles and losing body fat
Engaging in purposeful exercise and managing life stress will help you reach your fitness goals in the long run!
Questions? Comments? Reach out!
Want more knowledge? Check out the podcast below from Sigma Nutrition featuring the author of the scientific study linked above.