Your body is a very “BUSY” body: Why you don’t need to earn your food through exercise
Hi friends! This blog post is a contribution from my intern, Jennie. She is a current dietetic intern at the Massachusetts General Hospital finishing up her rotations to become a registered dietitian. Thank you, Jennie!
We love to complain about our metabolism. We love to say that our metabolism is not working fast enough, or “if only I had a better metabolism, I could eat ___.” Or “I didn’t workout today so I can’t eat ___.”
But, get this—we can still eat the cookies, the bread, the nachos, all those foods that we have labeled “off limits” because our bodies *need* fuel from calories (and oftentimes, more fuel than we realize).
There is not one food that can ruin our metabolism or instantly cause a change in weight. And a workout is not the largest energy consumer in our day to day lives. We can often have this very magical or catastrophic thinking when it comes to food, our weight, and metabolism.
Metabolism, when stripped down to its true definition, is the work that the body does in breaking down the food we eat and turning it into energy to allow us to live. For a “fast metabolism”, your body needs a lot of food. Consider it like a wood stove- in order for us to have a productive, hot fire burning, we need to keep consistently adding sizable logs. Twigs aren’t gonna cut it. A single log will burn out pretty quickly and going too long without adding a log is going to result in smoky embers...not a whole lot of flame, right? Just like a fire, our bodies need a lot of energy input in order to utilize that fuel efficiently. Our brain’s hypothalamus is like our internal thermostat that adjusts our metabolism based on our energy intake. If that intake drops or we are in an energy deficit, our body’s register that as if we were in a famine, and they sloooowww down our metabolism so we can survive with less energy. Of course, this doesn’t come without consequences! We observed in The Biggest Loser studies that participants who lost weight also experienced a pretty drastic decrease in their metabolism in response to the weight loss, demonstrating that their bodies were much less efficient at utilizing fuel. This suppressed metabolism is a survival adaptation and has lasting effects. When you think about it, our bodies are meant to keep us alive, and they do a pretty amazing job!!
A common misconception about energy needs comes back to intentional movement. Our world steeped in diet culture has taught us that our energy needs are mostly dependent on our movement. That if we have a big workout, we need to refuel, or conversely, that if we did not specifically set aside time for a workout, we need less energy. Get ready to be shocked…
Our energy needs depend MOSTLY on our BMR.
Ok cool, but what is BMR??
BMR is an abbreviation for Basal Metabolic Rate, simply meaning: the amount of energy needed to keep our bodies running at rest. This means subconscious tasks like breathing, circulating blood, keeping organ systems up and running, manufacturing enzymes, hormones and cells, and many other things that we may not even realize our bodies are doing throughout the day. That’s right. Even when we are sitting and watching Netflix for hours, our bodies need energy.
Sometimes BMR is used interchangeably with the term Resting Metabolic Rate (RMR). The only difference between the two, making RMR slightly higher, is that it includes the calories that are being burned at rest, in addition to the minimum number of calories needed for maintenance.
In fact, 60-70% of our daily energy intake is used for maintenance, or our RMR. Think about that number again. Reread it. Picture it. That is approximately 2/3rds of our daily intake being used just to keep us alive.
The next portion of our metabolism dedicates 20-32% of daily energy expenditure to physical activity. I bet many of us immediately associate the term “physical activity” to mean a workout, and while yes intentional movement is included in this category, so is the rest of our daily movements. I’m talking about getting out of bed, walking, brushing your teeth, getting dressed, washing the dishes, ANY movement during the day that requires energy.
The last portion of our metabolism allocates 8-10% of energy expenditure to the thermic effect of food. This means that energy is required to transform the food we have consumed into energy that the body can use for other tasks. Again, this is happening without us knowing. Who knew our bodies needed so much energy for tasks that we consistently overlook?
So if the thought of not needing to eat as much one day because there was no workout crosses your mind, remember how little our calorie needs actually depend on our workouts. Remember that workout or not, our bodies are working out every waking second of the day and THAT requires fuel.
So, with all of this in mind, remember that in actuality, we have very little control over how the energy we eat is used in our bodies. Remember that our brain, our organs, our blood are all things that we cannot live without.
And, that even if we aren’t feeling super hungry, our bodies still need food. If you’re struggling with a lack of appetite while the world is repeatedly pushing you outside of your comfort zone, check out my last post on low appetite days!
Fun fact: your brain uses 20% of your daily energy expenditure and requires the equivalent of 8-9 pieces of bread DAILY for the glucose it needs to operate.
Yes, your brain is 2% of your body weight…but remember all the things it does for us. We are nothing without a brain. When we don’t eat enough, we can feel some symptoms of our body and brain suffering, think:
Fatigue
Difficulty thinking or focusing
Consistent thoughts about food
Irritability
Poor memory
It is our job to feed our bodies, and in return, our bodies use energy where it is needed, allowing us to function.
The next time you think that lunch might not be necessary because you skipped your morning workout, or you just didn’t feel in the mood to move, remember that your brain is still keeping you active. That your blood is still coursing through your veins. That your legs are still taking you from place to place (even if it is just to the bathroom and back to the couch). Whether or not you are engaging in intentional movement, your body needs fuel. Like a lot of it. Like 3 meals and some snacks, or 4-5 snacks and a meal.
Things to think about
- Why am I engaging in this exercise?
o To feel good? Or….to earn my food?
o To relieve some stress? Or…to control my body?
o To move my body in a way that actually sounds good…or punishing?
I always love to think about the quote
“would you exercise the same way if you knew your body would not change?”
- Are you hungry?
o Eat! Our bodies are made to run on energy and to indicate when energy is low by sparking hunger!
§ Our hunger hormone ghrelin (or gremlin as I like to remember it because our tummy’s rumble when ready for food) is a helpful tool
Food for thought: if you had to go to the bathroom but felt like you just went, would you wait longer to go? The same question goes for food. If you are hungry, why wait to eat?
- What is making you question yourself?
o If it’s something you have seen on social media, unfollow the account
o If it is something you have learned over time, push yourself to examine why you believe it, If there is evidence to support it, and most importantly, how this belief serves YOU
o Talk to a friend or reach out for support!
- Ways to support a healthy metabolism
o Eat—aim to include a good balance of carbohydrates, healthy fat, and protein with each meal
o. Avoid dieting and restriction
o Sleep (I know this is a hard one, but trust me, it makes a difference)
o Engage in exercise or movement that you enjoy—if going on a run sounds like torture, try out a walk or some stretching
o Remember that food and exercise do not exist in a transactional, exchange-based system.
You do not need to earn or burn your food with exercise. Period.
Sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC124895/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4535334/
