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Day one of your dieting phase? OK, time to jump start your metabolism.
Gouge my eyes out and punch me in the throat if I ever have to hear that again. The myths, the misnomers, and the general misunderstanding of human metabolism have run rampant through social media since inception.
Drink this to boost metabolism? No thanks.
Eat more of this to vastly increase metabolic rate? Probably not.
Do this exercise to burn pure belly fat? That’s going to be a big no.
Eat 12 meals a day to keep the furnace burning? Stop the madness.
The dynamics of human metabolism are immensely complex and almost impossible to nail down exact figures on outside of a research laboratory setting. Day to day fluctuations in a number of variables that influence metabolism can be enough to give you a full blown aneurism. However, taking a snapshot of someone’s metabolism in a specific moment and then understanding particular variables that cause that figure to increase or decrease can be quite valuable as a coach and a physique based athlete. The figures that will be discussed in this article will be: Total Daily Energy Expenditure, Resting Metabolic Rate or Basal Metabolic Rate (what most people refer to as their “metabolism”), the Thermic Effect of Food, Non-Exercise Activity Thermogenesis, and Exercise Activity Thermogenesis. We will also take a look at how these numbers can downregulate as we diet and discuss some strategies that we can utilize to keep our metabolism churning as the fat falls off.
Total Daily Energy Expenditure [TDEE]
As the name suggests, this figure is the summation of all of our other numbers added together and is a representation of how much energy (measured in kilocalories) you expend during a 24-hour window. To calculate this figure, you add up resting metabolic rate, the thermic effect of food, non-exercise activity thermogenesis [NEAT] and exercise activity thermogenesis [EAT]. Simple, easy, clean, and concise math right? Unfortunately, not so much. Arriving at exact numbers for each of these figures is, for all intents and purposes, impossible in the absence of massively expensive research equipment. Nonetheless, let’s see how we can best estimate these numbers and what factors cause them to increase or decrease in the scope of a fat loss diet.
Basal Metabolic Rate [BMR]
“I’m overweight because I have a slow metabolism”
We have all heard it and maybe even said it in naiver times, but when people refer to a “slow” or “fast” metabolism, BMR is the figure they are talking about. While they may not have a strong understanding of human physiology, most people would be right in saying that a “slow” metabolism can doom a fat loss phase. BMR accounts for 60-70% of your total daily energy expenditure so a downregulation in this number can most certainly be the death knell of your summer six pack dreams.
What is BMR? How does it change? How can I increase it? Why does it decrease? You’ve got questions, I’ve got answers.
Basal metabolic rate, by definition, is the amount of energy expended by the body at rest, per unit time (for this discussion we will use 24-hours as our unit time). An example of this might be, how many calories does my body utilize during a 24-hour bedridden Netflix binge? BMR is simply the amount energy required to maintain function of basic human processes like breathing, circulating blood, brain function, etc. There are quite a few formulas that will calculate this number for you but the two most commonly used would be the Harris-Benedict equation and the Katch-McArdle formula. The Harris-Benedict equation uses your height, weight, and age to estimate BMR while the Katch-Mcardle formula only uses a weight figure in the form of lean body mass (what you weigh with the exclusion of body fat).
Common denominator for both formulas? Weight.
While other hormonal factors may have downstream effects on BMR, aiming to manipulate those on a daily basis is missing the forest for the trees.
The single most effective way to increase your basal metabolic rate is to be larger or weigh more. Now, I know what you’re thinking. “I’m dieting and losing body fat, why on God’s green Earth would I want to weigh more?” Let me just say, I feel you on that one. A decrease in basal metabolic rate over the course of a diet is unavoidable as your weight/body size decrease (we won’t bother confusing ourselves even more by discussing how this number becomes even lower due to decreases in very metabolic organ tissues).
However, there is one way to fight the good fight and stick it to the metabolic downregulation man. You can increase or maintain as much lean body mass as possible over the course of a diet. Metabolic downregulation via losses in body fat are going to happen and are a foregone conclusion within the process. But, losing muscle mass along the way should be avoided at all costs. Luckily, I’ve got the recipe:
- 2 cups of progressive overload in your resistance training
- 4 tablespoons of ingesting a bare minimum of 0.8g/lb per day of high quality protein
- A handful of making sure that beautiful head of yours is sound asleep on a pillow for 8 hours a night
- And a sprinkle of managing daily stress as best as you can
Congratulations, you are now well on your way to fighting back against the dreaded “slow” metabolism.
Thermic Effect of Food
Have you ever sat down for Thanksgiving dinner or gone out to a Brazilian Steakhouse and noticed half way through the meal that you’ve got sweat beading down your forehead and pit stains like you just finished up a HIIT session on the Stairmaster? Well go ahead and forward all complaints to the thermic effect of food for that embarrassing moment.
The thermic effect of food is the amount of energy the body uses to digest, store, and use the food that you consume. The reason you were sweating like a pig in the previous example could be because you ate too much pig. Protein is the most thermic nutrient and it is estimated that you burn roughly 25% of the calories from protein just to break down, store, and utilize it. I can’t say I have ever come down with the Pop-Tart sweats but carbohydrates are the second most thermic nutrient. We burn roughly 10% of the total calories from carbohydrates in the digestion process. That 10% figure can increase for particularly fibrous form of carbohydrates like vegetables or whole grains and can decrease slightly for simpler forms of carbohydrates like candy or soda. Our least thermic macronutrient by far is fats or lipids. We burn a measly 2-3% of total calories from fat during digestion. So, if you’re looking to maximize the thermic effect of food in your diet, maybe throw a chicken breast in your coffee instead of butter.
While the thermic effect of food only accounts for roughly 10% of your total daily energy expenditure, it is still an important variable to look at and potentially optimize over the course of a fat loss phase. The first point that needs addressing is the decrease in thermic effect of food across the span of your diet. It is widely known that to avoid stagnation in fat loss, calories and macronutrients must be decreased on a semi-regular basis (Unless you’re my friend Taylor. Taylor once wrote about me in an article so I am returning the favor. Taylor also lost over 110 pounds without changing his calories once. We all want to be like Taylor). Thus, a decrease in thermic effect of food over the course of a diet is inevitable. You eat less food, your body uses less energy to digest that food. One strategy that may be prudent to implement, is maximizing this number from the get-go.
Maximizing the thermic effect of food of a diet means eating mostly our more thermic nutrients, proteins and carbohydrates, while incorporating just enough of our least thermic nutrient, dietary fat. Those in competitive physique sports do this on a daily basis without thinking about it. The standard “bodybuilder diet” is high in protein, high or moderate in carbohydrate depending on the season, and lower in dietary fats. It would be in your best interest to keep this ratio that favors protein then carbohydrates then fat over the entire course of your diet in order to maximize caloric burn via thermic effect.
But BRO, shouldn’t I switch to a high fat/low protein/extremely low carbohydrate ketogenic diet for the last few weeks of my fat loss phase to get rid of stubborn fat? No, no you should not.
Non-Exercise Activity Thermogenesis [NEAT]
When looking at metabolic downregulation as a result of extended dieting, the biggest dip we see is in non-exercise activity thermogenesis. NEAT can be defined and quantified as the amount of energy you use going through activities of daily life. It is the caloric burn as a result of common everyday tasks like walking the dog, taking the stairs, cleaning the house, and the rigors of a physically demanding job. Practically speaking, those with more physically demanding jobs will have a much easier time losing weight than their sedentary counterparts due to have higher NEAT. If you were to observe twin brothers, one a farmer and one a sedentary bank teller, the farmer would lose weight far quicker because he would have a much higher NEAT, even if all other variables were held constant. NEAT can be as low as a couple hundred calories in smaller, sedentary individual and well over one thousand calories in a larger individual who has a physically demanding job. It has even been shown in animal models that when energy availability is low, spontaneous activity decreases. Yes, the slugs became sluggish. Yes, I made that up. No, the study was not done on slugs.
Non-exercise activity thermogenesis decreases for a variety of reasons during a dieting phase. Some of these reasons are quite simple, some a bit more complex, and some still unknown. First off, over the course of a diet, you will weigh less and the activities of daily life that you usually perform will become less metabolically demanding as a result. Second, you’re going to subconsciously move around less. This is an autonomic response from your brain in an attempt to conserve energy. Your body senses low energy availability, decreased caloric intake and diminishing body fat stores, and thus cues you to move around less. What was once an easy 10,000 steps per day, becomes 5,000 without even noticing. If you’ve ever dieted for a bodybuilding show or gotten to very low body fat levels you have almost certainly felt this phenomenon. Stand up from my chair? No thanks, I’m good right here. The final feast or famine mechanism that your body activates is a bit more complex so let’s put it in layman’s terms, the body becomes more efficient at moving around. We call this gross mechanical efficiency and in times of reduced body weight, it skyrockets. There are a lot of hormonal and mechanistic theories for why this happens but the important takeaway is, the work that once burned 100 calories may only burn 70 or 80 now.
So, where’s the external validity here? How do we maximize NEAT in our daily lives?
If you’ve hung around the fitness world long enough, I am sure you have heard the old adage “Eat less and move more.” You see that move more part? Can you figure out what they were talking about? If you said NEAT, 5 points for Gryffindor. The more you perform any movement, and I quite literally mean any movement, from tapping your toe to standing up and doing the twist and shout, the higher your NEAT will be. Optimizing NEAT during a diet phase comes from moving around as much as possible. Here are some strategies that I utilize during successful dieting phases for both myself and clients:
- Institute a step count minimum. I like to start my clients off around 8,000-10,000 steps per day early on in the diet. If fat loss stagnates, we can easily increase that to 12,000-15,000 steps per day. Walking is a low intensity and low fatigue form of expending additional calories. It can also be a therapeutic and relaxing time where you can listen to music, be with your thoughts, or even invite a loved one with you and enjoy their company. I’ve seen step count minimums save both body compositions and relationships.
- Incorporate physical breaks at work. The modern work environment lends itself to a very sedentary lifestyle. As I sit here writing this, I can feel my NEAT tanking. BRB hitting ten push-ups. Ok, I’m back with a sweet pump and I increased my NEAT. Not funny? Fine, but it’s still a great way to increase your NEAT if you find yourself sitting all day. Take a walk, do some push-ups, hit a plank, do the Jen Selter squat challenge, just move around every 30 minutes or so.
- Park further away, take the stairs, ditch the drive through, etc. If you haven’t caught on by now, I am simply telling you to get up and move your tush. Am I making your life harder? Maybe. Am I making your abs and buns harder? Most certainly.
Exercise Activity Thermogenesis [EAT]
Exercise activity thermogenesis is what makes your athletes drop to their knees and scream “WHY COACH WHYYYYY?!?!” It is the caloric burn from exercise of the aerobic and anaerobic domain. When you summate the calories burned from your weight training session and your cardiorespiratory work, whether it be HIIT/LISS/MISS, you get exercise activity thermogenesis. Much like NEAT, EAT progressively decreases as you lose weight or fat during a diet. The two main reasons why it decreases align very similarly to those found in the section on NEAT: you weigh less and your body becomes more efficient at movement. Both of these factors lead to less calories burned per unit time aka your cardio that once burned 200 calories now only burns 175 because you are a leaner, meaner, more efficient human being. When you phrase it that way, it doesn’t sound all that bad. Wait, what? That means I have to do even more cardio? Hello darkness, my old friend.
The ways to combat a decrease in EAT are listed below:
The brevity of the above list indicates that there are no ways to fight back on this one. Even in laboratory settings where subjects were strapped up with weight vests that brought them back to their pre-diet weight, they STILL burned less calories than before the diet. No one said this dieting stuff would be easy and the takeaway for coaches/athletes here is that there is no hack, trick, or easy way out on this one. When fat loss stalls we revert back to the tried but true calories in versus calories out principle. If we want fat loss to continue, we need to manipulate one side of that equation. In the case of EAT, we have to jack up the cardio and increase the calories out. I believe Grammy nominated artist Future said it best, “there ain’t no way around it”.
A Depressing Conclusion
Front and center soldier as I give you one final address. It is with heavy heart that I inform you, the war on metabolic downregulation is a losing battle. We did everything we could to optimize our metabolism using every mechanism of physiology known to man. But, it is an inevitable conclusion of any fat loss phase that weight will be lost, moving around will decrease, movement will become less metabolically demanding, macros will be slashed, and cardio will indeed be “hardio.” But we rise up. We stand tall. We fight the good fight against the ebbs and flows of human physiology and we emerge on the other side bloodied, battered, and aesthetic af. Now, we recovery diet.
Let the massing chronicles begin.