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OVERVIEW OF THE HUMAN METABOLISM




         

 The metabolism can be simplified and broken down into two distinct phases that occur simultaneously around the clock where one phase becomes predominant over the other. When there is a predominant storing or building up of energy in the body this will naturally occur during a digestive and or resting phase; termed the Prandial Phase. 

Conversely, when we are more active and food intake is lower then we enter into a Post-Prandial Phase. Just remember that both of these phases are always occurring and whatever phase we spend more time in regularly will ultimately dictate where the scale goes and how our body will compose itself. 



PHASES OF METABOLISM:




CATABOLISM


*Releasing energy from the body (e.g. burning fat)

*Involves increased calorie burn or expenditure

*Involves decreased calorie or energy expenditure

*Creates weight loss

*Signaled by stress and fight or flight response




ANABOLISM


*Storing of energy in the body (e.g. storing fat)

*Turns on immunity, digestion, and reproduction

*Creates weight gain

*Signaled by relaxation, sleep, resting, or light activity



               Next, because energy expenditure isn’t entirely understood and promoted consistently across various media platforms in this day and age, there is an overreaction towards the anabolism side of the equation with food tracking apps and discussion, and what have you. With less focus complementing food tracking measures and looking at how energy is truly expended according to science, a big piece of the puzzle is missing so you can understand the function, application, and limitations of the entire energy distribution model.



THE 4 COMPONENTS OF CALORIE BURN:



         RMR + TEF + NEAT + EXERCISE= TOTAL CALORIE BURN OR EXPENDITURE




#1-RESTING METABOLIC RATE (RMR)


Your resting metabolic rate is the amount of energy required to sustain life and fuel basic biological functions, such as breathing and respiration, temperature regulation, blinking, cognitive function, low-level muscle activity or tone, heart rate, sodium-potassium pump, and several more. Years ago, it was thought that both the brain and liver contributed upwards of a thousand calories per day in energy burn to perform all of their various activities which are essential to our survival. This runs contrary to what you see regularly advocated in the mainstream, with false claims of muscle mass being the main RMR contributor. It’s not even close. Muscle does matter and this is especially true with the “afterburn” that is created during the recovery process after a grueling workout. 

However, it’s important to distinguish active versus passive contributions of energy when it comes to muscle mass. Calories expended during a workout and recovery from the workout would be active. 

This number far outweighs what muscle does passively, which is where most of the claims are made. Fat is almost as active of a tissue as muscle at rest, as it produces various hormones and certain fat stores such as brown fat can burn energy just like muscle itself.  

RMR (resting metabolic rate) can contribute anywhere from 50-70% of our total energy burn per day depending on the other three components. RMR accounts for the biggest piece of the pie with exercise coming in second on days we train hard, unless the duration and intensity of exercise sessions are extraordinary. Practically speaking, there are a few things you or your clients can do to ensure that RMR levels are optimized or remain normal during periods of dieting. First, calorie levels should NEVER drop below RMR levels.



#2-TEF (THERMIC EFFECT OF FOOD)


TEF is a technical term for the amount of calories we burn from the food we eat. More specifically, it’s the amount of energy required to transport, digest, absorb, and utilize the food we eat in our body. 

You will also hear acronyms such as; DIT (Dietary Induced Thermogenesis) and SDA (Specific Dynamic Action) which mean the same thing. Scientists like to break down TEF into two components; The Regulatory and Obligatory Components. Knowing this information is not essential by any means, and I’m just disclosing it to be thorough. The Obligatory portion is the part involving the energy necessary for digestion, absorption, and metabolizing the food. The Regulatory is the part related to energy being lost as heat. TEF is a relatively small number compared to the other components and we shouldn’t concern ourselves very much here because it makes up such a small portion of total energy burn. TEF sits around 10%. What’s important here is that you check off a couple of things you or your clients should be doing to get the most out of TEF and then be done with it and focus more effort on the things that matter most, which I will cover here shortly.

The two main things that affect TEF the most according to current research are how much lean mass you carry, as well as the composition or makeup of your meal. The more of each you have, the longer you will be processing the food and burning energy. But please keep in mind that this is a small number in the grand scheme of things, but could no doubt add up and amount to legitimate fat loss and results over the long term. Here is a quick chart breakdown of the TEF for all sources of available substrate energy.



Fat: 0–3% of calories consumed 

Carbohydrates: 5–10% of calories consumed 

Protein: 20–30% of calories consumed 

Alcohol: 40% of calories consumed


One analysis reported that, while protein was the only significant determinant of the total TEF, every 1% increase in calories from protein was associated with a mere 0.22% increase in the total TEF. Based on these findings, if you were to double your protein intake from 15% to 30%, your daily TEF would increase by only 3.3%. So for each 2,000 kcal you consume (a number that might represent your total daily needs), you’d be spending an additional 66 kcal — a number easily offset by one small apple or a handful of potato chips. 1 So as you can see it is very clear that eating protein directly will burn very few extra calories, and not contribute to fat and weight loss, or a handful of potato chips. 1 So as you can see it is very clear that eating protein directly will burn very few extra calories, and not contribute to fat and weight loss.


However, research has shown that protein consumption can have indirect effects on food intake which is powerful information. The higher TEF from protein may promote greater fullness so people don’t eat as much. One study in lean women found that greater 24-hour periods of TEF resulted in greater fullness and less food consumption. 5 Moreover, for the effect of more protein increasing fullness levels to take place, there has to be an intake of protein of at least 20%. I don’t think anyone has to worry here. Lastly, eating protein may also promote satiety by increasing the rate of intestinal gluconeogenesis (IGNG) — the rate of glucose production within intestinal cells. Currently, only rodent studies exist to suggest that IGNG is a key signal to the brain about energy homeostasis, but important enzymes involved in gluconeogenesis have been found in the small intestine of humans, suggesting that it may also take place within us. 1


Finally, amino acids may promote satiety by directly affecting the brain. Specifically, they appear to activate mTOR and suppress AMPK within hypothalamic and arcuate nucleus neurons. The branched-chain amino acid (BCAA) leucine appears to be particularly satiating, and can reduce food intake when directly injected into the brains of rodents. 1




On a final note, when you look at the grand body of research, no macronutrient deserves precedence over the other as they all work synergistically in the body to deliver energy and regulate various functions. As you will see soon, carbohydrates and fats also play a role in feeling full and regulating appetite just like protein.






#3-NEAT


NEAT is referred to as Non-Exercise Activity Thermogenesis. Fancy talk for any type of activity that isn’t exercise which burns calories. Examples include but are not limited to; fidgeting, pacing, walking, working outside, and so forth. Although the number of calories you can burn from this type of activity is severely limited compared to the other areas of calorie burn, it can add up, and much more so than TEF.

According to one study, NEAT can contribute up to 350 extra calories burned per day. That’s one extra pound per month, or 12 lbs. per year. 2 Another indirect area where NEAT can support weight loss and may be more powerful than the actual calories it burns per day is its effect on appetite and hunger signals. Research has shown that a lack of walking can disrupt hunger signals leading to increased appetite and potential weight gain. That’s powerful stuff. The body was meant to move, and this physical response is a testament to that fact.

Moreover, a study by Ledochowski et. al 2015 analyzed the effects of a 15-minute walk at moderate intensity and found that the walk did indeed reduce the cravings for sugary snacks. The investigation also falls in line with at least a half dozen studies that showed walking can reduce the urge to consume high-calorie snack foods. 3



#4-EXERCISE


Exercise for fat loss will be performed through four different types in a hierarchy-type fashion. 4  

As it relates to total energy expenditure, exercise can contribute anywhere from 0 to 50% of total daily calorie burn. Years ago, a brilliant researcher by the name of Lyle Mcdonald shared information that after you expend 1000 calories per day through exercise the body will begin to fight back and slow energy burn. Contemporary research also supports a constrained or limited daily energy expenditure in humans, although the procedures researchers used in these studies were admittedly inaccurate, among other things (i.e. overestimating metabolic reduction and adaption from dieting, and physical exercise contribution to total daily expenditure). 5 The 1000-calorie per day rule is a great one to live by because it’s pretty realistic and gives a good standard to support fat and weight loss efforts without overtraining.


SCIENTIFIC REFERENCES:

#3-Ledochowski L, Ruedl G, Taylor AH, Kopp M (2015) Acute Effects of Brisk Walking on Sugary Snack Cravings in Overweight People, Affect and Responses to a Manipulated Stress Situation and a Sugary Snack Cue: A Crossover Study. PLoS ONE 10(3): e0119278. doi:10.1371/journal.pone.0119278

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