Calories or Carbs: Which is more important for fat loss?

Calories or Carbs: Which is more important for fat loss?

How do I determine my calorie intake? 

Does it matter what percentage of my diet is made up of protein, carbs, and fats (macronutrients)?


I’m going to show you how.  But before that I’ll tell you the relative importance of total energy intake and the role of macronutrients in our body composition efforts.  You are much more likely to benefit from this program if you understand the reasoning underlying the creation of my approach.


First of all, it’s important to understand the value of our food from an energy and a nutrition perspective.  Food provides us with the raw materials and energy we need to carry on normal physiologic function.  Think of it as building a brick wall: we require the supplies necessary to construct the wall and the workers to actually build it.


However, food is not homogenous across all the available options.  A quick stroll through your local grocery store and a daring peak at the nutrition facts listed on the back of a handful of items, the vast nutrient diversity between them is apparent and somewhat striking.   Which of these ingredients are we to avoid?  What do these numbers even mean? We can focus on how to establish personal relevance on what these numbers mean for your efforts to lose body fat.


With such an influential role in human health it’s important to understand some basic nutritional terms before moving on.


Defined:  The chemical processes that make the energy contained in food available to the body.

Take Home:  Our metabolism converts food into the resources required for muscle activity, repair and remodeling, digestion and absorption functionality in the GI tract, synthesis of new substances in the cell, etc.


Energy in Food:


  • A calorie is defined as the energy it takes to raise the temperature of 1 gram of water by 1 degree Celsius.  Okay but what does that mean for us?
  • “Calorie” is simply how we quantify the amount of energy contained within a particular nutrient.

Take Home:  Through metabolic processes the body converts the energy contained in food into a universal “Energy Currency” that can be used in a variety of physiologic functions.  This form of capital is called – ATP (Adenosine Triphosphate).


Nutrient Composition of Food

  • Macronutrients
    • Defined: group of chemical compounds essential to supply energy for growth, metabolism, and other bodily functions.
    • Function: to provide energy.
    • Main Classifications: Protein, Carbohydrates, and Fats


  • Micronutrients
    • Defined: essential compounds  needed only in minimal amounts, not to serve as energy but to support a variety of biological functions.
    • Common Functions: enhance immune response, modulate free radical production and repair damaged DNA.
    • Main Classifications: Vitamins, Minerals, and phytonutrients.


Although the required amounts of macronutrients and micronutrients can vary markedly across individuals (depending on body size, age, activity level, pregnancy, fitness goals etc.), each essential nutrient is necessary in some capacity to avoid potential metabolic impairments.


Take Home:  macronutrients (protein, carbohydrates and fats) provide energy made available through metabolism, producing ATP, the body’s energy currency.  Micronutrients help facilitate the use of that energy.


Energy Balance.  Losing weight involves burning more calories than you consume. The general concept of energy balance is illustrated in Figure 1.



Figure 1.  Energy Balance.


Take Home: If you want to lose weight you will need to experience a “negative energy balance” (c), not all the time, but certainly when you sum up the energy equation over 5, 6 or even 7 days the aggregated environment must reflect a deficit.


Put simply, if you want to lose weight you will need to maintain a “negative energy balance” (c) overall.  Let’s put it this way, if you are supplying your body with sufficient calories to support daily function, there is no reason for your body to tap into internal fat stores specifically deposited for times of energy shortage.  In the long run, this simple reality is true regardless of how many carbohydrates are in your breakfast cereal or how much grass-fed butter is in your coffee.  So before you run to throw away all the carbohydrates in your pantry, understand that energy balance plays an essential role.


While it’s true that to lose weight you must burn more calories than you consume, it is possible to consume a surplus on some days, as long as you reduce caloric intake on other days to even things out. This is your chance to indulge now while still improving overall. #Winning.  Of course, taking advantage of this dietary “hack” first requires that you know your daily caloric needs.



So , WHAT should I eat? 


Although the pounds falling off the scale are dependent on total energy balance, where those loses originate (fat or muscle) can be influenced by the type of food you consume.  How then do we ensure we’re choosing foods that encourage FAT LOSS?

Here’s a good tid bit you may want to know; our body is predominantly reliant on carbohydrates or fat to meet daily energy requirements of simply living.  The magnitude of either nutrient being utilized will be determined by 2 primary factors:


1. Exercise (Intensity)

– Higher intensity exercise = more reliance on carbohydrates during exercise

– Lower intensity exercise = more reliance on fat during exercise/activity.


 2. Nutrition (Macronutrient composition)

– Limited availability of one substrate (carbs or fat) increases reliance on the other.

– Higher abundance of nutrient in the diet, higher utilization of that nutrient as fuel.


We have discussed exercises influence on weight loss last week in “Cardio vs. Strength Training”.  Let’s focus on dietary influence by using one of the classically proposed weight loss solutions. When people are referring to “low carbohydrate diets” they are trying to influence this metabolic balance by reducing one of the two dominant fuel sources – in many cases nearly eliminating carbohydrates from the diet.   By doing so we are increasing the dependency on other fuel substrates, primarily fat, to fuel energy requirements.


This metabolic shift happens for a number of reasons likely beyond the scope of this article but generally speaking can be categorically described by a couple dietary induced hormonal responses:


When we do not consume dietary carbohydrate, we experience a cascade of hormonal reactions that emphasize the utilization of fat for energy (potentially body fat).


– Reduced Insulin

– Increased Glucagon

– Increased Growth Hormone (mainly enhance free fatty acid release)


We will discuss the physiologic relevance of each of these hormones briefly in subsequent article “Dose Makes the Poison”.  For now, we simply need to understand that when we significantly reduce one macronutrient from the diet we see a natural increase in the utilization of the other, at least partly driven by these regulatory hormonal changes.


Okay great, so if we keep carbohydrates low enough (defined later) we will increase the utilization of body fat?


Not so fast, just because we’re metabolizing more fat doesn’t mean we are LOSING BODY FAT.  If we don’t pay attention to CALORIES and we naturally overcompensate for the reduction in carbohydrates with an increase of dietary fat – we see this dietary shift alone doesn’t necessarily imply the use of internal energy stores (i.e. body fat loss).


Although we’ve created an environment primed for FAT burning (say by reducing carbs 50%) – we’re simply providing our body with exogenous sources of dietary fat to utilize, consequently it doesn’t have to mobilize internal fat deposits.  This is where overall energy balance or the amount of calories you consume comes back into play.


Your choice between macronutrients can dictate FUEL USSAGE (carbs or fat) but it does not dictate from WHERE that fuel originates (internal or external sources of energy), CALORIES determine that.


Now some of the success experienced by the “Low Carb” approach is partly consequence of dietary exclusion as explained earlier.   To reiterate, let’s say we remove ALL sugar from your diet, because of the overwhelming prevalence of this nutrient across conventional food, you’ve dramatically eliminated your options to consume.  Additionally, low carbohydrate dieters appear to experience an improved ability to recognize and manage hunger signals in the absence of transient spikes in blood sugar.  Consequently, you will likely lose weight, at least partially due to the fact that you are now simply consuming less calories.


This is a point often missed, but because of this factor low carb diets can be incredibly effective at reducing body weight.  So if we can establish the right approach to carbohydrate intake & calorie restriction – we can create a perfect storm for BODY FAT LOSS.


Nutritional hierarchy of importance (for body fat loss):

– Calories IN. dictate from WHERE the fuel is being used.

– Macronutrient Composition of those calories (i.e. Low carb) –  dictate what TYPE of fuel is being used

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