Fat: The Central Macronutrient

In this article I will describe some basics of the bodies metabolization (how it gains energy) and will point out why fats are the cornerstone of a healthy, efficient diet (why fats are the central macronutrient).

Gaining energy from food

We humans, as organisms, eat, digest (break down) and metabolize (consume as energy) food for both energy (to fuel our bodies activity) and nutrition (for essential building blocks) needs. The body can fuel on all three macronutrients (proteins, carbohydrates and fats) for energy. However, the body has a couple main processes for metabolization, one for converting free fatty acids (fats turn into free fatty acids when they enter the bloodstream after digestion) into energy and one for converting glucose (carbohydrates turn into glucose when they enter the bloodstream after being digested) into energy. The first process is called Beta-Oxidation (metabolization of free fatty acids by body cells) and the second process is called Glycolysis (metabolization of glucose by body cells).

Proteins are primarily building blocks

Proteins can be used as fuel when the liver converts them to glucose and then be metabolized with Glycolysis. This is a costly process and the body only uses this route when a person either eats a diet very high in protein and low on carbohydrates and fats OR when we are starving (have little to nothing to eat) and our fat tissues (the stored version of fat) and glucogen (the stored version of glucose) reserves on our bodies are low. In the latter case, our bodies may engage in proteolysis (the process in which the body breaks down it’s own muscle tissue for protein) and use the gained protein for fuel. In the first scenario, the body is burning energy inefficiently and in the second, it is burning energy inefficiently as well as losing muscle mass. This makes it fairly obvious that proteins were not meant mainly as fuel (for energy), but more for providing essential building blocks.

Fat : Carbohydrate ratio

This leaves us with fats and carbohydrates to deliver the lion share of our energy needs. A question that arises is, how should we distribute the delivery of this energy between fats and carbohydrates. In other words:

What kind of a Fat : Carb ratio should we adopt?

The answer is, it depends. If my only goal is survival, it doesn’t matter very much, my body will gain energy just fine when I don’t pay attention to how much fat versus carbs I ingest.

If my goal is health and efficient energy metabolization, the question becomes much more relevant. Let’s further examine how carbs and fats provide us with energy and how these processes work in our bodies.

Energy yields

When we compare the two processes of fat and glucose metabolization (described earlier), we find that beta-oxidation has a much larger yield of energy than does glycolysis. On the flipside, glycolysis is much faster than beta-oxidation. Given these facts, it comes to no surprise that glucose provides the energy for activities and actions that are short-and-fast (quick-and-dirty fuel), whereas fats provide the solid background baseline of energy that can be used for slower, continual activities of the body.

Energy Efficiency

In efficient energy metabolization all fuel is used optimally and the metabolization processes are operating smoothly. Upon examining how our cells work, we find that a ratio higher in carbohydrates causes our metabolization to slow down and gain less energy. It also increases the likelihood that we gain weight and have mood swings (between hyperactivity and energetic lows). In order to understand why this happens, we have to dive a bit deeper into the cells’ metabolism.

As it turns out, in human beings (and other animals), some of the end products of Glycolysis as well as Beta-Oxidation can be further used by the mitachondria in our cells to generate more energy (Doug McGuff, 2010). This process is called the Citric Acid Cycle, requires oxygen, is much slower and yields about eight times as much energy as Glycolysis. Because this Citric Acid Cycle (CAC) is much slower than Glycolysis, the CAC can never keep up with the rate of Glycolysis. For this reason, it is KEY that the rate of Glycolysis is not continually high (Glycolysis can be lowered by providing the cells and body with less glucose). If this does not happen, the CAC will down-regulate the process of Glycolysis and the glucose will be forced back into the bloodstream.
This is literally how energy metabolism is slowed down and thus, less is energy is yielded for the bodies activities. The excess glucose will then be send for storage as too high levels of blood glucose are damaging to our arteries (more on that later in the article).


Checking the reserves

Excess glucose in the body can get stored as glucogen in the liver and the muscles. The capacity for glucogen stores lies somewhere between 200-400 grams(depending on the size of the human being). If more excess glucose is present in the body and the glucogen stores are full, the liver will convert it into triglycerides by a process called De Novo Lipogenesis (which means ‘new fat making’). These triglycerides will then get stored as fat tissue in fat cells (and this is how a ratio higher in carbs will lead to weight gain). This process of converting a carbohydrate into fat stores happens automatically for ethanol (alcohol) and fructose, hence the common term: beer belly. For this reason, it is wise to avoid high intake of alcohol and to fully eliminate all processed foods (as almost all of them contain added fructose ingredients).
What about fat stores? Well, we’ve all seen the capacity for fat storage…
Fat storage is certainly not limited to the following ranges, but these ranges are most common for people: between 10 and 20 kilograms.

One gram of glucogen is good for 4 calories, so at a maximum (400 grams), our glucogen stores can supply us with 1.600 calories. Wow, that isn’t a whole lot. For fats, one gram is good for 9 calories, so at a minimum (10.000 grams), our fat stores can supply us with 90.000 calories. Wow, 1.600 versus 90.000 calories of energy, quite a substantial difference. Obviously, glucogen stores are not a reliable source of energy storage and it were our fat stores that got our ancestors thru a rough winter with little food.

According to Doug McGuff (2010), the glucogen stores main tasks are providing sudden bursts of energy when we need it (this is why glucogen is stored in muscle tissue, readily available in sudden emergencies) (remember, glycolysis is faster than beta-oxidation) AND in order to keep blood glucose at the right level (this is why glucogen also is stored in the liver).

Preference of the bloodstream

Like I mentioned earlier, our bloodstreams require that blood glucose is within a certain range (at about 3.6-5.8 millimoles per liter, Wikipedia).
If blood glucose becomes too high or too low, it is damaging too our arteries, as well as other parts of our body that rely heavily on glucose (such as the brain). Meals high in carbohydrates will spike blood glucose levels and result in the necessity to bring those levels back to the normal ranges. To achieve this, insulin is released into the bloodstream and will promote the metabolization of glucose as well as the storage of fat.
As a consequence, any fat consumed together with a high carbohydrate meal will be stored, as clearing the glucose is a bigger priority (remember, glucose is metabolized faster by cells). In this way, the insulin triggered by the high-carb meal will promote glycolysis in our body cells. Unfortunately, the cell’s mitochondria cannot keep up with this (as CAC is much slower than Glycolysis) and the cell is stuck with a problem. This is especially the case when a person eats meals high in carbohydrates on a frequent basis. To solve this dilemma, the cell reduces it’s responsiveness to insulin by down-regulating it’s insulin receptor sensitivity as well as reducing the amount of insulin receptors on the cell. In the meantime, less glucose can enter the cells due to reduced responsiveness to insulin and the glucose has to go somewhere. So the body exercises some more De Novo Lipogenesis, it turns the excess glucose into fats, which will immediately get stored in the fat cell due to the high levels of insulin in the bloodstream. And if the person eats a lot of carbohydrates on a consistent basis, insulin levels will be high more frequently and this will make it impossible for the person to burn stored fat tissue for energy (as insulin makes sure it stays inside the fat cells). And this is why most people become fat, because they are misguided in nutrition (and not because they are lazy, exercise too little and eat too much).
However, not all people will become fat on a high-carb diet. The excess glucose needs to be either metabolized or converted to fat. The other strategy the body can use is to quickly fuel it all up when high blood glucose hits. This was mainly how a high-carb diet effected me, I got restless and hyperactive and my mind was always racing (the brain is a great outlet for using glucose). The energetic ups and downs of a high-carb diet ultimately stopped working for me.

Blood pressure to top it off

Because bringing blood glucose levels back to normal is a top priority for the body, it will also want to do anything it can to get the glucose either metabolized or stored quickly. One way by which this is accomplished is by narrowing the vessels of the bloodstream. There you have it, another factor that is damaging and stressful to the body: high blood pressure.

Unable to tap our reserves, we become carb-dependent

As our blood sugar levels are spiking up and down, our cells’ way of coping with this is to either spend all the fuel quickly with glycolysis and/or store the rest as body fat. It’s our bodies coping response to a stressful situation (being exposed to high blood glucose on a consistent basis). As a consequence the CAC can’t keep up and our bodies fail to achieve that nice, solid baseline of slow, sustaining energy.
With a deficient energy metabolism in our cells, we start craving more food. We eat the wrong foods and our condition worsens. We become more carb-dependent for energy as our cells become less and less responsive to insulin and our ability to tap into fat metabolism for energy get’s hampered. If you experience any problems from going for 8-10 hours without consuming calories (in the daytime), this is you.
Fats, on the other hand, don’t have any of these detrimental influences on insulin functioning and energy metabolism like carbs (when consumed in large amounts). They are metabolized more slowly and provide a solid baseline of energy.
Millions of years of living off of primarily animal fats has given us the great capacity to sustain stable energy levels thru-out the day. High-carb diets throw off our hormonal systems and the energy metabolization in our cells, it is incompatible with our biology. Returning back to the native human diet that has fat as the central macronutrient is key to regaining that solid baseline level of energy.

Fats serve two purposes, while proteins and carbs primarily serve one

At the start of this article I wrote that we eat food for energy as well as for essential building blocks for the body. Proteins are mainly ingested for their essential building blocks. Carbohydrates are mainly burned for energy as glucose. Fats on the other hand serve both as fuel, as well as providing essential building blocks. We already established that fats differ from carbs in that they provide a solid baseline of slow and sustainable energy, but fats are also used for many, many other purposes in repairing and renewing the body (for example, the membrames of cells are built largely out of fat).
To cut fats to a minimum in a diet is to lose that solid background of energy and be bound to the fluctuating energy high’s and low’s that high-carb eating brings. It also results in having less resources available for the bodies healing and renewal processes.
It would be akin to spending most of your money on rocket fuel for a race-car while shortening your budget on oil refreshments, check-ups, replacing old car parts, etc.
After a while, the car would start to get damaged and malfunction.

So what is the proper ratio?

For me, I set my ratio at about 3:1 (fats:carbs). This is not in grams, but in calories. As fats are more rich in calories, the ratio in grams is 1.33:1.
I find this ratio is complementary to our bodies requirements for fast energy in the form of glucose as well as the solid baseline energy gained from fats. The best fats to consume are saturated fats from healthy ruminants that have lived a good life and have gotten quality foods themselves, as well as mono unsaturated fats found in foods like avocado’s and olives. Eat healthy, fatty fish a couple times a week.
Limit nuts, seeds and avoid their oils, they are pro-inflammatory, these oils are processed foods and do not occur in the nature.
For carbs, stick to vegetables and not too much fruit (2-3 pieces a day is max).
I’m not a low-carb fanatic, I believe in a healthy macronutrient balance that is in alignment with how our bodies metabolism works. The traditional diet that is being recommended in today’s western society is simply ridiculously high in carbohydrates and includes processed foods that are disruptive to our bodies natural digestive system and metabolism. A paleo diet on the other hand, focuses on natural foods, includes substantial amounts of all the macronutrients and recognizes that the central macro for human beings is fat.

Eat well,
Edje Noh

PS: On a side-note, HIIT (high intensity interval training) stimulates CAC metabolization, whereas long, sustained sessions (over an hour) of intermediate exercise promotes will force that CAC will not be able to keep up with Glycolysis.
For more in-depth information about energy metabolization, check this great lecture by Doug McGuff MD, it’s a great resource:

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6 Responses to Fat: The Central Macronutrient

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