How our bodies process fuels
When we consume macro nutrients, our bodies go through a priority for dealing with them. This priority can be very useful in understanding how our bodies work and how to leverage it for losing weight.
Our bodies don’t like having an over-saturation of fuel in its blood at any time. It tightly manages the fuels so you don’t get into dangerous situations like hyperglycemia or blood glucose that is too high. But it also manages and controls other fuels like ketones (beta hydroxybutyrate or BHB levels) and fats (free fatty acids or FFA and triglycerides) to keep them under control and not over-saturate the blood with fuel.
It is like the engine of a car. You don’t want to give the engine too much fuel and blow it up. So the body controls the amount of fuels in the blood to ensure you don’t “blow up”. To do this, the body will address the most important (or potentially most dangerous) fuels first. It does this in a very logical way. In reverse order of storage capacity.
Here is a chart showing the breakdown of oxidative priority.
Modified Source: “Keto.” By Maria and Craig Emmerich
Original source: Oxidative Priority, Meal Frequency, and the Energy Economy of Food and Activity: Implications for Longevity, Obesity, and Cardiometabolic Disease, Sinclair, Bremer, etal, February 2017
The #1 oxidative priority is Alcohol because there is zero storage capacity for it. It makes sense that the body would address this first since it can’t store it anywhere and too high of blood alcohol means death.
The second oxidative priority is exogenous ketones. These are ketone salts that raise blood BHB levels. There isn’t a storage site for ketones either, so the body must deal with this before addressing other fuels. That is why exogenous ketones aren’t the best option when trying to lose weight. They displace fat oxidation keeping fat stored while it uses the exogenous ketones as fuel instead.
The third oxidative priority is protein. Protein is a bit different as there is a limited storage space for protein, but protein is not a good fuel source. It takes 5 ATP to turn protein into a fuel (glucose through gluconeogenesis) and another 2 ATP to burn in the mitochondria. Why would be body expend 7 ATP for something it can do for 2 ATP by just burning glucose or fat from your body? Protein is only really used as a fuel when other fuels (glucose and fat) are not present and it is forced to use protein. Protein gets preferentially used to stimulate muscle protein synthesis. It builds and repairs lean mass.
The next oxidative priority is carbohydrates. It has a moderate amount of storage capacity at 1,200 to 2,000 calories.
The last oxidative priority is fat. This makes sense as there is a theoretically unlimited storage capacity for fat. There are people with upwards of 400 pounds of stored body fat which represents 1.6 million calories.
Oxidative priority can help you understand what happens when you put certain fuels into your body. If you are drinking alcohol while eating carbs and fat, the carbs and fat will primarily go into storage while the body deals with the elevated alcohol.
To understand the power of oxidative priority take the case of an alcoholic. Alcoholics will have very low A1c levels (in the 4’s) no matter what they eat! If they eat tons of carbohydrates they will still have an A1c in the 4’s because the chronically elevated alcohol levels force the body to store all glucose while dealing with alcohol creating a low A1c. I am not recommending to become an alcoholic to lower you A1c level, quite the opposite actually.
So what does this mean and how can you leverage your bodies biology to lose weight?
If you avoid alcohol and exogenous ketones, get a just enough protein to support maintenance of lean mass (about 0.8 times your lean mass in pounds for grams of protein a day), limit the carbs and then reduce dietary fat a bit to force the body to use more stored body fat for fuel you will lose body fat. When you restrict carbs for long enough (4-6 weeks for most people) the body gets used to using fat as its primary fuel (keto adapted). This means it can burn body fat or dietary fat equally well. Eliminating other fuels and keeping dietary fat moderate allows the body to focus on body fat for fuel resulting in fat loss.
That is our bodies system for processing fuels coming in through the diet. Leverage it for improved results and body recomposition.
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