Oxidative priority… it’s critical to understanding how fat loss works!
In this article, you will learn how your body uses various fuels (with some cool diagrams and examples).
These “secrets” are central to our systems that have helped so many people optimise their diet and achieve their fat loss goals.
This info will help you to troubleshoot your fat loss journey when you get stuck, as many people often do.
What is oxidative priority?
Oxidative priority is simply the order in which you tend to burn the fuels available to your body (i.e. alcohol, ketones, glucose, protein and fat).
Imagine if you poured crude oil on the ground, poured petrol on top of it, and lit a match. The petrol would burn off quickly while the oil may not even ignite. Oil burns slowly, while petrol burns rapidly.
Volatile fuels like gas are hard to store. By contrast, it’s much easier to store large amounts of energy as unrefined crude oil. The more we refine these fuels, the easier they are to burn. Similarly, the degree of refining and the macronutrient profile of foods you eat makes the different fuel sources behave differently in your body.
The fact that different macronutrients are harder to convert to usable energy and there are more losses in their conversion is a highly underappreciated food parameter that goes by several names including the thermic effect of food, dietary-induced thermogenesis or the specific dynamic action of food.
Most of us do not overeat protein because it is so satiating. It is more difficult for our body to convert protein to ATP, so it is a poor source of energy for everyday use. Your appetite for high protein foods shuts down once you’ve had enough.
So, our two remaining major fuel sources are carbs and fat. While your body likes to maintain some glucose in your bloodstream, if you have too much, you won’t burn the fat in your blood.
Because you can only store about 5 g of glucose in your blood (about a teaspoon’s worth), a little dietary carbohydrate can quickly change your blood sugar levels (particularly if your fat stores are already full so you can’t easily absorb the excess energy from your diet).
While we can convert sugar to fat (via de novo lipogenesis), most of the time it’s the fat in our diet that is stored because your body tries to burn off the glucose first and any leftover dietary fat can easily be stored.
It’s not necessarily that fat is a better fuel source than carbs, but it’s the glucose that will show up in your bloodstream and register on your blood glucose meter after you eat. Glucose essentially ‘floats on top’ of the fat in your bloodstream as well as your adipose tissue. While we always burning a mixture of the available fuels, the body prioritises oxidation of the more volatile fuels first.
So, to access your body fat, you need to deplete both the excess glucose and excess fat from your blood first.
In your body, your fuel tanks are separate but interconnected. As you deplete the glucose in your blood, it will be refilled from the glycogen stores in your liver (note: glycogen is just the fancy name for the storage form of glucose). As liver glycogen starts to be depleted, your body will turn to the fat in your blood, and then finally, your body fat.
You can think of your available fuels as though they are stacked up on top of each other (as shown below). So, when you measure blood glucose, you are not just measuring the sugar in your blood. You are measuring all the fuels stacked up in your body.
|glycogen in liver and muscle|
|free fatty acids in your blood|
If you want to get a bit nerdier, the table below shows more detail in terms of:
- oxidative priority,
- approximate capacity to store the various fuels, and
- their thermic effect.
|Alcohol||Ketones||Excess protein||Glucose||Fatty acids||Body fat|
|Use||Energy||Energy||Energy & excretion||Energy||Energy||Storage|
|Capacity (calories)||20||20||–||1200 – 2000||150||40,000 – 500,000|
|Thermic effect||15%||3%||20 – 35%||5 – 15%||3 – 15%||3 – 15%|
What does this mean for you?
- You have very little room to store alcohol or ketones. They are more volatile than the other fuels, so they have to be used as the highest priority.
- Most of the protein you eat is used for muscle protein synthesis (MPS) and other critical bodily functions. While ‘excess protein’ not used in MPS can be converted to energy (ATP), this usually only happens when you are not eating enough carbs and fat to provide adequate energy, so your body turns to the protein in your diet or the protein on your body (i.e. muscles).
- Excess protein (i.e. that is not required for muscle repair and other bodily functions) can be excreted in the urine (i.e. it is not used for energy). Again, this is rare in people with healthy kidneys because. A little bit of “labile protein” circulates in your bloodstream, but not much.
- Protein has the highest thermic effect (i.e. 20 to 35% of energy is lost in the conversion to usable energy), so your body has to work hard to convert it to usable energy. We don’t usually consume ‘excess protein’ and would prefer to get energy from fat and/or carbs, so higher protein foods tend to be more satiating.
- Your body has some capacity to store glucose in the liver, blood and muscle, but not a lot compared to your body fat stores.
- If you don’t consume a lot of carbohydrates, your body will work to keep your glycogen stores topped up by converting protein to glucose (through gluconeogenesis), so you always have some when you need it.
- You have some fatty acids in your bloodstream to use for fuel but a very large capacity to store excess energy that you do not use.
- The amount of energy your liver drip feeds into your bloodstream from day to day is tiny compared to the amount of energy you store as fat.
- Some people can hold a tremendous amount of fat in their adipose tissue before it backs up and overflows back into their bloodstream. Meanwhile, due to genetics and other factors, other people have a much smaller ultimate capacity in their fat cells before it overflows, and they develop diabetes. This difference in fat storage capacity is known as the Personal Fat Threshold.
The bottom line is that you need to deplete the upstream fuels before your body uses that unwanted fat on your bum and your belly.
Scenario 1 – Modern Processed Diet
To help unpack what this means in practical terms, we have created some diagrams to show you how you can unlock each of these fuel tanks and burn your body fat. Given alcohol, ketone and protein are not significant fuel sources for most people we only need to focus on are glucose and fat.
The body has four main storage compartments for energy – blood glucose, liver/muscle glycogen, fatty acids in the blood and body fat. These storage containers are separate but interconnected to a degree.
You can think of the energy flowing downhill from left to right (i.e. based on oxidative priority). If one of the downstream storage containers becomes overfull, the energy can flow back upstream due to excess pressure in the other fuel tanks.
This first image shows glucose in your blood, glucose in your liver and muscles (glycogen), fat in your blood and fat in your liver as four separate “fuel tanks” all connected by a “pipe”. You’ll notice that the pipe connecting each of the fuel tanks flows downstream towards the right. You should also note that the pipe is not drawn the pipe at the bottom of each tank. You don’t need to exhast or empty each tank for the downstream fuels to be used, but rather deplete to normal healthy levels.
In the modern processed diet, all of these fuel tanks are full. All the upstream fuel sources are “backed up”, so you never need to call on your body fat for energy. When we eat low nutrient density, hyper-palatable foods, we continually fill our fat and glucose stores at the same time.
It’s easy to overeat these highly processed, hyper-palatable foods. We have no off switch for them when they are available, so all storage tanks become overfull. This leads to energy toxicity, metabolic syndrome, diabetes, etc.
Scenario 2 – Low Carb/High Fat Diet
The good news is that, when we reduce carbohydrates using a low carb or keto diet, we can start to drain our glucose stores.
However, even if you are not eating carbs, your body can always refill your blood sugar from the glycogen stores in your liver. This is why your blood sugars can continue to rise even when you haven’t eaten anything.
Also, if the downstream fuel tanks are backed up, you will still see high blood sugars. The blood sugar, liver glycogen and fatty acids in your blood will never go to zero because they can be topped up from the downstream storage tanks (via gluconeogenesis). This is why people with more body fat tend to have higher waking blood sugars.
Because your blood glucose is a small fuel tank (i.e. about 5 g of glucose or 20 calories worth), it fills and empties quickly before and after meals. It’s also very easy to measure using a glucometer to get a precise understanding of your current energy status. When we measure glucose, we are getting an accurate understanding of whether all the downstream fuel tanks are also overfilled.
In Data-Driven Fasting, we simply measure blood glucose before meals. Data-Driven Fasting guides people to drain their glucose stores by waiting until their blood sugar drops below their personal blood sugar trigger point.
Waiting until blood glucose has fallen below their personal trigger stops people from overfilling their upstream fuel tanks. This, in turn, causes your body to call on the liver and muscle glycogen to refill the blood glucose and guides people to deplete their fatty acids in their blood, which can be refilled from their body fat, and voila, fat loss from the body!
However, where some people run into trouble is when they refeed with a very high-fat diet (which tends to have low satiety, so we end up eating more of those foods). High-fat foods tend to provide a lower satiety value, meaning that we tend to consume more calories when our diet has a higher percentage of energy from fat.
Because the fat fuel tank in our blood is always topped up from dietary fat, there is never an opportunity for body fat to flow back into the bloodstream to be used.
We have seen this in a number of people using Data-Driven Fasting who have very low and stable blood sugars but are still carrying a lot of body fat. Due to a mistaken belief that fat is a “free fuel” because it doesn’t raise insulin over the short term, it appears that they are continually refilling their fat tank even through their blood sugars look amazing!
When people get stuck at this point, we recommend they focus on increasing the percentage of protein in their diet (i.e. by reducing both dietary carbs and fat). This tends to improve satiety and allow both the glucose and fat fuel tanks to be drained. We’ll discuss this more in Scenario 4, but first, let’s touch on the low fat/high carb scenario.
Scenario 3 – Low Fat/High Carb
In the high carb/low-fat scenario, even though someone is continually filling their blood glucose and glycogen stores, so long as they are not eating a significant amount of fat, their blood fats will be depleted. Hence, stored body fat will flow back into the bloodstream to be used for fuel.
While a very low-fat diet can be useful for weight loss, the reality is that very few people (unless they adhere to an ultra-strict whole food plant-based diet) can sustain a diet with low enough fat to drive fat loss over the long term. As shown in this chart from our satiety analysis, very few people manage to maintain a very high carb diet, but rather gravitate back to foods that are a mixture of carbs and fat, which allow us to consume more calories as we fill all fuel tanks at the same time.
The majority of our modern processed, packaged foods are a combination of starch, sugar and fat from vegetable oil that makes refined fat hard to escape for most people.
Scenario 4 – Adequate protein/Lower carb/Lower fat
In this final scenario, we have a diet that is lower in fat and carbohydrates with adequate protein and a higher nutrient density. When we eat, we need to get adequate protein and nutrients. You can think of carbs and fat as fuel, and we don’t need as much of it if we are already carrying a lot of unwanted body fat on our body and a build-up of glucose in our liver and blood.
Once we dial back both dietary fat and dietary carbs, we deplete the carb and fat fuel tanks in our body, and our body fat can flow back into the bloodstream to be used.
Foods with a higher protein percentage and higher nutrient density tend to be very hard to overeat. So, in time, the body fat has an opportunity to flow back into our bloodstream from storage.
While you don’t have to jump to a super high protein extreme, ratcheting back easily accessible energy from both carbs and fat (while still getting adequate protein and nutrients) is THE SECRET to ensuring fat loss from your body.
As shown in the chart below from our satiety analysis of data from Optimisers, the average protein intake (i.e. around 15% of calories) tends to align with the lowest satiety outcome and greatest energy intake. If we can progressively increase the percentage of protein in the diet (by reducing energy from both carbs and fat), we will tend to consume fewer calories as we drain our carb and fat fuel tanks.
We’ve been stunned by how well people have taken to Data-Driven Fasting. It seems most people would prefer to test their blood sugars a couple of times a day than attempting to micromanage calories in vs calories out. Measuring your blood sugar gives you an instantaneous measure of your current energy status and enables you to solve the energy balance equation.
Data-Driven Fasting is a great way to get started in your journey towards optimising your health. If you want to identify your Personalised Trigger, you can download the free baselining spreadsheet here or the 130-page manual here to learn all about Data Driven-Fasting.
Check your macros
If you find your blood sugars are great, but your fat loss has slowed, it might be worth checking your current macro intake to ensure you are getting enough protein and not too much dietary fat, so you are not overfilling your fuel tanks. You can use our free macro calculator to find your target macros.
Free Food Discovery Challenge
If you want to take things to the next levels and fine-tune your nutrient density by adding in foods and meals that contain more of the nutrients you aren’t getting enough of, you can take our Free 7 Day Food Discovery Challenge here.