Have you ever wondered if you are a fat burner or sugar burner? Understanding how the metabolism of a sugar burner vs fat burner works can affect your fitness goals.
The human body is a super cool thing. It’s hard to imagine a body more suited to existence on this planet than ours. We have been able to survive droughts, floods, famines, and wars, but something is making us all super fat and killing us slowly.
One of the mechanisms that we have developed to survive changing situations is the ability to metabolize either sugar or fat for our daily energy needs. This is an evolutionary advantage, as stress hormones cause an increase in blood sugar that can be used as a source of fuel to either fight or flee.
But how is this ability to burn sugar making us fat?
A Biology Lesson
At the risk of getting overly complicated, I want to give you an idea of how we use “calories” and what kind of energy we get from them. All our food, protein, carbs, and fats are made of atoms, with the “energy” being stored in the bonds between atoms.
These molecules are mostly made of Carbon, Hydrogen, and Oxygen, and it is the breaking of a bond between two atoms that releases energy.
We need a way to capture that energy efficiently, to be used in very small increments, and to be available all around the body, not just where the food is. To do this, we use the breakdown of our food to make a molecule called Adenosine Triphosphate (ATP).
Molecular Currency: But You Can’t Just Print All You Want…
ATP is called “the molecular currency of the cell,” because it is a coenzyme in just about every chemical reaction that requires the input of energy. In any anabolic (building up) processes, ATP inputs the energy to create the new chemical bonds.
Think of chemical reactions in our bodies as using a gift card, that once used, is all used up, regardless of the transaction amount. So if you “buy” something for 4 Kcal/mol (a silly scientific unit of energy) and you use a 7 Kcal/mol (same silly unity of energy) gift card, you’ve “wasted” 3 Kcal/mol.
This is why we can’t just break up sugar and fats willy nilly in our bodies. Since the “wasted” energy is not really wasted but given off as heat, if we used glucose as the source of energy for normal chemical reactions, the leftover energy would burn us up.
These sugars and fats need to be systematically broken down such that we can capture the energy released in our much smaller “gift card” units, ATP.
What Is A Sugar Burner Vs Fat Burner?
Our ATP is constantly being created and used up, storing energy from our food, then releasing it to be used to build new muscles or other structures. If you could capture every molecule of ATP made by our bodies in a day, you’d have your own weight in ATP by the end of the day. Wild stuff, huh?
I say all this to say that there are two main ways our bodies get ATP.
- By Burning Fat
- By Burning Sugar
If you burn one molecule of glucose (6 carbon atoms), you can, theoretically, obtain 38 ATP molecules. On the other hand, if you burn an 18 carbon fatty acid, you would expect 3 times as many ATP, but in reality you get much more than that. You can get up to 148 ATP.
Nothing good comes from removing the fat.
For this reason, free fatty acids are a far superior fuel source to glucose for the large majority of processes in your body (some tissues, like your brain, must have glucose).
Now you get it when they say 4 calories per gram of carbs and 9 calories per gram of fat. And that has been the war cry leading the charge for the “fat makes you fat” folks, pushing the low fat diet that has turned the entire western world into one big fat camp.
How Do You Know You’re In Fat Burning Mode?
Now, what determines whether you will burn fat or store it? If you answered “hormones” you’re a winner! Johnny, tell them what they’ve won!
- A svelte, muscular body
- A lifetime supply of health
- A better night’s sleep
- A stable mood
- A clear head
- A new car! (j/k, I’m not giving you a car)
All these things and more can be yours if the hormones are right. Two of the hormones that determine if you are going to be a sugar burner or a fat burner are insulin and glucagon, among others. Both are necessary for normal functioning, but if they are out of whack, you get what we have in this country…tons of fat, sick people.
Insulin and Glucagon work in opposite ways, and must be kept in a good balance in order to reap the benefits of each, without allowing the harm that can be done by either of them if they get to a high concentration.
Why Is My Body Burning Sugar Instead Of Fat?
The evolutionary advantage of insulin, as a storage hormone, is that it recognizes times of plenty and takes that opportunity to store fat. Insulin is 100% necessary as it keeps blood sugar levels from getting too high, which would be fatal. There are three things that happen to blood sugar when insulin is secreted by the pancreas:
- Some are used as energy – It is important to lower blood sugar so we metabolize it quickly to get our ATP. Since we are getting ATP from sugar, fat metabolism is put on hold until the sugar has been dealt with (which can be many hours). If you continually eat high carbohydrate meals, your body will constantly be in sugar burning mode, storing fat and blocking access to fat stores.
- Some are converted to glycogen – This is a short term storage option for sugar. When people talk about eating carbs before a big race, this is why they are doing it. Glycogen is stored in the liver and in your muscles for quick access to energy (ATP) when blood sugar gets low.
- The rest is stored as fat – Any sugar that is left after the two processes above is turned into triglycerides and transported to adipose tissue to be stored as fat.(1) Fat is a longer term storage form, as it is not readily available to the sugar burner like glycogen is.
Insulin also plays an important role in growth, muscle building, testosterone levels and overall health.
All carbohydrates eaten eventually become individual sugars in your blood stream, some faster than others. Our bodies are very efficient at turning sugar into fat, but not very efficient at turning fat into sugar.
For this reason, if you are in a sugar burning metabolic state, you need a constant influx of new sugars to keep energy up. This is the reason we have hormonal hunger at odd times throughout the day and a constant ebb and flow of energy levels. Ever get the 3 pm crash?
Insulin is both lipogenic and anabolic (so there are some good things about insulin) but for now, we’re going to focus on the lipogenesis, or fat creation, side of the equation.
Does Sugar Stop Fat Burning?
No. When your body generates sugar, it actually encourages fat burning.
Glucagon is, basically, the opposite of Insulin. When your blood sugar gets low, glucagon starts the process of gluconeogenesis (generation of new sugar), to stabilize levels by converting stored glycogen and proteins to blood sugar.
We know that insulin is a fat storage hormone, and glucagon, being the opposite, is a fat burning hormone. It releases fat from its’ storage in cells and allows it to be used to generate ATP to power our normal cellular processes.
The evolutionary advantage here is that you can go a long time without food, and since you have ample stores of fat, your body will have the ATP needed for normal processes and the glucose needed for the few specific functions.
Glucagon is both lipolytic (fat burning) and catabolic, as it breaks down tissues (both fat and protein) to create energy and sugar, respectively.
How long does it take for your body to start burning stored fat?
Your muscles first burn through stored glycogen for energy. “After about 30 to 60 minutes of aerobic exercise, your body starts burning mainly fat,” says Dr. Burguera. [Source]
For less intense exercise, it can take more than 1 hour.
How to Burn Fat First
Of your two options for harnessing energy, your body’s metabolism will adapt to the most available source of energy and become more efficient at turning that energy source into ATP.
If there is more sugar available, from dietary carbohydrates, your body will focus on burning sugar for fuel. If carbs are restricted, or low glycemic carbs are eaten, such that blood sugar never gets too high, and lots of fat is eaten, your body will focus on using and burning fat for its’ fuel.
Dietary fat intake has been shown to have the effect of stimulating fat-mobilizing enzymes called lipases, and inhibiting those enzymes that serve to store fat, such as malic and fatty acid synthase.
It may be counterintuitive, now that we’ve all had “fat makes you fat” beaten into our heads, but high dietary fat intake leads to an increase in fat burning metabolism.
If you take a look at it from an evolutionary perspective, it actually makes perfect sense. Your body will try to conserve that which is in short supply. This is why when you become slightly dehydrated, your body tries to hold on to all the water it has, and when you restrict calories your metabolism downshifts to burn less.
Eat Alot of Good Fat
If you limit your fat intake, your body will recognize this and try not to burn fat, as it may be needed later! If it has a steady stream of available good fat, then there is no reason not to burn it all and more. I say eat a lot of fat, but that comes with a caveat. Eat a lot of Good Fat.
Saturated fat has been vilified by the medical establishment and the media, but their dogmatic defense of the “fat makes you fat” theory is no longer supported by science.
If you have any interest in looking deeper into the how we as a nation got to this point of hating on fat, read Gary Taubes’ discussion, The Soft Science of Dietary Fat. Also interesting is this great article on The 10 Reasons to Eat Saturated Fat that is quick, well written, and well cited (my favorite!).
Fat Burning in Context
For the large majority (99.8%) of our evolution, we have not had access to abundant, highly processed, easily digestible carbohydrates. We have had to hunt and gather our food. It was high in fat and protein and relatively low in carbs, especially processed carbs.
Evolutionarily, those who burn fat are the ones who survive. The peripheral benefits of fat burning metabolism enter into just about every other process in our body.
Since it is an evolutionary advantage to be able to focus on the task at hand, fat consumption inhibits cravings, which serve to severely distract anyone’s focus. It accomplishes this by leading to the secretions of the hormone, Cholecystokinin (CCK) , which:
- Is a neurotransmitter – like Leptin, CCK sends a signal to your brain that you are full. Have you noticed that a high fat/low carb breakfast keeps you satiated well through lunch time?
- Slows food absorption from your stomach – If you have a slower emptying of the contents of your stomach into your blood stream, you’re less likely to get a blood sugar spike, less likely to get an insulin spike, less likely to store fat as a result of the meal, and less likely to be hungry again in an hour.
- Can be naturally enhanced – luckily, simply eating a high fat meal is enough to stimulate the release of CCK and get the beneficial effects. Unlike insulin and leptin, there does not seem to be any evidence that you can become Cholecystokinin resistant, so eat your bacon, eggs, avocados, and prime rib!
What Is The Best Way To Lose Belly Fat?
Some people can eat anything they want, work out or not, and still be ripped, healthy, and in great shape. Others, not so much. I am one of those others that grow belly fat easily. I have to take an active role in my metabolism and make sure that I am doing the right things to encourage fat burning in my body, like:
- Not eating grains, dairy, sugar, and processed carbs
- Eating good fats (Monounsaturated, Omega-3′s, and saturated fat from natural sources like grass-fed beef, organic cheeses and butters, and wild caught fish.)
- Sleeping enough
- Short, intense workouts a few times/week to keep glycogen stores lower
You too can be a fat burner. You can be skinny, or ripped, or fit. If you follow the science, it gets easier and easier. When you’re fighting your hormones and trying to lose fat while in a sugar burning mode, you’re fighting an uphill battle.
Once you get yourself in a fat burning mode, it will take a while to get back to sugar burning mode, so you can afford a cheat meal once a week or so. I suggest you do it. What’s the point of getting fit and healthy if you can never again have the things you love. There’s nothing wrong with indulging from time to time.
Get yourself in a fat burning metabolic state, and the fat will melt off, easily, while you eat till you’re full, exercise when you want to, and still get to “Treat Yo Self.”