MrRippedZilla
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I once got into a "debate" with an individual on another board who was convinced that low protein keto diets are just fine at preventing muscle loss due to the fat intake. I originally put this down as 1 narrow minded idiot but then saw the same mindset occur again & again in real life and across the boards (thankfully, never here). I believe this has a lot to do with the anti-protein trend that I've mentioned before.
So I've decided to dive into some basic biochemistry to explain WHY fat intake alone does NOTHING to prevent muscle loss when dieting. You won't see any references here because this is stuff I learnt at college and can be found in any decent biochemistry textbook (I recommend the one by Berg, Tymoczko & Stryer) so without any further delay let's dive in...
The Krebs cycle, Acetyl groups & Oxaloacetate
In order to burn carbs for energy, you first need to have the acetyl group enter the Krebs cycle (also known as the Citric acid/TCA cycle), which is the main cycle used by your body to produce ATP (your body's main energy source).
Now, in order to get that acetyl group into the cycle you MUST have some Oxaloacetate (OAA) lying around so the two can hook up and form citrate.
Where do you find this OAA stuff?
Well, this is called a "cycle" for a reason. Usually things just go round and round, being re-metabolized (the acetyl group is removed from the OAA) and there is no need for any "new" OAA.
However, OAA has other stuff to do outside of the cycle - one of which is to help produce new amino acids such as Aspartate. In fact, the Krebs cycle has a lot of intermediate steps between the OAA-Citrate hook up that involve a bunch of stuff leaving to make other amino acids (alpha ketoglutarate can leave the Krebs cycle to make glutamate, etc) but I won't go deep into this for fear of losing you folks.
The net result is, no matter who leaves during the intermediary steps, you end up with less OAA and you NEED to find some fresh from elsewhere.
What happens on a normal diet
With plenty of carbs available, OAA comes from Pyruvate (which comes from glucose). Pyruvate is mostly used to generate acetyl groups but some will also generate OAA so those two can hook up and enter the Krebs cycle.
The key point here is that carbs are the main provider of OAA under normal conditions. Fat can be broken down into the acetyl groups via beta-oxidation BUT these acetyl groups NEED OAA in order to enter the Krebs cycle and carbs are doing the supplying.
In fact, you could say that the fat is entering the Krebs cycle and is "burning" while OAA is the "flame" that allows it to enter the cycle. This is where the “fat burns in the flame of carbs” saying comes from; it means that acetyl groups derived from fat can only enter the Krebs cycle to be metabolized for energy if sufficient OAA can be derived from carbs.
Remember, fats can generate acetyl groups but not OAA.
So where does protein fit into this little energy circle?
Just as OAA can produce amino acids, amino acids can enter the Krebs cycle and produce OAA (two-way street) by the same process just reversed. This means the "fat burns in the flame of carbs" saying isn't quite accurate - it's more like "fat burns in the flame of OAA" because both carbs & protein can provide the OAA.
What happens on a traditional keto diet (low carb, decent protein & fat)?
Before going deep into detail here I want to add that OAA doesn’t just leave the Krebs cycle to make amino acids, it also leaves the cycle to make glucose via gluconeogenesis (making glucose, your main energy source, from non-carb sources). Keep that in mind.
So, we don't have enough carbs to supply OAA.
OAA itself is being depleted since some of it is leaving to produce new glucose.
Protein is going to be driven to enter the Krebs cycle but we still have that OAA that is being made leaving for the process of gluconeogenesis so OAA depletion seems inevitable.
Now, what is also happening in the liver (home of gluconeogenesis) is that fatty acids are being taken up, entering the mitochondrion, getting beta-oxidized to acetyl groups and with the end result being a massive oversupply of said acetyl groups.
When you combine this massive oversupply of acetyl groups with the massive under supply/depletion of OAA, you have a recipe for mass accumulation of acetyl groups that CANNOT enter the Krebs cycle because the cycle is operating less effectively and there are too many acetyl groups.
This is the event that causes ketogenesis: oversupply of acetyl groups to a depleted OAA pool where the acetyl groups cannot enter the Krebs cycle. Acetyl groups have nothing else to do except condense with one another to make ketones
Ketones are an energy source so they reduce the burden on the Krebs cycle, which means less depletion of OAA. This works because we still have SOMETHING to make OAA with, namely protein.
So if both carbs & protein can make OAA, and fat can only make the acetyl groups, what happens when you rely on a high fat/low carb/low protein style keto diet?
You lose muscle. It's as simple as that.
You NEED to get that OAA and if isn't coming from diet then it's coming from somewhere within the body. Hmm...I wonder where your body can find a decent supply of amino acids? Oh yea...your gainz. Those muscle gainz are going bye bye. Loss of lean mass is going to be triggered in large part by depletion of OAA, and only carbohydrate/protein together can supply OAA (both of which your stupidly not supplying).
Summary
There you go. A biochemistry lesson, showing what your body does with these energy sources, to justify why low protein keto diets (low protein diets in general actually) are ****ing stupid and there is no justification for it if your goal is to maximize body recomp.
So I've decided to dive into some basic biochemistry to explain WHY fat intake alone does NOTHING to prevent muscle loss when dieting. You won't see any references here because this is stuff I learnt at college and can be found in any decent biochemistry textbook (I recommend the one by Berg, Tymoczko & Stryer) so without any further delay let's dive in...
The Krebs cycle, Acetyl groups & Oxaloacetate
In order to burn carbs for energy, you first need to have the acetyl group enter the Krebs cycle (also known as the Citric acid/TCA cycle), which is the main cycle used by your body to produce ATP (your body's main energy source).
Now, in order to get that acetyl group into the cycle you MUST have some Oxaloacetate (OAA) lying around so the two can hook up and form citrate.
Where do you find this OAA stuff?
Well, this is called a "cycle" for a reason. Usually things just go round and round, being re-metabolized (the acetyl group is removed from the OAA) and there is no need for any "new" OAA.
However, OAA has other stuff to do outside of the cycle - one of which is to help produce new amino acids such as Aspartate. In fact, the Krebs cycle has a lot of intermediate steps between the OAA-Citrate hook up that involve a bunch of stuff leaving to make other amino acids (alpha ketoglutarate can leave the Krebs cycle to make glutamate, etc) but I won't go deep into this for fear of losing you folks.
The net result is, no matter who leaves during the intermediary steps, you end up with less OAA and you NEED to find some fresh from elsewhere.
What happens on a normal diet
With plenty of carbs available, OAA comes from Pyruvate (which comes from glucose). Pyruvate is mostly used to generate acetyl groups but some will also generate OAA so those two can hook up and enter the Krebs cycle.
The key point here is that carbs are the main provider of OAA under normal conditions. Fat can be broken down into the acetyl groups via beta-oxidation BUT these acetyl groups NEED OAA in order to enter the Krebs cycle and carbs are doing the supplying.
In fact, you could say that the fat is entering the Krebs cycle and is "burning" while OAA is the "flame" that allows it to enter the cycle. This is where the “fat burns in the flame of carbs” saying comes from; it means that acetyl groups derived from fat can only enter the Krebs cycle to be metabolized for energy if sufficient OAA can be derived from carbs.
Remember, fats can generate acetyl groups but not OAA.
So where does protein fit into this little energy circle?
Just as OAA can produce amino acids, amino acids can enter the Krebs cycle and produce OAA (two-way street) by the same process just reversed. This means the "fat burns in the flame of carbs" saying isn't quite accurate - it's more like "fat burns in the flame of OAA" because both carbs & protein can provide the OAA.
What happens on a traditional keto diet (low carb, decent protein & fat)?
Before going deep into detail here I want to add that OAA doesn’t just leave the Krebs cycle to make amino acids, it also leaves the cycle to make glucose via gluconeogenesis (making glucose, your main energy source, from non-carb sources). Keep that in mind.
So, we don't have enough carbs to supply OAA.
OAA itself is being depleted since some of it is leaving to produce new glucose.
Protein is going to be driven to enter the Krebs cycle but we still have that OAA that is being made leaving for the process of gluconeogenesis so OAA depletion seems inevitable.
Now, what is also happening in the liver (home of gluconeogenesis) is that fatty acids are being taken up, entering the mitochondrion, getting beta-oxidized to acetyl groups and with the end result being a massive oversupply of said acetyl groups.
When you combine this massive oversupply of acetyl groups with the massive under supply/depletion of OAA, you have a recipe for mass accumulation of acetyl groups that CANNOT enter the Krebs cycle because the cycle is operating less effectively and there are too many acetyl groups.
This is the event that causes ketogenesis: oversupply of acetyl groups to a depleted OAA pool where the acetyl groups cannot enter the Krebs cycle. Acetyl groups have nothing else to do except condense with one another to make ketones
Ketones are an energy source so they reduce the burden on the Krebs cycle, which means less depletion of OAA. This works because we still have SOMETHING to make OAA with, namely protein.
So if both carbs & protein can make OAA, and fat can only make the acetyl groups, what happens when you rely on a high fat/low carb/low protein style keto diet?
You lose muscle. It's as simple as that.
You NEED to get that OAA and if isn't coming from diet then it's coming from somewhere within the body. Hmm...I wonder where your body can find a decent supply of amino acids? Oh yea...your gainz. Those muscle gainz are going bye bye. Loss of lean mass is going to be triggered in large part by depletion of OAA, and only carbohydrate/protein together can supply OAA (both of which your stupidly not supplying).
Summary
There you go. A biochemistry lesson, showing what your body does with these energy sources, to justify why low protein keto diets (low protein diets in general actually) are ****ing stupid and there is no justification for it if your goal is to maximize body recomp.
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