Dietary calories from conventional diet: (Carbohydrates: Protein: Fat) ≈ (50% : 15 %: 35%)
Dietary calories from ketogenic diet: (Carbohydrates: Protein: Fat) ≈ (5% : 20% : 75%)
Principle: The ketogenic diet causes the human body to mistakenly believe it is in starvation mode, insulin is lowered, glycogen is depleted, the liver converts fat into ketone bodies, the brain begins to adapt to ketone bodies, and the body's primary 'fuel' changes from glucose to fat.
The process of ketogenic diet:
Stage 1: Before starvation: there is enough glucose in your body, on a regular diet (high carb), due to the presence of Uncle Insulin, your body 'loves' glucose the most, and must prioritize its use as 'fuel' under normal circumstances.
Stage 2: Starve for a while: your body runs out of glucose, once your body is starving and your blood sugar drops, Uncle Insulin is content to go to rest, and Big Mama Glucagon takes the opportunity to start making glucose out of all kinds of other non-carbohydrate raw materials (the scientific name for this process: gluconeogenesis).
Quote from Wikipedia: Glycolysis, also known as gluconeogenesis, refers to the process by which non-carbohydrates (lactic acid, pyruvic acid, glycerol, sugar-producing amino acids, etc.) are converted to glucose or glycogen.
Gluconeogenesis occurs mainly in the liver, and students can imagine that the liver is the little factory of gluconeogenesis, and the big glucagon mom is the supervisor of the factory. So what are the main raw materials used to make glucose in the liver's little factory at this stage:
1. Glycogen in the liver (mentioned above, similar to the buffering in the video)
2. Amino acids converted to glucose via transamination
3. Glycerol (mentioned above, the 'backbone' broken down from fat)
4. Oxaloacetate -Not mentioned before, it used to be involved in the tricarboxylic acid cycle in the liver, but now due to the extreme shortage of glucose in the body, oxaloacetic acid has to be 'sacrificed' to be converted into glucose (please remember this name in your classmates!!!! Oxaloacetic acid!!! It will be mentioned again below)
The second stage is summarized in one sentence: when you have been starving for some time, your body does not have enough stored glucose, and starts synthesizing glucose from other non-sugar substances to try to make up for it.
Stage 3: Feeling Emptied @. @
By this stage, most of the substances (glycogen, amino acids, oxaloacetate, etc.) that your body can use for gluconeogenesis (synthesizing glucose) are gradually running out. However, your brain is used to "eating" a lot of glucose every day for energy! So your brain feels "emptied" and begins to scream, "I need more energy! During this period, symptoms such as headaches and fatigue can occur, which is often referred to as the ketogenic adaptation period. As bad as things may seem, your body isn't that stupid! At this point, your clever body will start looking for new alternative fuels on its own - it suddenly remembers that "Hey, you still have a thick layer of fat under your skin (especially on your stomach) to burn! It can't be converted into glucose, but it's still fuel, so let's find a way to utilize it!
So, at the urging of your glucagon mom, your fat cells reluctantly contribute fat and transport it to your liver. But as we just said, there's no way to turn fat into glucose! So what does the liver do with all that fat?
Stage 4: The keto baby is born!
Here's the liver's "original plan" for how to utilize the fat: First, fatty acids are oxidized by β-oxidation to synthesize acetyl coenzyme A, which then enters the tricarboxylic acid cycle and produces the energy molecule ATP, which is transported throughout the body for use as an energy source. (The right part of the picture below.) This process of the tricarboxylic acid cycle requires the involvement of oxaloacetate.
The ideal is very rich, the reality is very bony ...... plan can not catch up with the change. I don't know if you remember the "oxaloacetate" mentioned above! The "stupid" liver didn't realize that in the second stage just described, oxaloacetic acid, the key guy, had already been broken down into glucose! Without oxaloacetate, the tricarboxylic acid cycle is blocked, and a large amount of acetyl coenzyme A accumulates in the liver, doing nothing! The liver has no choice but to convert the large amount of acetyl coenzyme A produced into ketone bodies as the concentration of acetyl coenzyme A rises.
Since ketone bodies cannot be absorbed and utilized by the liver (liver mitochondria lack oxaloacetate), they enter the circulation, are transported to other cells in various parts of the body to be absorbed and utilized, and then re-synthesize coenzyme A, finally entering the tricarboxylic acid cycle as desired to produce ATP energy molecules ...... (as seen in the left portion of the image above).
Stage 5: 'Gasoline car' becomes 'diesel car'
OK, so now there are ketone bodies, then what? Here is a brief introduction to the brain and muscle "fuel" changes: brain "fuel":
1. Priority to eat glucose (the body's normal state, the brain baby favorite glucose)
2. Make do with ketone bodies (only in the body's starvation state, the glucose level is low, the brain baby will be naturally switched to "eat" ketone bodies, and also "eat" very Happy! Because ketone bodies produce more energy and are more efficient than glucose as fuel)
3. Can't eat fat (because lipoproteins are too big to cross the brain's cell membranes, so the brain can't "eat" fat at all)
Muscle "fuels":
1. Can eat glucose (or myoglycogen)
2. Can eat ketone bodies (when the body just When the body starts to starve, the muscles mainly rely on ketone bodies for energy)
3. You can also eat fat (once the body has been starving for a long time, the muscles that know how to do something will "let out" the ketone bodies for the brain to "eat", and slowly get used to "eating" fatty acids themselves. In this way, the body's blood ketone concentration can rise, and the brain can get enough ketone bodies).
On a ketogenic diet, this process, which we often refer to as adaptation, usually lasts 4-8 weeks. After the adaptation period, the body's fuel is completely changed, just like a gasoline engine becomes a diesel engine. In the past, the body mainly relied on "burning" carbohydrates for energy, but now it has become "burning" fat for energy.
Trivia: Does the ketogenic diet cause muscle depletion?
Some students may ask: "What about the fact that in the absence of carbohydrates, the body will replenish the glucose it needs by breaking down amino acids (from protein). Wouldn't that break down my muscle tissue? I want to "lose fat" but I don't want to "lose muscle"!"
A: In the fifth stage described above, when the brain learns to "eat" ketone bodies and the muscles start to "eat" fat, the body no longer needs as much glucose. In this way, gluconeogenesis is greatly reduced. So the body no longer needs to break down proteins to produce glucose, which is why adapting to a ketogenic diet doesn't lead to muscle loss.
The five phases described above are the metabolic changes that occur when the body is extremely starved or on a hunger strike. The ketogenic diet mimics the physiological changes of a hunger strike by relying on an extremely low carbohydrate profile. At the same time, because of the high fat intake, it keeps your stomach full without suffering from hunger pains.