Honestly, there is not much in the medical text books about ketosis, since most of it is geared towards ketoacidosis (in diabetics). The biochemistry is similar, but ketoacidosis is a medical concern. My knowledge really comes from jargon-rich biochemistry textbooks.
I’m not an expert because I’m not a dietician or physician, but I do know how the diet works.
Crash course – Our bodies are likely used to a low-carb diet (think cavemen – agriculture is a recent invention in terms of evolutionary time scales)
Let’s think of a typical, 21st century diet. Some fat, some protein, but A LOT of carbs. Breads. Sweets. Sugar. Corn Syrup. None of these things are natural; they’re all man made products. Bacon is natural. Beef, Poultry, Eggs, Vegetables are natural. Fruits? Fruits are cons made by crafty plants – they trick us into eating them.
So you just ate a pie. What happens? Your body senses a rise in blood sugar, meaning you just ate. As a response, your body produces insulin. Insulin let’s glucose into your body’s cells. Insulin, however, is a hormone. It also suppresses your appetite, and enhances « satiation » and inhibits « hunger » enzymes (read: Ghrelin, Leptin, etc). Satiation is that feeling you get after you ate a pie.
But then what? Your glucose levels drop because your cells are using them. Or, maybe insulin isn’t as effective as it used to be, because we eat a lot of pies (insulin resistance). So you might not even be satisfied after that pie, OR, your blood sugar is back down to normal, and you’re hungry again. So, what do you do? Eat more. And because you just « spiked » your blood sugar with a pie, your insulin spiked too, and now it spiked DOWN to « clean up » (sort of like a rebound). This makes you even more hungry.
Now, let’s say you give up the carbs. Your body senses the low blood sugar, and you get hungry. You muscle through it (keto flu). You eat bacon, veggies, and other keto friendly foods instead. Your blood sugar is getting lower. If it gets too low, you’re going to go into a coma and eventually die.
BUT WAIT! You don’t die. Living is generally your body’s number one concern, so it can cope with this low blood sugar. First, it uses glycogen, which is stored in your body (mostly liver). Glycogen is pretty much stored-sugar. This refills your blood sugar to a low, but « normal » level. You’re still hungry, but you’re alive (still keto flu. You SHOULD eat during this, just keto friendly foods. As much as you want. Seriously. Eat a pound of bacon.)
But « glycogen » isn’t unlimited. You run out after 1-3 days. But now what? If your blood sugar goes down, you’ll get tired, sick, etc. But this is when the beauty of Ketosis kicks in. Your body is starting to run out of glycogen, and realizes it. But it has all of this extra fat still. And you know what? That fat can be used for energy too.
Ketosis turns your fat into ketones, which can be used for fuel for almost your whole body. This is euphoric (so keep reading). Your body starts burning fat. Plus, that dietary fat you’ve eaten, helps you burn fat. Your blood sugar goes back up (from ketosis). And let’s face it, you have a few pounds of fat to burn, months, or maybe years worth.
But the thermodynamic LAW says you need to burn more energy than you take in. So this is the euphoric part of the diet. Despite being allowed to eat any keto-friendly food, and as much as you want, you’ll find that you don’t want to. That insulin hormone stabilized – it’s not being « jolted » by all that sugar anymore. Those of us who can not control their hunger are suddenly no longer hungry. I just went 16 hours without eating, and I had to force myself to eat. You also have a lot more energy because of the fat you’re burning. When you’re sleeping, you’re burning fat. When you’re EATING, you’re burning fat. You’re always burning fat.
Your body uses substances like this: Carbs >>>>>>>>>> Fats >< Protein (the >< is there because it depends)
So what does this feel like on a human scale? Day 1 – stop eating 300-500g carbs/day Day 2 – Keto flu (supposedly drinking soup broth works) A lot of people don’t really notice it. You’re burning glycogen at this point) Day 3 – Scale should drop significantly; loss of water weight (you used up all of your glycogen, which holds a lot of water Day 4 – Ketosis kicks in, keto flu lessens or stops. Day 5 – Feeling good, starting to lose appetite Day 14 – Top of the world, maybe lost as much as 15 pounds, and you’re completely satiated
Everyone experiences it differently. I don’t get a keto flu, and I can get into ketosis in a single day.
As I said, the downside of keto is that YOU CAN NOT CHEAT. You can not reward yourself with carbs for not eating carbs. If you make it to Day 5 and eat a doughnut, you can throw yourself out of ketosis. Reward yourself with bacon, or nuts, or something keto-friendly, or don’t reward yourself with food period. You’re not a dog.
Let me know if you have any questions.