Glucose vs Fat

Before I start, just massive thanks to Dr. Ted Naiman for letting me use some of his charts. His charts are quite easy to read and I learn a lot by following him and many other low carb advocates.

Explaining how our body works is quite difficult for me. Especially since I am not medically trained. At the same time, it is a fascinating subject, now that it caught my curiosity in relation to ketosis.
This is to say that if I start rambling do let me know. It's easier to get side tracked when all is linked.
Anywan, I will try to explain in the most simplest of terms the relation between glucose and fat in terms of storage and use for energy.

Our bodies are designed to work on fat.
Think about it!
You have a small, quick accessible storage for glucose in the form of glycogen mainly in the liver but also muscles. By the way they are three parts water which is why when you start keto, and you deplete your glycogen reserves, you lose quite a fair bit in one go. We call it the water weight.
The rest of the body is for fat storage.
I like to see glucose as nitrous and fat as plain fuel in one of those drag cars. So you will drive nicely with the plain fuel but if you need a boost you press the nitrous button for more power.

On a normal diet, we get our energy from both glucose and fat. Fat will travel in our blood stream in form of triglycerides. As fat is hydrophobic, not water soluble, it has to travel inside low dense lipoproteins, together with cholesterol, non soluble vitamins and other micronutrients. Glucose is soluble so it's dumped straight into blood stream.
Our storage for fat and glycogen are replenish throughout the day but as we have a limit capacity for glucose storage, glycogen, and our body can't have too much glucose floating around the metabolism switches to burning glucose.
For this insulin is pumped into the blood to lower glucose by forcing cells to use it for fuel. While this happens, fat is kept in lockdown.
And if glucose is still too much it will be turned into fat via process of lipogenesis.

What happens to the fat we eat? Well, we burn glucose because we have too much of it not because it's the preferred option. Or perhaps it's the preferred option because it has be used to prevent other complications.
And since glucose has to go first, our fat sits tight, doing other stuff, until glucose is no longer present. For this to happen you can't eat carby meals every 3 hours. Eventually all the remaining fat will be directed into storage, waiting to be allowed out again.

So in sum when we eat carbs:
  • Glucose is present in the blood
  • Insulin comes out
  • Fat is lock down
  • Not enough space to store any leftover glucose
  • Glucose will be turned into fat to be stored elsewhere
  • Fat will be stored
When we don't eat or don't eat carbs:
  • Glucose stays low
  • Insulin is not required or in small doses
  • Lack of insulin tells cells that fat can be used
  • Body runs on fat
The body is capable to run on fat. Both the dietary fat, the fat you eat and the body fat, the fat stored.
This mostly takes form of triglycerides as it travels through your body which is  basically 3 fatty acids linked by glycerol.
And glycerol is in fact sugar as it can be turned into glucose by the process of gluconeogenesis. And this process allows the body to create any glucose it needs.

I'm going to stop here as I feel this subject can go indefinitely.
Just one thing though: always choose good quality fats. See the fat section in the food list.