Does need for energy or the presence of fat drive ketosis?

(Ryan Tuttle) #1

Does the presence of fat in the blood stream cause the liver to convert to ketones? Or does the body start converting fat to ketones out of metabolic need?

Im wondering this because if the conversion is driven out of metabolic energy needs then why are there extra ketones that are being excreted in the urine and breath? And on the other hand if the body converts fats just because they are present then wouldnt it be difficult for someone to retain dietary fat as body fat?

Or am i totally off base with these questions? Lol

(Erin Macfarland ) #2

Following!

(Eric Bryant) #3

Great Question! Following as well.

(Deb) #4

Excellent question! Following also

(Jim Russell) #5

I don’t have a reference, but I believe that it is an absence of energy combined with low insulin. I am currently fasting and have not eaten any fat for 36 hours, but I have ketones in my blood. If it was presence of fat in the blood that caused ketosis, you would not be in ketosis while fasting. On the other hand, if it was merely the presence of fat in the blood that caused ketosis, you’d be in ketosis whenever you ate a very fatty meal regardless of how many carbs you ate or what your insulin level was.

(Ryan Tuttle) #6

All good points. Its obviously complicated.

#7

Ketones are an evolutionary adaptation to fuel giant human brains so lack of glucose energy for the brain drives ketosis. Not enough glucose, brain can’t use fatty acids, ketones need to be produced to fuel the noggin.

(Doug) #8

I agree, Jim. Too much insulin, and we know the usage of fat for fuel is greatly diminished, as the body is in the mode of storing it away, rather than bringing it out of storage. The “need for energy” is real, and the body is not going to shut off the heart, lungs, liver and kidneys, among other things. When somebody is insulin resistant/hyperinsulinemic and not fat-adapted, and there are not enough sugar molecules in the blood, liver, or muscles to draw on, then no wonder the metabolism may be slowed down - the body is taking care of the real essentials to maintain life, first, and some other things, like heat for extremities, might get shorted.

The presence of of fat is one thing; it’s the burning of fat for fuel that causes ketosis.

(Todd Allen) #9

We always have fat, aka lipids, in our blood. The standard blood test called a lipid panel measures some of them, such as triglycerides and the lipoproteins/cholesterol. One can have very high or low levels of one or more blood lipids regardless of whether one is producing ketones or not.

When there has been insufficient carbohydrate intake to meet the body’s needs for glucose, the liver releases stored glycogen to sustain the fasting blood glucose level. As glycogen is depleted the liver produces ketones from fatty acids and glucose from protein and a little from fat. Some tissues like muscle will transition from burning glucose to ketones to fatty acids sparing glucose and ketones for where they are essential like red blood cells and the brain.

Some dietary fats like MCTs are more readily converted to ketones and can boost ketone levels.

(Sjur Gjøstein Karevoll) #10

The process and regulation is actually explained pretty well on the Wikipedia page https://en.wikipedia.org/wiki/Ketogenesis

To give the brief-ish summary, let’s go about it backwards. Ketones are produced when there’s a high concentration of acetyl-coa in the liver. Acetyl-coa is used to produce atp in the Krebs cycle, so high concentrations happen when the Krebs cycle is slowed down or the production of acetyl-coa is increased.

Production of acetyl-coa is increased when you consume metabolites that can only be metabolized in the liver, like mcts or deaminated amino acid (like leucine). So there’s one way to get ketogenesis rolling.

The Krebs cycle is slowed down when an important intermediary, like oxaloacetate, is depleted. Gluconeogenesis does just that, so in the end you could say that ketogenesis is caused by gluconeogenesis. If you want to go even further, gluconeogenesis happens on its own, but is inhibited by high levels of insulin or glycogen stores and further increased by glucagon (which is pretty much just anti-insulin (and no, that doesn’t automatically make high glucagon a good thing, especially if you struggle with high blood glucose levels)).

Lots of details missing, and lots of other interactions happening; the body is an amazing Rube Goldberg machine, but this is the gist of it, and if you want more detail you could do worse than Wikipedia.

(Sjur Gjøstein Karevoll) #11

As for why you excrete ketones, that’s part of the compensatory mechanisms that regulate homeostasis, and especially blood pH. Because ketones are acidic and will eventually sour your blood too much you need to keep them in check.

Too high levels of ketones will cause insulin to increase and stop gluconeogenesis, but the body doesn’t really want to do that unless it’s absolutely necessary because if you are producing glucose you presumably need that glucose, and there are other ways of dealing with excess ketones before resorting to that measure.

The first is excretion through urine, and during moderate nutritional ketosis you’ll find some amount being excreted through your kidneys.

As ketone levels increase you will activate an enzyme called acetoacetate decarboxylase which aids in the breakdown of acetoacetate to acetone (a process that happens spontaneously but at a much slower rate). This process in itself decreases acidity because it requires hydrogen ions.

Acetone is pretty volatile and will readily escape the body through any mucous membrane when it’s found in high concentrations. Particularly it will escape through breath due to the high exchange rate.

As you become more keto adapted your ketone levels will drop to some degree. If this is because your glucose demands decrease, you become better at metabolizing ketones (so there’s less excess) or a combination of both I don’t know and would be interested in figuring out. It could also be people tend to become less strict with their diet than before and aren’t as concerned as they used to be eating that half bell pepper or whatever it is that’s going to slightly nudge their ketone levels lower.