I wasn't aware the body would produce ketones (except briefly overnight) unless under conditions of strictly limited dietary carbohydrate.
Yes, briefly overnight...2 to 6% of energy needs from ketones and then overtime that ketone energy production is increased.
It's perfectly normal to have low levels of ketones circulating. It doesn't mean much, really.
The keto narrative is this: chase the ketones so you'll burn more fat.
As we've already mentioned, some dieters who do the ketogenic diet, don't actually do THE ketogenic diet…the actual thing is really, really difficult…the actual thing is a medical intervention.
Cut to the chase: all calorie deficit diets are keto.
After 3 days of not eating - or on the ketogenic diet - ketone levels are 30-40%.
Yet in a healthy person with a functioning metabolism it is perfectly normal to have ketones that provide a tiny little bit of energy.
In a fasted state, even between meals, you will burn body fat and you may dip into low level ketogenesis and produce ketones BUT it is overall calorie intake that will affect fat loss.
Ketone production is not just about carb restriction but liver glycogen status. And fat loss is all about calorie restriction not ketone production.
It's an important distinction and personally I think this is where all the keto nonsense starts....this belief, this narrative built around the idea that fat burns fat, fat burning beast etc and the polarising of carb v fat as rival gangs in a West Side Story musical mash up of antagonist warring food groups fighting for superiority and gaining an edge for business and profit margins.
Let's move away from this absurdity and be straight....it's total carbon. It doesn't matter, in what form it is in....glucose, lactate, fat, ketone, amino.
What actually is ketogenesis and what is it for?
It is merely a different pathway to exploit energy exchange when food is in short supply. The trigger for it is in liver mitochondria and supported by various hormone signalling strategies.
The reason for this is to provide ketones to fuel the brain as an alternative energy source. The brain requires 20% of daily energy expenditure at rest and is fuelled in a fed state by glucose from dietary sources and from stored glucose in the liver when no dietary sources are available. Other cells containing mitochondria can use ketones too if energy is needed, that is.
Ketogenesis is an adaptation to conserve energy. Why would a process adapted to conserve energy burn more energy, burn more fat?
It doesn't, it just redistributes the carbon so it can be used in a different form with the overall aim of conserving glucose.
Glucose stores are limited, fat stores not so much. Ketogenesis is a way of using fatty acid stores to obtain a molecule that can pass the blood brain barrier to conserve the precious glucose commodity.
You just happen to be burning fat at the time. It is an efficient mechanism to conserve energy with one thing and one thing only as its mission....survival.
There is a dance between insulin and glucagon….one high, one low. When insulin is high, hormone sensitive lipase is disinhibited, when low with glucagon high, HSL is activated. And when it is on, it signals the release of fatty acids from fat stores.
Now….that alone will burn fat.
So the key here is glucagon - HSL. So when you eat, if you keep insulin low, you will get to the promised hormonal land of glucagon - HSL and burn fat right?
Yes. But over a time period if you eat more energy than you need by keeping insulin low you will still store fat and not burn it!!!!
You can be a fat burning beast by literally burning dietary fat and store body fat…..do you see?
So, back to glucagon - HSL. With fat released from fat stores you are now burning it aerobically.
The brain cannot be fuelled by fatty acids, glucose is its preferred source when food is in abundance but ketones can cross the blood brain barrier, to preserve glucose when food is scarce.
Your evolutionary biochemistry is set up for survival. At low levels of ketone production, as mentioned, from an overnight fast being 2-6 % and after 3 days this can be up to between 30-40%. And at the point of higher ketone production the brain uses ketones but it keeps using glucose. So, ketone production is a mechanism that seeks to preserve glucose. It does this for a reason.
Certain neural cells can only use glucose. And cells that have no mitochondria use glucose anaerobically....red blood cells.
So it is with some level of irony that if seeking ketones via a low carb diet, those ketones are protecting the stored glucose which you need for vital biological processes to keep you alive.....you can't fight biology!!
You deny it glucose in the diet, the body makes other molecules to protect the glucose that it has.
And at this point, your body with its sensitive alarms does not know if you will be fed in 4 hours, 16 or 3 months. It is just the start of a structured, organised biological process and as soon as it is started it is over again….the dance between insulin and glucagon begins again when you next eat.
Hence, here, low level ketones.
So the driver isn't really due to low insulin, it is liver glycogen status.
And the driver for fat loss is calorie restriction.
To summarise….ketones do not promote fat loss, they conserve glucose.
That is what ketogenesis does.
There is some complex biochemistry in all this but simplifying it all down…….
In aerobic respiration, the energy molecules in the body are ATP and NADH. To obtain them, carbon in the form of glucose (short chain), fats (long chain) are catabolized…the end product before entering the mitochondria to obtain that energy…acetyl CoA and it enters with a little help from an intermediary, oxaloacetate.
So this is going on, fed or unfed, the fate of carbon…acetyl CoA.
Your body is monitoring blood sugar levels in a tightly controlled range.
Remember here, glucose is feeding the brain which requires a lot of it….if liver glycogen levels start to drop….the keto process starts….
In liver mitochondria, as liver glycogen reduces even nominally, oxaloacetate - the above mentioned intermediary of the citric acid cycle - is diverted to form new glucose - gluconeogenesis - by removing it from mitochondria into the cytoplasm where it is released into the blood to maintain blood glucose levels. (Oxaloacetate is made from pyruvate because of its importance in oxidative phosphoralation can be made from aminos and some ketones too….oxaloacetate is a carbon molecule).
So now, in those liver mitochondria, the oxaloacetate....remember it condensates with acetyl-CoA to enter the citric acid cycle....is no longer available. Now Acetyl-CoA accumulates and with no friend available to escort it begins to breakdown to form ketone bodies. These ketones are sent from the liver into the blood. Cells containing mitochondria can take them up to reconvert them back into Acetyl-CoA. You are in low level ketosis.Think overnight fast. Even between meals perhaps. Post exercise maybe. 2-6% energy use from ketones.
Any metabolic advantage? None....why?
The ketones are converted to acetyl Co-A....the very same molecule that enters the citric acid cycle from glucose and fat metabolism. All you are doing is converting one molecule into another with the aim to burn the carbon it contains, depending on the pathway selected. You have though saved some glucose for your brain.
And all this to protect the vital resource of glucose.
Source of energy substrate catabolised for entry into mitochondria with the final atp output:
glucose: acetyl CoA
fatty acids: acetyl CoA
ketone: acetyl CoA
It's quite majestic!
So IF.
The health benefits of IF is autophagy. The cleaning up of dead metabolites with the result that it makes your metabolism more efficient.
You will be burning body fat, yes. But if you eat more carbon than you need, you will store it too.
The fact that ketones are on the scene does not mean they are causing fat loss....correlation does not imply causation. Fat loss is solely about energy and the Laws of Thermodynamics.
Sorry about that.