In Part 1, we established that eating less than about 50 grams of carbs per day puts you squarely in the hardcore keto group.
Your liver can actually store about 3 times that amount of glycogen though – about 150 grams.
Therefore, eating less than that per day means that you will use up your liver glycogen quite quickly (especially if you exercise) and then switch to fat burning.
This sort of “low-carb” dieting won’t get you into full blown ketosis all of the time, but if you decide to fast for a little bit, cut even further on carbs, or exercise, then you are going to trigger the process more easily.
In fact “low-carb” doesn’t really have defined parameters. You could say that anything below the average carbohydrate consumption, which is about 300 grams/day in the US, is low-carb.
Why Go Keto?
There are several levels of keto mentality, ranging from the pragmatic to the pseudo-religious.
Here they are in ascending order of nut-jobbery:
- Ketogenic dieting helps me adhere to a calorie deficit because fat is more filling and I find it difficult to overeat.
I feel less sluggish on the keto diet and I don’t experience sugar crashes anymore.
- Keto burns more fat than a regular carb-inclusive diet because it doesn’t need to work through glycogen stores first.
- You have lots more energy when you’re in ketosis and you’re always burning fat so you lose weight so much quicker.
- Ketones are a cleaner energy source than carbohydrate, they have a muscle sparing effect, can cure diabetes and prevent cancer.
- Ketogenic dieting triggers your immortality genes and extends your lifespan by years. It’s entirely possible that you will never die.
The only one that makes absolute sense here is the #1 on the list.
Some people find that they can lose weight/body fat more successfully on a ketogenic diet because they feel fuller and can therefore stick to a calorie deficit with greater ease.
So, that’s the answer to the question: Diet adherence is the most solid reason to follow a ketogenic diet.
Number 2 on the list is possible as well in the right circumstances, particularly if the individual is going from an uncontrolled, high-carb diet to a ketogenic one.
Number 3 is partially correct in that ketogenic diets do result in a higher rate of fat burning.
However – and this is a big HOWEVER – of course you’re burning more fat at greater rates in ketosis – because you are eating more fat.
Alert!! Alert!! – if some keto zealot is telling you that you’re only burning fat in ketosis, it shouldn’t be news to you. What they are neglecting to remind you of is that it’s absolutely necessary, because you’re consuming so much more of it.
And there’s nothing simpler for the body than storing fat as fat, just so there’s no misunderstanding. A calorie deficit is still necessary in order to lose weight because any surplus of fat will be stored just as easily as putting a shirt on.
Number 4 is an extension of this and goes a bit further to say you have more energy!
It’s where I have to really draw the line with people. At least Number 3 has some kind of logic, even though they are missing the point by a mile.
The Energy Debate
More energy on keto. This concept comes from people who have interpreted from certain studies and scientific literature that fat can yield more Adenosine Triphosphate (ATP) than glucose.
The real cuckoos go on to say that glucose is an inefficient form of fuel/energy and that the body “prefers” to burn fat because it’s so much more dense with energy.
First off, if our bodies “preferred” to burn fat then surely it would prioritize fat as the primary source of fuel, and not glucose which in fact it does?
Secondly, the fact that fat can yield more ATP when compared unit for unit with carbohydrates doesn’t make it automatically more efficient.
Per given volume of oxygen, glucose yields more ATP than fat.
The oxygen cost of burning fat doesn’t hinder us much when we’re going about daily business, but if we’re glycogen-depleted when we come to do exercise, it can make a whole lot of difference.
Low Carb versus Ketogenic
Considering the hardcore keto-pushers talk about how much energy is flowing through them all the time, you’d think it would translate to higher energy for exercise, and thus greater muscle and fitness gains.
Despite what they say, we’ve known since 1920 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1263890/] that for a given volume of oxygen, more ATP can be generated from carbohydrate compared to fat.
As exercise intensity increases, oxygen becomes the limiting factor and so our bodies rely more and more on carbohydrate – and therefore glycogen – to get the job done.
Now, we can train our bodies to become more efficient with respect to oxygen utilization by exercising at certain percentages of VO2 Max.
Keto advocates often think this means that we can somehow convert our bodies to perform at maximum potential using fat as the fuel.
In fact what we are doing when we train is adapting our bodies to be more efficient with our use of oxygen.
This means that if you took two endurance athletes – 1 on a ketogenic diet, and 1 on a regular carb-inclusive diet – and trained them, they would both improve their VO2 Max, which is a measure of the capacity for oxygen consumption.
However, the ketogenic athlete would still not be able to perform at the intensity of the carb-inclusive athlete because the latter still has that greater ATP production from glycogen.
Like I said, the issue is pretty much moot in the context of most of everyday life, but competing athletes, or people who want the best results from their training, may want to think long and hard before going full keto.
If you want to delve into an elegant study that demonstrates the limitations of low-carb diets and athletic performance then take a look this one from 2016.
And if you’d rather read a lovely interpretation of that study together with some expert insights from it, then you’d be hard pressed to find a better example than the one by Kamal Patel and the Examine team
That study involved race-walkers, a third of whom followed a ketogenic diet and the other two thirds a regular carbohydrate-inclusive and high carb diet.
Both groups improved their aerobic capacity, and the keto group improved fat-oxidation rates. However, the increased fat oxidation increased oxygen cost, thereby reducing performance at race pace.
No improvement in a 10km test race occurred with the ketogenic group.
Conversely, the moderate-carb and high-carb groups improved their efficiency of oxygen consumption and beat their previous race times by 5.3% and 6.6% respectively.
It stands to reason that the keto group’s fat oxidation rates would increase given their dependancy on fat as their fuel source. As I mentioned before, it is known that more ATP can be generated from carbs per volume of oxygen when compared with fat.
Therefore it also makes sense that with increased fat oxidation comes increased oxygen demand, a limiting factor in exercise performance.
Again, none of this matters until you are approaching maximal output and require your anaerobic engine to contribute some energy.
Compromises – Intermittent Fasting and Keto Windows
Of course, not all keto advocates buy into the nonsense that pervades the internet.
While many zealots vilify carbohydrates, the smarter ones understand the importance of glycogen and at least some consumption of carbohydrate is accounted for by them.
With that in mind, there are several options for someone looking to get the benefits of a keto diet, the chief of which is to more easily adhere to a calorie restriction, together with the benefits of carbohydrate feeding for optimal physical performance.
Again they have abbreviations, but it doesn’t really matter what you call them as long as you get the concepts.
Any method which cuts a compromise falls within the general category of intermittent fasting, or IF.
IF is exactly what it sounds like: fasting intermittently. There are many ways and schedules by which to run it by. Some people go a whole day or two without eating and then eat normally for a few days.
Others have feeding windows and fasting windows within a day. It’s all about finding the right fit for you, while keeping in mind that the objective is to encourage an overall calorie deficit.
Athletes and those looking to tinker with their body composition might try methods such as CKD – Cyclical Ketogenic Dieting or TKD – Targeted Ketogenic Dieting.
The cyclical approach – CKD – is more like intermittent fasting but only with carbohydrates. I’ve seen it called Intermittent Carbohydrate Restriction.
The idea of course is to follow a ketogenic diet for a period of time and then “re-feed” with carbohydrates at given junctures.
Nascent research into this sort of practice has highlighted the possibility that flicking the ketosis switch regularly might help certain endurance athletes accelerate their transition into, or improve their efficiency of, fat oxidation.
More research is definitely needed. Also, it would take some getting used to the the process of triggering ketosis and then kicking back out of it with carb ingestion.
Personally, I believe the adjustment period into ketosis can be too long for some people to consider doing this on a weekly basis.
For the athlete, however, getting into the true metabolic state of ketosis is probably not the most important thing.
The focus is more likely on switching between glycolysis (conversion of glucose to pyruvate) to lipolysis and beta-oxidation (the breakdown and oxidation of fat) for ATP/energy generation via different pathways.
Targeted Ketogenic Dieting is even more specific than CKD because the carbohydrate feeding is done around workouts, and can be tailored for exercise intensity level and competition.
The general idea is to fuel with carbohydrates before, during and immediately after a workout, and follow a ketogenic lifestyle at all other times.
For me, this makes the most sense, if you want the best of both worlds. With this targeted approach you will be restocking liver glycogen and possibly some muscle glycogen, both of which are useful for energy provision and post-workout recovery.
All while being able to stay really low-carb.
Seasonal athletes sometimes follow a ketogenic diet in their off-season so they are not compromising intensity during their competing season.
Summary of Points on Ketogenic Dieting
- The body uses a mixture of carbohydrate and fat as fuel by default
- Despite what many people think, glucose yields more energy than fat per volume of oxygen
- In carbohydrate depletion however, the body must rely more on fat for energy
- At a certain point of fat traffic through the liver, carb depletion and insulin inactivity (in some circumstances), ketones are produced by the liver
- Ketones are essentially packets of fuel which can travel to cells, organs and tissues that fat cannot
- Ketones are converted back to Acetyl-CoA in cells’ mitochondria, which is used in the citric acid cycle/Krebs cycle to generate ATP
- Glucose and fat also yield Acetyl-CoA during aerobic glycolysis and beta-oxidation respectively
- The liver itself cannot use ketones and needs glucose to store as liver glycogen. Red blood cells, certain parts of the brain and the kidneys also need glucose to function.
- In the absence of carbs, the process of gluconeogenesis generates glucose from non-carb sources such as glycerol and protein
- Gluconeogenesis is highly regulated and will not result in excess glucose production beyond that which is needed, even where excess protein is consumed. Hence it will not “kick” the body out of ketosis automatically
- It has been shown that progress in athletic performance will be impaired if the athlete is in a state of nutritional ketosis
- This applies to endurance athletes who are attempting to improve “fat adaptation” by following a chronic ketogenic diet
- Diets providing regular or periodized carbohydrate availability do not impair athletic performance and progress
- We can apply this to resistance training and other high-intensity training, perhaps even more so considering the reliance on the anaerobic system
- It may be difficult for ketogenic dieters to add lean body mass from resistance training due the appetite suppressive effects of the high-fat diet preventing them from attaining a calorie surplus.
- Even in calorie surplus, a ketogenic dieter may not be able to exert as much power given their lack of immediately available anaerobic fuel source; glucose, and muscle glycogen (stored glucose).
Click here to read the final instalment of this Keto article