- Ketogenic diets are becoming increasingly popular.
A lot of people are talking about them.
You may have been recommended one.
You may already be eating a ketogenic diet.
So in this video, we're going to explain
exactly what a ketogenic diet is,
the potential benefits and disadvantages,
and how it applies to cyclists,
and how you can apply it.
Can you be a competitive cyclist,
and eat a ketogenic diet?
Well, before we go into any of that,
make sure to subscribe to GCN if you haven't already,
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A ketogenic diet, or keto for short,
is a high fat, high protein,
but low carbohydrate diet,
that's designed to put the body
into a state of ketosis, where the body burns fat
rather than carbohydrates for fuel.
Put in a more scientific way,
it's a metabolic state where the body breaks down fat
into fatty acids, and then into ketone bodies.
Ketone bodies are acetone, acetoacetate,
and beta hydroxybutyrate, which are then used as fuel.
Now to achieve it requires very strict discipline,
typically eating less than 50 grammes of carbohydrate a day.
There are many options and permutations to achieve this,
but here is an example of a typical daily diet.
Breakfast could include eggs, bacon,
and perhaps with some wilted spinach or avocado.
Lunch could include a Caesar salad with chicken.
No croutons though, they contain carbs.
For a snack, some nuts such as macadamias.
And for dinner, grilled fish
with some sauteed green vegetables.
The vegetables consumed contain small amounts of carbs,
but this isn't enough to push you out of ketosis.
Foods that you'd avoid on a keto diet,
well, that's pretty much all of the fun stuff.
So bread, pasta, grains like rice and oats,
cookies, croissants, even some fruit,
chocolate, and beer.
And, why uh, little Timmy's birthday cake?
Wait, no birthday cake?
- [Man] Nope.
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- I mean, cutting out little Timmy's birthday cake
seems rather drastic.
Why would you wanna go on a ketogenic diet?
Well, there is undeniably strong evidence
that a ketogenic diet is very effective for weight loss.
Now there are many motives
for cyclists wanting to lose weight.
It might be to improve your power to weight ratio,
for health reasons, or to get leaner for aesthetic reasons.
But it's important to point out
that a ketogenic diet isn't a free licence
to eat as much as you want.
A study in nutrients from 2014 suggested
that the main result of weight loss
from a ketogenic diet still comes
from a caloric deficit.
There are potential health benefits too,
with medical conditions like diabetes.
It's also been shown in some studies
to restrict the growth of particular kinds
of cancerous tumour, Alzheimer's,
and it's long been used as a way
to treat epilepsy in children.
But in many of these cases studies are still ongoing,
and the results are far from conclusive.
Importantly for cyclists, there's a train of thought
that a keto diet can turn you
into a fat adapted athlete,
that's better at burning fat,
and less reliant on carbohydrate as fuel,
turning you into a fat burning machine
with huge energy stores.
Now, this works because humans can typically store
between 1600 and 2200 calories of carbohydrate,
but even very lean individuals still have
over 100,000 calories of fat tucked away.
I know, I mean, hard to believe,
I know, it's true.
I guess that means I'm not allowed
to eat any of this.
Being able to tap into that fat,
and use it as an energy source
by converting it into ketone bodies
would effectively make an athlete bonk-proof,
which is what typically happens
when you're performing exercise
and you run out of carbohydrates,
or blood glucose, and have that feeling
of hitting the wall.
Factor in though, you may see misleading results early on
with a ketogenic diet,
typically two to four kilogrammes
in the first week or so.
Now this isn't muscle or fat loss that you've experienced.
It's usually just water, and the reason for that
is that your glycogen stores have been depleted,
glycogen being how your body stores carbohydrate.
Now to store each molecule of glycogen,
the body also stores three to four molecules of water,
so this loss is just less water in your body.
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Ketosis for athletes is a hot topic right now,
and one that's fiercely contested on both sides.
Now on both sides of the argument,
you'll find people with motives and agendas to push,
and I've tried to be as objective as possible
when going through the scientific literature
that currently exists on the topic.
I don't have an ulterior motive,
or an agenda to push, but to be completely transparent,
I will state that I've never tried
a long-term ketogenic diet myself, yet.
First up, a well cited study
in the Journal of Physiology,
by Burke at al from 2017,
found that low carbohydrate, high fat diets,
impaired exercise economy,
and negated performance benefits
from intensified training in elite race walkers.
Put more simply, the body uses around 20% more oxygen
to liberate energy from fat,
as it does from carbohydrates,
meaning that, well, fat is a less efficient fuel source.
This is offset though by the huge amounts
of fuel that fat provides,
but ultimately the take home message
from this study is that there wasn't an indication
of enhanced performance from this diet.
And further to this, having spoken to coaches
and riders, I can tell you
that no one is competing and racing
in the Tour de France on a ketogenic diet,
and this is because without carbohydrate stores,
or carbohydrate consumed during competition,
you have very little fuel available
for a process called anerobic glycolysis.
This is the body's metabolic shortcut
that rapidly produces energy
by partially burning carbohydrate.
Think of it as your body's natural turbo charger,
and it kicks in and enables you to perform short,
high intensity efforts, such as sprinting, attacking,
or getting up short sharp hills.
Now, to be crystal clear here,
an athlete in ketosis will still have small amounts
of glucose for anerobic glycolysis, the turbo charger.
This is because the liver is capable
of producing small amounts of glucose
through a process called gluconeogenesis.
However, the amount of glucose available
for the turbo charger,
the amount of turbo charger fuel available
will be much, much less
than an athlete who is competing while consuming carbs.
Now I'm gonna go into a little bit of depth,
so brace yourselves, nerd alert,
but it'll help you understand things later on.
Now, ketones can be converted
into something called acetyl coenzyme A,
which is a fuel,
and this is done by an aerobic process,
that means involving oxygen, called beta oxidation,
and this is done by little things called mitochondria,
inside the cells of your body.
However, this isn't as quick as anerobic glycolysis,
the turbo charger.
Burning ketones does have an added benefit
of not producing one molecule of lactate
for every one molecule of ketones burned,
which you do get when you burn sugars.
Now, lactate is associated with that buildup
of, well, lactic acid, burning in your muscles,
but it's not all that bad,
because lactate is essentially partially broken down fuel,
and it can be recycled and then sort of chucked
on the fire later on when you might need it.
So, if you're going to be doing a high intensity crit race,
or a time trial, or you're trying to go
as fast as you can in a sportive,
with lots of hills in it,
then carbohydrates are going to be required
to get your full potential out of your body.
However, if you're going to be doing a week-long event,
or a long 300 kilometre audax at a steady pace,
then being able to utilise fat
and put fat to good use,
could well be very beneficial.
For weight loss though,
it's as simple as just being in an energy deficit.
You need to consume less energy
than you burn in order to lose weight.
And, well not everyone wants to win the Tour de France,
or do a bike race.
People have different motivations,
so if you're motivations to lose weight are for health,
or for aesthetic reasons, that's perfectly legitimate,
and in that case, ketogenic diet could well be worth trying.
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So how could cyclists integrate a ketogenic diet?
Well, one solution could be
to use it as part of a longer-term training plan.
So you'd have a block of low intensity training,
where you have a ketogenic diet,
in order to try and lose some weight,
get leaner, improve your body composition,
and make race weight.
And then this would be followed
by a period of higher intensity training,
perhaps some racing as well,
where you're fueling that higher intensity period
with carbohydrate.
Basically for athletes in the northern hemisphere,
it would kind of make sense to do this in winter,
but proper peer reviewed thorough studies
into this kind of approach are limited at this stage,
and haven't really been done.
Although anecdotally, I'm aware
that some professional cyclists
have tried this in the world tour,
albeit with mixed results.
Many pro cyclists do something
called periodizing carbohydrate,
but this is completely different.
It involves consuming carbohydrate and fuel
when you really need it,
so on hard training days where you're racing,
or doing lots of intervals.
And on rest days, not eating as much carbohydrate.
So, well today's a rest day for me,
so I'm having a black coffee rather than a cappuccino.
Periodizing carbohydrate in this way
doesn't get you into a state of ketosis.
In order to achieve that,
you need to go very low carb
for a long-term period,
and you only achieve ketosis
after a few days of doing it.
Another potential advantage could come
in the form of reduced gastric distress.
Athletes often struggle with tummy issues
when trying to eat enough in long endurance events,
but becoming fat adapted would mean
you wouldn't have to eat as much.
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So what about supplementing with ketones?
Well there's a lot of ketone supplements available
on the market at the moment,
and the technical term is exogenous ketones,
and the idea here is
that you consume some ready-made ketones,
rather than waiting for your body
to get into ketosis, and make the ketones for you.
The theory behind this is that it provides the body
with additional energy sources for fueling.
You often hear figures quoted
that humans can process between 60
and 90 grammes of carbohydrate per hour,
and by supplementing with ketones,
you're providing an additional fuel source
that's metabolised in a slightly different way.
And I actually went into more detail on this
in the GCN Show a couple of weeks ago,
so if you want to find out more about it,
we'll include a link to that episode
at the end of this one.
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Right, well I hope you found this interesting
and informative, and ultimately I'm not saying keto diets
are good or bad.
Quite simply there just hasn't been enough studies
or evidence published on it yet,
to fully understand the benefits and limitations of it.
And if you're number one goal is losing weight,
or trying to get super lean,
rather than trying to win super high intensity bike races,
then it could be well worth a go.
And keto diets is a massive subject,
and the science is ongoing,
so if you like this kind of content,
then give it a thumbs up, share,
and subscribe to GCN,
and let us know in the comments
what you'd like to see us do in the future.
And to see more information on exogenous ketone supplements
and ketone esters, you can click down here.