– 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, and click the bell icon, as this will give you a notification, and it helps support the channel. (upbeat music) 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. (light music) – 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. (light music) 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. (light music) 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. (light music) 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. (light music) 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.