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Is the ketogenic diet suitable for athletes?

keto diet

 Article originally published on

Does running on fat optimize its performance? How to keep without sugar?

Holyfat explains the principle of the ketogenic diet and helps you understand how fat can become your fuel of choice to achieve your athletic performance!


First, what is the ketogenic diet?

 Used for more than 90 years, especially for therapeutic purposes (in the context of epilepsy, diabetes or cancer for example), the ketogenic diet is based on a simple principle: minimize carbohydrate intake in the diet so that lipids take the lion's share.

Today, ANSES (National Agency for Food, Environmental and Occupational Health Safety) recommends the following distribution for the daily ration of a healthy adult:

  • Proteins: 10 to 20% of total energy input (AET)
  • Lipids: 35 to 40% of the AET
  • Carbohydrates: in addition to the ration, either 40 to 55% AET, with less than 10% of simple sugars (excluding lactose) and sweet products.

For an athlete, these needs may vary, depending in particular on the sport practiced, its frequency / intensity, in addition to specific individual needs, but it is often the lipids that are reduced in favor of carbohydrates (the famous pasta dish racing, you know this one).

In the ketogenic diet, the breakdown is totally different! Exit sugars, hello fat. In order to enter a state of ketosis (you will understand), it is necessary to redistribute the cards to consume only 5% of carbohydrates (i.e. max 20g / day, which remain essential for certain so-called strict gluco-dependent cells, such as Red cells). There is another similar diet but a little less strict in terms of carbohydrate distribution: LCHF, "low-carb, high fat". Same principle except that the authorized part of daily carbohydrates is rather of the order of 20 to 50g.   

 Why "ketogenic"?

 When you wake up in the morning after a good night's sleep, and you ate your pasta dish at 19 p.m. the night before, your meal is in your socks and your blood sugar level is low. So that you do not cuddle before the next meal and to reserve the use of glycogen for cells that cannot do without glucose, several metabolic pathways are put into action.

La ketogenesis is one of them, it allows the production of ketone bodies in the liver from the lipids stored in our adipose tissue. These ketones are used by muscle cells, organs, and neurons. They are the privileged source of the renal cortex and the heart and can provide, during a period of prolonged fasting, up to 75% of the energy consumed by the brain (the stores of glucose in the form of glycogen in the liver or the muscles allow to provide the remaining 25%).

The ketogenic diet therefore takes its name from this metabolic pathway, which allows the body to use fat for energy instead of carbohydrates.


OK, but what's the point of following this diet if my body adapts anyway?

Let's make a comparison between what happens in a person who eats "normally" and a person who follows a ketogenic diet.


Yes you can tell yourself that you just have to eat your pasta and go for your marathon, the ketones will take over anyway. Yes but no, it is not that simple! Nature is well done but it is not open bar either. 

In reality, you have to come back to what happens when your body mainly carbs on sugars, so as part of a so-called normal diet (with 40 to 55% of carbohydrates in your ration).

Situation A: Normal diet, balanced diet recommended by ANSES  

After your meal, your blood sugar will increase. The more carbohydrate-rich the foods it contains, the more your blood sugar will rise. Add to that the ability of a food to raise your blood sugar, which is called the glycemic index (GI). A meal rich in high GI foods and low in fiber, lipids and proteins (for example: fruit juice, baguette, honey, or for example before a race: sports nutrition product like gel), will make your blood sugar take off very quickly . But it will come down just as quickly, and that's when you fall on a bone if you don't have refills at hand: sweating, palpitations, dizziness, nausea, tremors, intense fatigue… Hypoglycemia is watching you Huguette !

This is even more valid in the context of sport because energy expenditure is increased tenfold, the effort provided being much more intense for our body. We are no longer at cruising speed, we have to refuel the boiler to run the engines (you too visualize the Titanic? Poor Jack… but that's another debate). This is why when you start to consume gel, fruit paste or an exercise drink, it is necessary to take it again every 45 minutes, otherwise watch out for slack. But when you run or pedal for hours and have to recharge the battery nonstop with sugar, hello sickness and goodbye bowels.

Let's go back to your blood, soaked in glucose after a meal. Your pancreas will release insulin, the hormone responsible for regulating this sugar level, so that it allows glucose to enter the cells that need fuel (and also prevent your blood from turning into syrup). The excess will be synthesized into glycogen in the liver and muscles (via glycogenesis) to create glucose stores, the rest will be transformed into triglycerides and stored in your fat cells via lipogenesis (literally, the manufacture of fat). Note that as long as your cells have sugar, you will not draw on your fat reserves to continue the effort ... Obviously, if you play sports to lose your brioche, this is not the best method!

These famous fat reserves will be used during the fast in a resting situation, the loop is closed. On the other hand, during the effort, the body does not have time to adapt, it needs energy immediately to maintain the pace: you must therefore refuel frequently to continue your competition or your training. 

Situation B: Ketogenic diet, fat from fat

While on a ketogenic diet, you consume 80% fat, protein and a little bit of carbohydrate, the essentials. Note that carbohydrates, unlike proteins or lipids, are the only non-essential nutrients in large quantities since our body is able to synthesize it (it is nevertheless for our red blood cells or our neurons and is not not to be completely removed, of course).

Your body will therefore be starved of carbohydrates for a long period of time, not just a few hours. He will then gradually enter what is called the state of ketosis. Ketosis is when the body switches fuel and switches from glucose to ketones. The few grams of daily sugars remaining are therefore intended for our glucose-dependent cells, which cannot feed on ketone bodies. It will take approximately 2 to 3 weeks for an individual to enter the ketogenic diet, or LCHF, to enter this state of ketosis. It will also go through several phases that are not necessarily pleasant at first, while the body gets used to and is weaned from sugar: fatigue, nervousness, nausea, etc.

Once this period has passed, the transition will be complete and the individual, known as “adapted keto”, will naturally consume fat as fuel rather than carbohydrates! It will then be much more easily sated and in good shape since it will no longer be subject to variations in blood sugar (and therefore exit the little bar at 11am, the craving for 16pm, the desire for chocolate in front of the TV). Often, he will lose weight, as he will draw on his fat stores to provide energy for his muscles and organs.

Note that there is a new trend that is emerging, we speak of "Metabolic flexibility". We'll talk about this in a future post, let's say it's the next step, once you're fully keto-friendly and still want to get some carbs back on.

The ketogenic diet and exercise

You begin to understand the value of a ketogenic diet but do not feel ready to follow one for all that, because it is true that it is quite drastic and that it requires a total reorganization of consumption habits.

So is it interesting to look at fat only in the context of sport?

Yes my good lady. Already, let's compare the composition of a sweet gel and a snack with good fat, on the off chance Holyfat (good ok, that seems moderately objective but we are the only ones in France to offer this type of product, we do not have so much choice in the end, it's not my fault as Lolita would say).

In your gel, lambda brand, you have on average 70% carbohydrates, often in the form of glucose and maltodextrin syrup, less than 0,5% fat and less than 1% protein. The rest is water, salt and a few milligrams of vitamins and fatty acids. For a pouch of about 30g, you have the equivalent of 90kcal in energy.

At Holyfat, we work on the basis of the ketogenic diet. Our product contains 70% fat (and vouchers: nuts, Almonds, TCM oil), less than 3% carbohydrates (naturally included in oilseeds) and 20% protein. A 28g bag Provides you on average 200kcal, twice as much as a gel for the same amount, and without causing any variation in blood sugar. A good dose of energy, constant, which allows you to last a long time without craving and without loss of energy.

Indeed, even if you are not keto adapted (e), consuming fat before and during your outing instead of sugar will protect you from any change in blood sugar and will allow you to go the distance and the duration with the fishing of the first kilometers! However, we advise you to keep a source of carbohydrates close at hand and consume it in the last hour of effort to give you a last little boost before the finish line (and recharge your glycogen reserves) . Of course, all of these dietary trials should be done during training, not on the day of a competition, each with their own reactions and habits.

In a nutshell, good fat is life !

So do not hesitate to consume it, on a daily basis if you want to start a ketogenic diet or during an effort, especially long-term!

Note however that in the context of certain physiological or pathological conditions (pregnancy, breastfeeding, diabetes under insulin, ...), the ketogenic diet is not recommended. If you want to start it, do not hesitate to call on your doctor or a dietitian to support you and guide you in this dietary transition.

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