Lately I’ve seen many bloggers, influencers and friends move thoward a carbohydrate free-diet and talk about the benefits of ketosis and steady blood sugar. While training on a low carb-diet from time to time will help your body learn to burn more fat, I believe an extreme approach, like a keto diet might be a bad idea.
The road to a carbohydrate free diet is often based upon different food blogs, small-not so conclusive studies and a mixture between fact and assumption. The truth is that within the training science community, there is a consensus about the fact that
1. carbohydrates reduces recovery time
2. carbohydrates will help you preform better
3. you can train your body to burn more fat, even though you have a high carbohydrate intake. Let me take you trough why.
Carbohydrates and performance
That carbohydrate intake further performance for runners, cyclists(1) as well as when setting a new PR at the gym(2) may be new to you, but within sport science it’s common knowledge. (Don’t listen to me, see the list of links below to the studies I refer to, as well as the US and Australian dietary recommendations)
When running 10 km, running an ultra or climbing a long day at the crag, various complex processes in your body start. I’m going to try to keep this as simple as possible. The muscle cells in your body will start to break down, creating a need for protein to replenish these damaged muscle cells.
Hidden between your muscle fibers and in your liver you’ve also got what is called glycogen stores. Glycogen, is the final version carbohydrates take after intake, before they are used up. The body can store about 2000kcal of glycogen for later use when needed.
You’ve also got a HUGE reserve of fat to be used during activites.
Think of it like this, every time you are hungry you have to get up from the sofa, walk to the fridge, turn on the stove and cook some food. It’s a good and economic way to feed yourself. Thats the fat.
Some days are more stressful. You don’t have time to cook food, but instead order food delivery to your home, or just eat a fast salad you’ve bought. Thats the glycogen.
The glycogen are there, and is ready to be used during the most intense, long or hard sessions, and the stores get depleted fast. For someone running or being active every day, these stores generally get depleted on a regular basis, and needs to be restored for the muscles to be able to amass the energy they need to preform their best. Multiple stidies has shown that a combination of protein and carbohydrates after a trainig session does help recovery (3)(4)(7).
Fasted training and fat adaptation
But since our fat stores are huge, wouldn’t we want to furter the bodies use of fat? Of course! But this can be done, even if you have a medium or high carbohydrate intake(8)(10,11).
- Do activities pre breakfast in a fasted state.
- Do activities 4-6 hours after your last meal.
After your workout, you can refill with protein and carbohydrates, making your body ready for an afternoon run or an evening at the crag.
Why shouldn’t I always train on a low carb diet then? Well, as mentioned earlier, carbohydrates helps recovery, it furthers preformance and does also help keeping you motivated if the intake is well planned during a longer event.
In ultra running and cycling races, there has been shown that athletes on a low carb diet do have a more efficient economy – burning more fat and less glycogen. The tradeoff though, seems to be preformance, as they don’t seem to preform better at races than a runner, eating a mixed diet(5). There is even a study showing that a low carb diet could give negative effects over all(6). “However, LCHF also increased the oxygen (O2 ) cost of race walking at velocities relevant to real-life race performance”
As for health risks with a low carb diets?
A study on rats showed that a keto diet could cause scarred heart tissue.
“In the ketogenic group, the rats demonstrated an increase in the ketone β-OHB levels and a resulting activation of the gene Sirt7, inhibiting the biogenesis of mitochondria. Furthermore, when this pathway was translated to human cultured cells, it led to apoptosis (cell death) of cardiac cells and fibrosis (scarring).” (9).
Liver problems. With so much fat to metabolize, the diet could make any existing liver conditions worse.
Constipation. The keto diet is low in fibrous foods like grains and legumes.Harward Health
How much should i eat?
Eat a mixed diet goddamnit!
The U.S. Olympic Committee Sports Dietitians and The Australian Institute of Sport both agree that daily carbohydrate needs increase when training volume increases. This is the essence behind nutrition periodization. As a matter of fact, it’s recommended that athletes consume between 1 and 1.5 grams of carbohydrate per kilogram of bodyweight (0.45 to 0.68 grams per pound) for recovery. The actual number depends on length and intensity of the workout.
For a 130-pound female athlete, that equals 59 to 89 grams of carbohydrate. Translation: If she ran 30 to 45 minutes, she would need to eat 59 grams of carbohydrate afterward. If she rode 3 hours, she should eat 89 grams of carbohydrate as part of the recovery meal.https://www.active.com/nutrition/articles/the-role-of-carbohydrates-in-recovery
One thing I’d like to add is that even a keto diet has I’ts place. It has been shown to help control blood sugar levels for diabetes patients as well as help patients lose weight – If you need help with this, meeting up with a medical dietist could be a good idea(12, 13).