#52 Ketosis and Exercise Performance (SCIENCE EXPLAINED)

Siim Land (0:00)

Man, you're doing the keto diet, you're gonna die.

SPEAKER_2 (0:04)

You're gonna die, that's what's happening.

Siim Land (0:07)

You need carbs before the workout to give yourself energy. During the workout to not debunk.

After the workout, you need carbs to recover from the exertion. And at any other time of the day, you need carbs as well, because otherwise, you're gonna hit the wall and go into starvation mode.

SPEAKER_2 (0:24)

Starving.

Siim Land (0:25)

Now, this can be quite misinterpreted and taken out of context.

SPEAKER_2 (0:31)

By practically, you mean not really.

Siim Land (0:34)

Can you train hard on the ketogenic diet?

How does ketosis affect your performance? Will your muscles dissolve into a big chunk of wobbly jello if I don't eat carbs after working out?

This and many more in today's Body Mind Empowerment Podcast. My name is Siim Land and in today's episode, we're going to go into the science of how keto-adaptation changes the way your body uses fuel sources at different intensities of exercise. We're going to talk about endurance, CrossFit, HIIT cardio, bodybuilding, powerlifting, gymnastics, and walking your dog as well. So let's get on with it. Body Mind Empowerment.

SPEAKER_2 (1:16)

Get stronger, faster, smarter, quicker, friendlier, more helpful, more driven.

Siim Land (1:22)

Everything the body needs.

SPEAKER_2 (1:23)

Control your mind.

Siim Land (1:27)

First of all, let's start from some of the basics. There are several fuses sources the body can use. Glucose from carbohydrate and sugar molecules is the default fuel because it's fastly absorbed and it gives instant energy. Burning carbohydrates in the Krebs cycle is called glycolysis, which creates pyruvate that then gets converted into ATP. Fat acids from dietary fat or your own body fat go through beta oxidation, which creates ketone bodies, triglycerides and other phospholipids. Compared to other macronutrients, fatty acids yield the most ATP on an energy per gram basis, which makes them the most abundant fuel source in animals. Ketone bodies are byproducts of fatty acid metabolism that provide an alternative fuel to glucose. They can actually be seen as the fourth macronutrient after protein, carbs and fat because of their unique metabolic substrates. Then there are some other fuel byproducts that can be converted into energy through some pathway or another such as lactate, glycerol, protein, branch chain amino acids and many more. You're always burning a mixture of different energy molecules, whether from glucose, ketones, fatty acids, lactate and many more. What proportion of each you're currently using depends on the intensity of physical exertion, your overall metabolic condition and your degree of keto adaptation.

Since the 1960s, it was thought that a high carbohydrate diet maintained physical performance and muscle glycogen by preventing fatigue, which was induced by muscle glycogen depletion. Basically, you run out of muscle glycogen and your body goes into an energy crisis. Therefore, you need to eat a lot of carbs. I've had him spaghetti. The simplistic view of how your body uses fuel is that you're burning primarily fat at lower intensities of exercise and at higher levels of exertion, you start using more glycogen and glucose. This is known as the crossover effect with a progressively increased contribution of carbs as a fuel source. It promotes the notion that you can't perform high intensity sports while eating a low carb keto diet. In reality, your body needs glucose from carbohydrates under certain metabolic conditions. At other times or during periods of starvation, the body will come up with many alternatives that are actually much more sustainable and suitable for certain situations. When you go on a low carb keto diet, you're gonna alter your metabolism by entering into a state of nutritional ketosis. This is characterized by higher rates of fat oxidation, a reduction in the body's glucose demands, sparing of muscle glycogen and virtually no protein metabolism. With carbohydrate restriction, your liver starts producing more ketone bodies that can come from dietary fat sources, or from stored adipose tissue. These ketone bodies like acetone, acetoacetic acid and beta-hydroxybutyrate or BHB will provide an alternative fuel source to glucose.

Even though the brain and other vital organs need about 100 to 120 grams of glucose every day, keto adaptation enables ketone bodies to cover nearly 70% of that required energy. The remaining energy the brain needs can be covered by converting fatty acids into glucose through a process called gluconeogenesis.

In fact, after keto adaptation, your body's overall glucose demand will decrease even more, and you don't even need that much glucose. In 2016, Jeff Volek and Steven Phinney did a study called FASTER, which stands for Fat-Adapted Substrate Oxidation in Trained Elite Runners. The study showed that ultra endurance athletes who had keto adapted for 9 to 36 months showed extraordinarily higher rates of fat oxidation. Here are the main findings of the study. First, they were using fat for fuel even at the intensities of 70 to 80% of their VO2 max, compared to the 55% of the high-car control group. Secondly, peak fat oxidation was 2.3-fold higher in the low-car group, and it occurred at a higher percentage of VO2 max. Thirdly, during submaximal exercise, fat oxidation was 59% higher in the ketogenic group. And fourth, there were no significant differences in resting muscle glycogen and the level of glycogen depletion even after 3 hours of exercise. Over the course of a 3-hour run at 65% of VO2 max, the low-car group was burning 30% more fat and 30% fewer carbohydrates than those who ate high-carb. Some of the subjects on the keto diet actually burned 98% only fat and only 2% glucose at 65% of intensity. Keep in mind that fat oxidation doesn't refer to losing body fat directly, it refers to what proportion of fatty acids gets burnt in the KREP cycle. And in the case of these low-carb athletes, they were able to fuel their exercise with primarily fat.