Coach Jack talks about what happens to the ketogenic Athlete when he hits the gym for some intense workouts.
If you look at blood glucose readings right after an intense fasted/keto workout you will see a pretty dramatic rise in blood sugar.
Is it because you eat a bunch of carbs during the workout? Nope. Here is what happened from start to finish on a day I did a keto workout up to the point of the last reading which showed high glucose.
7:30 am – Breakfast of 4 eggs and coffee with 1/4 cup HWC
11:17 am – took glucose reading and left for gym
12:00 pm – Workout
5 reps @ 135
5 reps @ 185
4 reps @ 225
3 reps @ 275
2 reps @ 295
1 rep @ 315
WOD (Workout of the Day – crossfit term)
3 rounds for time
25 lateral hops over barbell
25 Mountain climbers
15 Hang power cleans at 95lbs
Time: 4:04 RX’d (Means I did the workout as prescribed or as it was designed)
Extra work: Ring pushups (pushups but instead of hands on floor you have them on gymnastic rings hanging 3 inches from the floor)
1:15 pm – took Second reading
1:20 pm – ate 2 eggs and some brie
2:55 pm – took third glucose reading
So what happened to cause the glucose spike? (typically 3 mmol higher than baseline)
When you workout with any level of intensity you need Glucose. When you do Anaerobic activities like heavy explosive lifts or high intensity workouts you have to utilize the glycolytic pathway (pathway that uses glucose for fuel and is responsible for most high energy/explosive activity). Many anti-keto fitness types would lend you to believe that low carbers can’t perform these types of workouts or suffer at them because they are unable to use the glycolytic pathway. This simply is not true. I can tell you that I was one of the fastest people to finish this workout today and I also had the heaviest front squat in the class. I did not suffer one bit and I can assure you I had zero carbs for fuel.
The fact is that you must and will use the glycolytic pathway. It is going to happen and the body will use it not matter what the “fitness experts” tell you. It is the second pathway to get used in a chain of pathways and gets used regardless of the fact that you do or do not eat carbs.
So where does the glucose for the glycolytic pathway come from? Great question. I have 4.0 to 5.0 mmol/L of glucose sitting in my blood. Why on earth would I not be able to use this? I can and I did. Here is exactly what happened:
I start doing heavy front squats and this requires glucose for that glycolytic pathway so the muscles start pulling it out of the blood. But won’t I go hypoglycaemic? Well if I wasn’t full of ketones to run my brain, yes I would likely get light headed and pass out, but since I am full of ketones, my brain runs very well on them while my blood sugar is being used to fuel my exercise. Now the blood sugar can’t continue to drop without actually risking some issues so the low levels will signal cortisol. Cortisol starts yelling at the pancreas to release glucagon. Glucagon’s job is to get energy out of cells and into the blood. It does this by signalling the liver to start that wonderful process called Gluconeogenesis or GNG for short. This process kicks into gear and starts converting glycerol from fat as well as amino acids from the amino pools or if those are not adequate it will start pulling them from lean mass. This process supplies all the additional glucose to keep the blood glucose level up in addition to providing all the glucose I need to finish the WOD well ahead of most of the other carbed up Crossfitters.
Now what happens when I stop working out? GNG doesn’t stop right away. It takes time to ramp down so it keeps turning amino acids (protein) and glycerol into glucose until it has time to ramp down. How long does that take? I honestly don’t know. I do know that because of this you see that we have a huge rise in blood sugar that is nearly 3.0 mmol/L above my baseline. This was also detailed in the FASTER study conducted by Dr. Stephen Phinney. They tested the muscle glycogen of low carb athletes and carb fuelled athletes post workout and found that they had nearly identical levels. This means that the infamous “carb load” after a workout is not necessary as most typical carb fuelled gym types would have you believe. The idea is that the carbs spike insulin and this helps get the protein into muscle and restore lost muscle glycogen. Well you clearly don’t need to “Carb up” to get glycogen into muscle and I speak about the protein getting there coming up. 🙂
What is the effect of blood sugar this high? That is right. Insulin response to get it back down. So while exercise is great, I get an insulin response right after which means I am not losing weight anymore. What else is going on here you ask. Well since I’ve already laid out the fact that all that glucose likely came from amino acids and amino acids likely came from your lean mass, and you already are going to have an insulin response, what can we do to maybe mitigate some of the amino acids that were taken and also take advantage of that ever so Anabolic (muscle building) effect that insulin has? Eat some protein!!!!
Eating protein at this time is ever so optimal. It will get shunted directly to where it needs to go, replacing the amino acids taken from stores during GNG and because you already had an insulin spike coming, eating protein now will have a net zero impact on the days total insulin load. Bonus.
Less than 2 hours after a very high glucose reading, my blood glucose level is almost right back to where it had been prior to any exercise. This likely means that all insulin is pretty much out of my system and I am right back to using my body fat for fuel. Isn’t that just the neatest ever.
Another little cool idea is that the protein actually helps the blood glucose lower faster. The idea behind this is the fact that because protein has an insulin response but has no actual glucose load with it, that it will lower blood glucose and stabilize it. Since the insulin comes but the protein doesn’t actually add any extra to the mix, this seems to make sense. I tested that theory. Below is a pic of my blood glucose 2 hours after a workout on a day where I didn’t have anything to eat after the workout. Notice that it is not nearly as low as todays. I can’t say for sure that is the reason but since the workload that day was similar and I eat the same thing every day, the hypothesis seems sound. Take a look.
I hope you found this informative. Science is fun. 🙂