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Do You Need Carbs Pre Workout on Keto? – Thomas DeLauer
Ketosis is Glycogen Sparing
Study published in the journal Metabolism profiled 20 ultra-marathoners and ironman distance triathletes age 21-45 who were top competitors in running events of 50 kilometers (31 miles) or more
One group consumed a traditional high-carbohydrate diet, and the other a low-carbohydrate diet for an average of 20 months
On day one, the athletes ran on a treadmill to determine their maximum oxygen consumption and peak fat-burning rates – on day two, the athletes ran on a treadmill for three hours at an intensity equal to 64% of their maximum oxygen capacity
On average, the low-carb runners’ peak fat-burning rate was 2.3-fold higher than the rate for high-carb athletes: 1.5 versus .67 grams per minute
Glycogen finding: Despite their low intake of carbs, the fat-burning athletes had normal muscle glycogen levels at rest
They also broke down roughly the same level of glycogen as the high-carb runners during the long run, and synthesized the same amount of glycogen in their muscles during recovery as the high-carb athletes
Why is This
There were no differences in pre-exercise muscle glycogen concentrations, the rate of glycogen utilization during exercise, and the rate of glycogen synthesis during recovery.
Proves that chronic keto-adaptation in elite ultra-endurance athletes is associated with a robust capacity to increase fat oxidation during exercise while maintaining normal skeletal muscle glycogen concentrations
Rates of muscle glycogen synthesis in humans are highest when large amounts of carbs are consumed immediately post-exercise, yet the keto athletes had similar rates of glycogen repletion compared to the high carb athletes, despite receiving a negligible amount of carbs after exercise (4 vs 43 g) and more fat (31 vs 14 g)
When no carbs or energy is provided after prolonged exercise, a small amount of muscle glycogen synthesis occurs presumably due to hepatic gluconeogenesis providing a source of glucose for glycogen
The question then arises is what is the carbon source for glycogen synthesis in the absence of carb intake post-exercise?
It’s believed that lactate and/or glycerol, which were two-fold higher at the end of exercise in low carb athletes (and then sharply decreased during recovery), may have provided a source of carbons for glycogen synthesis during recovery
Lactate conversion to glycogen could occur directly (lactate glyconeogenesis) or indirectly via the Cori cycle
Could be that lactate rapidly replenished liver glycogen and it has an ability to maintain hepatic glucose output in the face of limited exogenous carb intake
https://www.sciencedirect.com/science/article/pii/S0026049515003340
Always Have Glycogen
Regardless of how low your carb intake is, your body will always be able to manufacture the glucose that in requires via gluconeogenesis
As mentioned, many believe that “you need to eat carbs to survive,” – you don’t need to eat any carbs to survive as your body needs carbs in the form of glucose and glycogen, and it will get this via survival mechanisms like gluconeogenesis
During gluconeogenesis, the liver (and occasionally the kidneys) turns non-sugar compounds like amino acids (the building blocks of protein), lactate, and glycerol into sugar that the body uses a fuel
When glycogen is low, protein intake is high, or the body is under stress, amino acids from your meals and your muscle become one of your main energy sources
Thanks to gluconeogenesis, the portions of the brain that need glucose (and your muscles) get a steady supply, even when your carb intake is very low
https://chem.libretexts.org/Core/Biological_Chemistry/Metabolism/Anabolism/Gluconeogenesis