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What Type of Workout is Best on a Low Carb or Ketogenic Diet – Thomas DeLauer

*Carbohydrate content falls during exhaustive exercise and muscle fatty acid oxidation increases with a concomitant increase in blood ketone concentrations* (1,2)

Anaerobic/Aerobic and Intensity

Your body requires different types of fuel, depending on the intensity of the exercise – as the intensity of exercise increases, the body shifts its fuel preference from blood-borne fatty acids (and glucose) towards those of intramuscular triglycerides (IMTG) and glycogen

At moderate-to-high exercise intensities (less than 75% of maximal oxygen uptake, V02max), muscle glycogen is the main source of energy provision (Egan and Agostino, 2016) (2)

Ketones are burned in the mitochondria of our cells only, which means it requires oxygen – glucose also is burned in the mitochondria of our cells in the presence of oxygen, but when glucose is burned in the mitochondria, it produces more ROS (reactive oxygen species) and free radicals, resulting in damage

However when a cell is working very hard, like our muscle cells when we are doing high intensity exercise, the cells need to make energy at a faster rate than the oxygen can get there, therefore when we are at a higher intensity, we can burn glucose outside of the mitochondria, without the need for oxygen – ketones cannot do this (3)

Burning glucose can be both aerobic (with oxygen) and anaerobic (without oxygen). Ketones are aerobic only. High intensity exercise like the 100 yard sprint or olympic lifting, is purely anaerobic and requires glucose

Low intensity exercise like a walking, jogging, elliptical, cycling, hiking, etc. can be purely aerobic (if done at a low enough intensity)

The purely aerobic exercise will allow ketones to be the dominant fuel burned. When given a choice the brain, heart and muscles will choose ketones over glucose, they can only do this if both are present in the blood (3)

Study – Journal ‘Cell Metabolism’

Study looked at the effects of exogenous ketone administration in 39 high performance athletes to see how the body utilises different forms of energy during exercise

Each of the 39 athletes completed 3 experimental trials consisting of 1 hour of constant load cycling (high-intensity at 75%) – athletes were given a ketone ester (KE), carbohydrate (CHO) or fat (FAT) drink 15 minutes prior to the start of the exercise and 45 minutes into the 1 hour trial

Athletes who ingested the KE drink, were found to display lower levels of lactate, plasma free fatty acids (FFA), glycerol and plasma glucose than those athletes that ingested the CHO or FAT drink, throughout the entire 1 hour exercise trial period

Suggests that KE might have some sort of sparing effect on intramuscular glucose stores, most likely due to the suppressive effect on muscle glycolysis

And suggests that ketones were oxidised as an alternative to pyruvate, reducing the reliance on glycolysis to provide acetyl-CoA needed for the TCA cycle (5)


1) Ketones and Exercise – What You Need to Know. (n.d.). Retrieved from

2) Ketones And Exercise Performance: New Insights. (2017, September 12). Retrieved from

3) Optimize your exercise to burn fat and utilize ketones. – Dr. Steven G. (2017, June 30). Retrieved from



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