SIGMA NUTRITION RADIO | #545 carbohydrate metabolism, performance & metabolic health- professor Javier Gonzalez
George’s Podcast Reflection Notes. Listened on January 7th 2025
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High glucose levels (above 10 mmol/L) are linked to increased cardiovascular disease risk.
The relationship between glucose levels within the non-diabetic range (4.5-10 mmol/L) and disease risk is less clear and may not be causal.
Blood Glucose and Carbohydrate Intake
People often mistakenly connect a rise in blood glucose solely to carbohydrate intake.
However, various factors, including what’s in the meal and individual responses to standardized carbohydrate amounts, also impact blood glucose levels.
High-Intensity Exercise and Glucose
High-intensity exercise can significantly increase blood glucose levels, even when fasted.
This is due to the liver releasing glucose in response to the exercise stimulus, before muscle uptake increases.
Carb Availability and Athletic Performance
Carbohydrate availability during exercise is critical for optimal athletic performance.
Muscle glycogen is important for multiple reasons including as a fuel, a signaling molecule for force production, oxygen efficiency, and rapid ATP resynthesis.
Intestinal Absorption Limits Carb Burning
The main factor limiting the body’s ability to burn ingested carbohydrates during exercise is the intestine’s absorption rate.
This suggests that the muscle’s ability to use glucose isn’t the bottleneck.
At the start of exercise, muscles primarily use stored fuels like glycogen and intramuscular fat.
As exercise continues, the body gradually shifts to using blood-borne fuels like glucose from the liver.
Ketogenic diets spare muscle glycogen and increase fat oxidation, partly by increasing pyruvate dehydrogenase kinase (PDK) in muscles.
Increased PDK also decreases carbohydrate oxidation, hindering high-intensity performance in endurance events.
Ketogenic diets increase fat oxidation by increasing PDK in muscles.
This also decreases carbohydrate oxidation, creating a trade-off between fuel sources.
Ketone esters during exercise do not reliably enhance performance.
They might even impair glycogen utilization, offsetting any benefits as an alternative fuel source.
Whole wheat bread tends to have a moderate to high glycemic index, while whole wheat pasta tends to have a moderate to low glycemic index.
Whole wheat foods still offer benefits such as lower blood pressure compared to white counterparts, so glycemic index shouldn’t be the sole focus.
