Why You Need FAR Less Carbs Than You Think (Especially During Exercise) & Ketones As An "Alternate Fuel", With Dr. Andrew Koutnik - Part 2

Ben Greenfield

Feb 21, 2026

Episode description

Full Show Notes: bengreenfieldlife.com/drandrew2

In this episode, Dr. Andrew Koutnik returns for part 2 of our deep dive into metabolism and nutrition. We explore why you need far fewer carbohydrates than you think—both during daily life and intense exercise—and how sustained blood glucose levels for brain energy metabolism matter more than muscle glycogen stores. Andrew breaks down the different types of exogenous ketones, debunks liver toxicity concerns, and shares groundbreaking research on ketones for sleep quality and sleep apnea treatment from his NASA astronaut studies.

Dr. Andrew Koutnik is a research scientist whose career bridges cutting-edge science, elite performance, and personal experience living with type 1 diabetes for over 17 years. His work focuses on how nutrition, metabolism, and lifestyle can be leveraged to maximize human health, performance, and resilience across diverse conditions—from chronic disease to extreme environments.

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Mindsip insights from this episode:

Limit carbohydrate intake to sustain performance during long exercise

For exercise lasting over two hours, consuming as little as 10 grams of carbohydrates per hour is enough to sustain performance by maintaining blood glucose for the brain.

#carbohydrate

#exercise

Utilize acetoacetate to enhance fat breakdown in adipose tissue

Unlike the more common beta-hydroxybutyrate (BHB), the ketone body acetoacetate appears to uniquely facilitate mechanisms of fat breakdown in adipose tissue.

#fat

#metabolism

Utilize exogenous ketones to improve sleep apnea symptoms

A leading hypothesis suggests that taking exogenous ketones before bed could help with sleep apnea by increasing oxygen uptake per breath and reducing carbon dioxide production.

#sleep-apnea

#supplement

Maintain performance with ketones and lactate in low-carb athletes

Low-carb athletes can maintain performance despite lower blood glucose because higher levels of ketones and lactate provide an equivalent total amount of circulating brain energy.

#lactate

#metabolism

Ensure safety of Ketone IQ at high doses with no liver enzyme impact

Even at daily doses equivalent to ten bottles of Ketone IQ for 30 days, studies on its core ingredient (1,3-Butanediol) found no adverse side effects on liver enzymes.

#liver

#supplement

Utilize exogenous ketones to enhance oxygen uptake at high altitudes

Exogenous ketones can increase oxygen uptake at high altitudes, providing resilience against hypoxia in a similar way to mountain sickness medication like Diamox.

#hypoxia

#supplement

Reassess high-carb diets to prevent pre-diabetes risk

In one study, 30% of lean, high-volume runners on traditional high-carbohydrate diets developed fasting glucose levels consistent with pre-diabetes.

#carbohydrate

#diabetes

Prioritize liver for insulin after carbohydrate consumption

When you consume carbohydrates, insulin's first destination is the liver, not the muscle, to prioritize replenishing glucose stores that protect the brain.