How to improve your metabolic flexibility through diet

Metabolic flexibility defines the ability of our metabolism to switch from one energy fuel to another, from carbohydrates to lipidsas our ancestors once did during periods of food shortages. During periods of scarcity, their body switched to ketosis mode: a metabolic state in which the body produces and uses ketones as its primary fuel.

“This metabolic flexibility, this ability to move from glucose to ketones, allowed our ancestors to remain functional in all circumstances, for example, after several days without game or gathering, during long migrations or harsh winters.explains Marion Kaplan in her new book, Keto-biotic. In other words, Homo sapiens was able to adapt and developed an emergency energy system, like equipping a house with a generator to have electricity in the event of a power outage. He had to find an alternative fuel, and that fuel was ketones. »

What is ketosis

Usually cells use glucose as fuel. But when carbohydrates are lackingthe liver can transform lipids into ketone bodies, the use of which by cells then replaces glucose. “These molecules do not just fuel the brain, the heart or the muscles: they optimize energy production, protect cells and participate in many vital functionssays Marion Kaplan. Reactivating this ancestral pathway through targeted nutrition or fasting means regaining our metabolic flexibility and transforming our relationship with energy, hunger, mental clarity — and overall health. »

These ketone bodies are essentially:

• beta-hydroxybutyrate (BHB), the most abundant ketone (around 78% in proportion in the blood);
• acetoacetate (approximately 20%);
• acetone (around 2%), largely eliminated by the lungs, which can explain the particular breath of certain people in ketosis.

How to measure your ketosis

To find out if you are in ketosis, you can use urine strips that detect ketones in the urine, or a blood sensor for blood sugar and ketone levels.

Why metabolic flexibility is important for good health

The concept of metabolic flexibility explains insulin resistance: when the body has been exposed for many years to high levels of insulin, due to a diet high in carbohydratesthe cells react less and less to the insulin message. The pancreas produces even more insulin, and the cells become more and more resistant.

“The most insidious problem of insulin resistance is the impact of this hormone on lipolysis, said Marion Kaplan. Insulin naturally blocks the release of fatty acids from fat cells. » As insulin levels remain high, adipocytes refuse to release their free fatty acids, which are the molecules essential for the production of ketones by the liver. Result: the body loses its metabolic flexibility. Insulin resistance also complicates weight loss : as long as insulin remains high, adipocytes retain their fatty acids, making any mobilization of fats very difficult.

Insulin resistance, an underestimated danger

Sedentary lifestyle, a diet rich in carbohydrates and ultra-processed foodsstress, are all factors that promote insulin resistance. For Professor Benjamin Bikman, author of Insulin resistancethis disorder goes well beyond prediabetes: “Insulin resistance plays a role in a surprising number of very serious chronic diseases, including problems with the brain, heart, blood vessels, reproductive organs, and more. Much more than a simple inconvenience, it is a serious illness when left untreated. Most people who experience insulin resistance will eventually die from heart disease or other cardiovascular complications. Others will develop Alzheimer’s disease, breast or prostate cancers, or other life-threatening illnesses. »

How to regain better metabolic flexibility

In his book Keto-bioticMarion Kaplan proposes several concrete levers.

• Practice intermittent fastingfor example by skipping breakfast: fasting leads to launching the process of ketone body formation. The longer it is prolonged, the more your body uses these ketones. For example, if you eat at 7 p.m. in the evening and wait until 11 a.m. the next day to eat, this allows for a 16-hour fast, corresponding to 16:8 intermittent fasting. “Fasting is the most direct path to ketosis”says Marion Kaplan.

• Reduce your carbohydrate intake (without necessarily going as far as the ketogenic diet) and enrich your diet with ketonesfor example with MCT oil which provides C8 fatty acids. “C8 and C10 fatty acids have an interesting property for us: they are very quickly converted into ketones by the liver, regardless of the level of carbohydrates in the diet. »

Fasting is the most direct path to ketosis

Frequently asked questions

What is metabolic flexibility?

It is the body’s ability to switch between two energy sources — carbohydrates and fats — as needed. Good metabolic flexibility allows you to better manage your blood sugar levels, daily energy and weight gain.

Is intermittent fasting effective for improving metabolic flexibility?

Yes, it is one of the most direct levers. A 16-hour fast (for example from 7 p.m. to 12 p.m. the next day) is enough to trigger the production of ketone bodies and retrain the body to use fat as fuel.

Should you follow a strict ketogenic diet?

No, it is not essential. You can reduce your carbohydrate intake without going as far as the ketogenic diet.

Metabolic flexibility and weight loss: what is the link?

Better metabolic flexibility facilitates lipolysis, i.e. the body’s ability to draw on its fat reserves. This is a key factor for lasting weight loss, unlike restrictive diets that do not address insulin resistance.

To find out more: Keto-biotic