Your brain is an energy hog. It makes up only about 2% of your body weight, but it uses about 20% of the energy you burn at rest. Most of that energy usually comes from glucose, but your brain has another fuel source, ketones.
Your liver makes ketones when glucose availability drops and your body starts using more fat for fuel. That happens during fasting, prolonged exercise, carbohydrate restriction and ketogenic diets.
But ketones do more than give your brain another fuel source. Beta-hydroxybutyrate, or BHB, also acts as a signaling molecule with positive effects on inflammation, oxidative stress, energy metabolism and brain function.
Ketones are useful but I don’t think you need to stay in ketosis all day, every day. I want metabolic flexibility. I want to use glucose when I need glucose and ketones when I want ketones.
And you don’t have to spend your life fasting or eating a strict ketogenic diet to raise your ketones.
Your Brain Can Run on Ketones
Your brain normally gets most of its energy from glucose. When glucose availability drops, your liver makes ketones from fatty acids. The main ketones it makes are beta-hydroxybutyrate and acetoacetate. Your brain can take those molecules up and use them to make energy.
That gives your brain another fuel source. Ketones are a cleaner-burning fuel for your brain. They get into your mitochondria and give your cells a steady supply of energy while reducing some of the oxidative stress that comes with glucose metabolism. That’s one reason raising ketones can make you feel significantly more alert, focused and energized.
BHB also reduces inflammatory signaling in studies, including ones looking at brain inflammation.
Check out what it does in Alzheimer’s. Amyloid-beta is one of the hallmarks of Alzheimer’s disease, and the small amyloid-beta clumps called oligomers can trigger inflammation in the brain. In a 2023 study, researchers exposed human brain immune cells called microglia to these amyloid-beta oligomers. BHB reduced the inflammatory response and helped restore the cells’ ability to clean up cellular debris.
We also have new human data. A 2026 randomized trial followed 60 people with early-to-mid-stage Alzheimer’s disease for six months. They tested a ketogenic diet with intermittent fasting against standard care. The intervention group had better cognitive outcomes than the standard-care group. The combination of a keto diet and fasting would have kept blood ketones elevated for more of the day, giving their brains a steady supply of an alternative fuel.
This is big. Alzheimer’s is one of the Four Killers I described in my longevity book, Super Human.
Metabolic Flexibility
I’ve used ketosis for years, and I think it has tremendous value. But I don’t want to lock myself into one metabolic state. There are times when I want to burn fat and produce ketones, times when I want carbohydrates available for hard training, and times when I want to eat a meal without worrying about whether it fits perfectly into a ketogenic diet. I want metabolic flexibility.
A strict ketogenic diet usually means keeping carbohydrate intake very low, often around 20 to 50 grams of net carbs per day. That can work, and I’ve used it myself. But keeping carbs that low all the time can trash your hormones long-term.
Carbohydrates also have a place in high-intensity exercise because your body can use glucose quickly when energy demand spikes.
I don’t see ketosis and carbohydrates as opposing teams. I want the ability to use both.
In the full article, I’ll show you:
How a specific oil can raise ketones without a keto diet
A drink that raises ketones even if you’re eating carbs
How I use ketones for more energy
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