Why do I get brain fog when I cut carbs?

Nikkiey walks through what happens to carbohydrates in your body. They're broken down into glucose, which travels through your blood and provides energy to your cells, especially and first of all your brain. Any glucose you don't need right away gets stored in your liver and muscles as fuel in reserve, then brought back out when your body needs energy. In her words, your brain loves carbohydrates and fuels off that energy. When you restrict or eliminate carbs, or just eat very low-carb, that supply runs short, and the fog you feel is the result.

She adds some nuance about low-carb approaches like keto. If you don't eat many carbs, your body can over time adapt and switch to an alternative fuel made from fat, called ketones. But she points out that getting there takes days, even weeks, and eating a carbohydrate breaks it. That's one reason she doesn't see it as sustainable. You don't want to go without carbs for the rest of your life. She also notes that even a single day when you're lower on carbs, you'll probably feel it in your brain.

Her bigger point is balance. She agrees with the common advice to focus on protein first, but she stresses that you still need enough carbohydrates and enough fat. Without them, she says, you can end up short on energy in ways your body will rebel against, both in the activities you're doing and in the results you're after.

So if every low-carb attempt has left you foggy and dragging, that's not a personal failing. It's a plan that leaves your brain short on the fuel it prefers. Building in moderate, balanced carbs alongside your protein and fat is the approach the show recommends.