Hi,

Have you ever noticed you think more clearly when you haven't eaten in a while? Not starving—just that window where everything feels a bit sharper.

I kept hearing people talk about this, so I went digging. Here's what's actually going on.

Your body runs on two fuels: sugar from food you recently ate, and fat you've stored. The catch—it always picks sugar first. Won't touch fat stores until the sugar runs out.

When you eat, blood sugar rises. Body releases insulin to handle it. Insulin moves sugar into cells for energy. Leftover sugar gets stored as fat. Here's the key part: while insulin is high, you're in storage mode. Adding fat, not burning it.

Most people eat constantly. Breakfast, lunch, dinner, snacks between. Insulin stays elevated most of the day. The body never gets the signal to switch over and burn stored fat.

What happens when you stop eating for a while

After about 12-16 hours without food, the body runs out of easy sugar. Now it has to use fat for energy instead. The liver breaks down fat into ketones, which the brain and muscles can use as fuel.

This is the fasted state. Most people never reach it because they eat something before the switch happens.

What intermittent fasting does

Intermittent fasting usually means eating within an 8-hour window and not eating for 16 hours. Noon to 8pm, then nothing until noon the next day.

This guarantees you hit that switch point every day. Real time burning fat instead of just storing it.

Three things that happen when you fast regularly

One: your body gets better at responding to insulin. When insulin is constantly high, cells start ignoring it. That's insulin resistance—leads to problems like diabetes. Fasting gives cells a break, keeps them sensitive.

Two: you burn stored fat. Not because you're starving yourself, but because the body finally gets the chance to access what it's been saving.

Three: cells clean themselves. There's a process called autophagy where cells break down damaged parts and recycle them. Only happens when you're not constantly digesting. Think of it like your room—can't clean it while you're still making a mess. You need to stop first.

Does timing actually matter?

Some people say fasting is just about eating less. Fewer calories, lose weight. Done.

But that's not the whole picture. Two people eat the same amount of food—one eats over 14 hours, the other within 8 hours. Their bodies respond differently. Shorter eating window means more time with low insulin, more fat burning, more time for cellular cleanup. Same calories, different results.

That part surprised me when I first came across it.

Why fasting doesn't make you foggy

You'd think skipping meals would tank your focus. Often the opposite happens. The brain runs well on ketones.

Evolutionarily, this makes sense. Early humans couldn't afford to think clearly only when food was around. They needed sharp minds to find food when it was scarce.

The simple takeaway

Eating all day keeps you stuck in one mode: burn sugar, store fat, never clean up. Taking a break—16 hours or so—lets the body shift gears: burn fat, repair cells, reset.

It's not about eating less. It's about giving your body enough time to do maintenance. Like letting your phone battery drain before recharging, or closing apps so your computer runs faster.

Your body has a second gear. Most people never use it because they never stop eating long enough to shift into it.

Let me know if this matches what you've experienced.

Speak soon,

— York