Today’s prompt, and the companion piece behind it.
The Fasting Stages
What physical sensations typically occur at different stages of a 24-hour fast?
The Short Answer
Fasting produces predictable stages: initial hunger (hours 0-4) that often fades, a stable period (hours 4-16) as the body shifts fuel sources, possible increased hunger around typical meal times, and a widely described sense of clarity and energy (hours 16-24) as ketone production rises, reported rather than demonstrated. The key insight is that hunger comes in waves rather than building continuously: waiting out a wave often brings relief rather than escalating discomfort.
Something to Sit With
Hunger isn’t a steadily climbing emergency. It rises, peaks, and falls, even if you don’t eat.
Knowing this changes how you respond to it.
Learn More
The early hours (0-4). What you feel depends heavily on when you last ate and what it was.
If your last meal was carbohydrate-heavy: Blood sugar drops as insulin clears the glucose. You may feel hungry, irritable, or low-energy as the body transitions.
If your last meal was protein and fat: The transition is often smoother. Satiety signals persist longer.
During this phase, the body is still running primarily on glucose from the recent meal and liver glycogen. You’re not truly fasting metabolically yet: you’re digesting.
The transition (4-8 hours). Digestion completes. Blood glucose stabilizes. The liver begins releasing glycogen to maintain blood sugar.
Hunger may be present but often isn’t urgent. The body has resources to draw on. Many people feel normal during this period: this is why time-restricted eating (skipping breakfast, eating in an 8-hour window) is sustainable for most.
The meal-time waves (variable). Hunger often spikes around times you normally eat. This is hormonal: ghrelin (the hunger hormone) is released on schedule, possibly shaped by habit. Not entirely: ghrelin also rises before meals people begin unprompted, with no clock or cue; the signal is real, whatever part habit plays in its timing.[1]
The key insight: these spikes pass. Ghrelin rises, peaks, and falls, even without food.[1] If you wait out the wave, the hunger typically subsides without eating.
This pattern, hunger as waves rather than a continuous climb, is what makes fasting sustainable. You’re not fighting constantly increasing discomfort; you’re riding out temporary surges.
The shift (from about 12 hours). Glycogen stores begin depleting. The body increasingly mobilizes fat for fuel. Ketone production begins, and the full switch is usually placed anywhere from 12 to 36 hours in.[2]
Many people report a second wind during this period. Mental clarity may improve as ketones become available to the brain. Physical energy often stabilizes or increases.
Hunger may still occur but often feels less urgent. The body has found its alternative fuel source.
The established fast (16-24 hours). By this point, you’re running significantly on fat. Ketone levels are measurable. Growth hormone has risen by the 24-hour mark, the earliest point anyone measured it.[3] Autophagy (cellular cleanup) may be beginning.[2]
Physical sensations vary:
Energy. Often stable or elevated. Some people feel more alert and focused than when fed.
Hunger. Typically mild or absent. The waves continue but may be less frequent.
Physical lightness. Many report feeling unburdened, clear, energetic.
Cold. Some people feel cooler as the body conserves energy.
What to expect with practice. The sensations change over time:
First fasts: The hunger waves may feel intense. The transition can be uncomfortable. This is unfamiliar territory.
With experience: The body adapts. Hunger becomes gentler. The transition smooths out. You learn to recognize and ride the waves.
Fat adaptation (training the body to efficiently burn fat) is a low-carbohydrate training book’s account rather than a measured finding, and what it describes is athletes’ fuel use, not how a fast feels.[4] Whether fasting itself gets easier with practice is a common report that nobody has followed anyone across repeated fasts to check.
Further reading:
- Fung J & Moore J, The Complete Guide to Fasting[5] (2016) — Practical guide to fasting stages
- Anton SD et al., “Flipping the metabolic switch: understanding and applying health benefits of fasting”[6] — Obesity, 2018
- de Cabo R & Mattson MP, “Effects of intermittent fasting on health, aging, and disease”[7] — New England Journal of Medicine, 2019
- Cummings DE et al., “A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans”[8] — Diabetes, 2001
Written by AI, directed and approved by me. How this is made →
You already know what to eat
You already know enough.
The information isn’t the problem. You have plenty of information.
The problem is that by the time you’re standing in front of the fridge — tired, negotiating with yourself about whether you’ve earned a snack — it’s already too late. Your habits have voted. Willpower shows up late, outnumbered.
So what if the right thought arrived before all of that?
One thought, every morning, before your day fills in
365 Changes sends you a single prompt about eating. It arrives early — before hunger, before decisions, before habits kick in.
Not a meal plan. Not a rule. Just a question or idea to sit with while you make coffee. Each is simple, but they accumulate.
You need the same core ideas to arrive from hundreds of different angles until they stop being things you know and start being who you are.
Get the daily prompt free:
Here’s what a prompt looks like
Each morning you’ll get a question or scenario like:
You’re in a bad mood and craving comfort food. What do you do first?
Click any of these and read the response. Each one is a complete thought worth reading on its own. The daily email makes sure one arrives before you need it.
- What physical sensations typically occur at different stages of a 24-hour fast?
- What happens to growth hormone, adrenaline, and metabolic rate during a 24-36 hour fast?
- Your expectations are unrealistic and you’re constantly disappointed. What expectations need adjusting?
Why daily? Why morning? Why small?
Daily, because change doesn’t happen in one big moment of clarity. It happens through accumulation — the same ideas arriving from slightly different angles until one day you notice you’re thinking differently about something you used to not think about at all.
Morning, because evenings are when you negotiate. Mornings are when you can still hear yourself think. There’s a small window before the momentum builds, before the habits wake up. That’s when a thought can land.
Small, because you’ve already heard it all. You don’t need another article, another tip, another list. You need the right ideas to keep showing up until they stick.
This is not a diet program
There’s no tracking. No streaks. No badges. No notifications begging for attention.
If you open the email, good. If you don’t, it doesn’t guilt you. There’s no streak to break. Tomorrow another one arrives.
One email. It asks almost nothing. It just shows up.
Free. No tracking. No streaks. Just one email, every morning.
Does it work?
Honestly? We don’t know if it will work for you.
I built this for myself. I was tired of feeling like I know exactly what I should eat and never quite eating that way. Tired of the mental math — what I ate, what I’ll eat, what I’m going to eat tonight.
I didn’t need more information. I needed the right thought to arrive at the right time. So I built something that does that, every morning, and I started using it.
It’s working. Slowly. I can’t point to a moment when things changed. I just notice that they have.
—Craig
How this gets made is written down too.
The writing here is done by AI. I direct it, and I approve everything before it publishes. Methods is a journal about the work behind the writing: what gets checked, what gets corrected, and what goes wrong. Methods is free, public, and nothing you have to read.
One way to find out:
Want more depth?
Some mornings the prompt will make you curious. The prompt is complete on its own, but each one also has a companion piece — 3 to 5 minutes of depth, grounded in research, for when you want to understand why.
All 500 companions are free to read. Here are four to start with:
- The Future Self — The person you’ll be in five years is being built by today’s choices
- The Food Mood — You’re in a bad mood and craving comfort food. What do you do first?
- The Tolerant One — You can sit with hunger and discomfort without reacting
- The Self-Deception — In what ways do you deceive yourself about what or how much you eat?
The daily email carries each prompt with its full companion. Subscribe below and it comes to you every morning.