Category: Forum

The Fasting-Mimicking Diet (FMD) was developed by Valter Longo, director of the Longevity Institute at USC, through decades of research on caloric restriction, autophagy, and stem cell regeneration.

The key insight from Longo’s lab was that it’s not zero calories that matter — it’s the absence of signals that tell the body nutrients are available (primarily protein and sugar). With the right macro composition (very low protein, very low sugar, higher healthy fat), the body enters a fasting-like state even with some caloric intake.

The FMD human protocol is typically 700–1,100 kcal daily calorie intake.

Valter Longo describes FMD in his book The Longevity Diet: Discover the New Science Behind Stem Cell Activation and Regeneration to Slow Aging, Fight Disease, and Optimize Weight. The FMD research — including the comparison to water fasting effects — is described primarily in Chapters 6 and 7, where Longo walks through the clinical trials and the mechanistic reasoning behind why caloric restriction with the right macros mimics prolonged fasting at the cellular level.

The landmark peer-reviewed paper behind the book:
Brandhorst S. et al., “A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan,” Cell Metabolism, 2015.

How the app uses FMD: the app includes a toggle to track time spent within a fast-mimicking window. This is informational only — unlike dry fasting, enabling FMD doesn’t change your effective fast hours. Use the FMD toggle if you’ve consumed some calories but believe you’re still within FMD constraints (under 800–1,100 kcal depending on the day, with macronutrients consistent with the FMD protocol).

During a dry fast, you consume nothing at all — no food and no liquids. This is unlike a water fast, where you avoid calories but can drink freely: water, black coffee, unsweetened tea.

By some measures, 1 day of dry fasting delivers the same metabolic benefit as 3 days of water fasting.

The effect varies between individuals — so the app includes an adjustable multiplier specifically for dry fasts. If you’ve observed or believe that dry fasting is 3× more effective than water fasting for you, set the multiplier to 3.

As an example, the app’s author has observed that his muscle mass loss is 2.6 times lower during dry fasts compared to water fasts. Since muscle preservation is his most important metric, he sets the multiplier at 2.6.

By empirical observation, in everyday situations without intense cardio, a dry fast feels about the same as a water fast — but with amplified effects, which include:

• Preserving muscle mass better (roughly 2× less muscle loss during dry fasts)
• Increased immune response, as dry fasting helps eliminate harmful bacteria
• Accelerated fat burn, since the body must burn fat not only for energy but also to produce the water it needs for biological processes

The app includes a toggle to track dry fasting, including when it’s part of a longer fast that combines both dry and water phases.

A. Getting started

1. Choose your intended fast length in hours (or days and hours), press Start, and you’re fasting.
2. Once the fast is running:
   • The progress bar tracks your fast against your intended hours. Its colour shifts from grey to yellow to green as you progress — each colour tied to the metabolic state your body is entering.
   • A status message below the bar briefly describes what’s happening in your body at that stage.
   • A summary line shows the percentage of intended time elapsed and the projected completion time.
3. Dry fasting: if you plan to go without any liquids for longer than 12 hours — even as part of a longer water fast — enable Dry Fast in Settings and flip the toggle when you begin. You can adjust the dry-to-water fast multiplier or leave it at the default of 3 (meaning 1 day of dry fasting is treated as equivalent to 3 days of water fasting). The app recalculates your effective fast hours accordingly.
4. Fast-mimicking mode: if you eat something during a fast — intentionally or by accident — but your intake stays under 500 kcal in any 24-hour window, toggle on Fast-Mimicking mode instead of ending the fast. This doesn’t change your effective fast hours; it adds a visual marker to the progress bar so you can see when you were in a fast-mimicking window.

How dry fasting shows on the progress bar: dry fast time appears as a black dotted line for the first 12 hours. If you stop the dry fast before 12 hours, the dotted line stays as a visual marker but doesn’t affect your effective hours. Once you pass 12 hours, the line turns solid and the app multiplies those hours by your multiplier to calculate effective fast time. Example: 16 hours of dry fasting × 3 (default multiplier) = 48 effective fast hours.

B. Notes and mood log

During a fast, you can log your mood on a 1–10 scale. Press Save and the rating appears directly on the progress bar, giving you a visual map of how you felt over the course of the fast.

You can also add timestamped notes at any point. These become valuable when you review past fasts — patterns emerge, and you learn what works for your body. Notes and photos are included when you export your data, making them especially useful if you run your fasting history through an AI tool for analysis.

The free version includes mood logs and text notes. Premium adds photo attachments — snap a photo or pick one from your library.

C. Data export

Your data stays on your device — the app doesn’t store anything externally. Whenever you want, go to Settings → Export Data and everything is saved as a .json file.

JSON is readable by a wide range of apps and is ideal for AI analysis, either on its own or combined with data from smart scales, rings, or watches.

Most fasting apps count down to a finish line. This one doesn’t — and that’s by design.

Paleo Fasting was shaped by people who fast regularly, not by people who read about fasting. All the essentials are here — timer, mood log, notes — free, for everyone, permanently. But a few things work differently than you might expect.

No countdown to “done”

You won’t find a timer counting down to zero. You set intended fast hours — and that’s a deliberate, philosophical choice.

Fasting is not something you should do. It’s something you choose to do. No meaningful experience deserves a deadline ticking over your head. Your body is not a stopwatch; it doesn’t operate on a precise hour-by-hour schedule, and neither should your mindset.

Here’s what that means in practice: if you set out to fast 72 hours but stop at 48 — or even at 16 — this app records that as a success. Because it is one. Life intervenes, your body sends signals, plans change. A shorter fast is still a fast. The app will never brand any session a “failure,” regardless of what you originally intended.

Intended hours, not a hard goal. You’re always welcome to hit them or go beyond — but you’ll never be punished for listening to your body.

Dry fasting mode

Dry fasting — no food and no liquids — is water fasting with the intensity turned up. The research is still young, but what exists is compelling: dry fasting may deliver roughly 3× the metabolic benefit of a water fast over the same period. Muscle preservation appears to be about 2× better, while fat loss and autophagy accelerate.

The app lets you track dry fasting segments within a longer fast and adjust a personal multiplier based on your own observations. There’s a dedicated forum post on the science and practicalities — worth reading before you try it.Fast-mimicking mode

Fast-mimicking mode

You’re mid-fast and you eat something. Fast ruined? Not necessarily. Research led by Valter Longo at USC shows that fasting benefits remain largely intact when daily intake stays between 800 and 1,100 kcal with the right macro profile — very low protein, very low sugar, moderate healthy fat.

The app includes a toggle for this: flip it on and your progress bar reflects that you’ve entered a fast-mimicking window rather than broken the fast entirely. More on how this works and the research behind it in a separate forum post.