# Fast AI vs Flex3

The clearest difference is in-app purchases: Flex3 at none against Fast AI's 5. Flex3 also leads on iOS requirement (12.0 vs 14.0). Fast AI's advantage is update cadence (every 2 weeks vs every 5 weeks). On price, ads and device support there is nothing between them.

Both are free to download. Fast AI sells 5 in-app purchases, starting at $5.99 per 7 days. Flex3 asks for nothing beyond the download.

Fast AI ships an update every 2 weeks, Flex3 every 5 weeks. The most recent releases landed on October 20, 2026 and May 28, 2026 respectively.

## The numbers

| Metric | Fast AI | Flex3 |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.3 (120 ratings)](https://appshunter.io/ios/app/fast-ai-intermittent-fasting/id1629661646/reviews)** | — |
| Number of ratings | **120** | — |
| Positive reviews | 7.1% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 2 weeks** | Every 5 weeks |
| Monetization | Free with in-app purchases | — |
| Size | 101 MB | 29 MB |
| Requires iOS | 14.0 | **12.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 17+ |
| Developer | [Kiryl Salavei](https://appshunter.io/developer/1033680093) | [Aravind Athreya](https://appshunter.io/developer/1552166670) |

## What reviewers say

### Fast AI

[App page](https://appshunter.io/ios/app/fast-ai-intermittent-fasting/id1629661646)

This app helps users achieve weight loss and improve well-being through intermittent fasting. It provides tracking, scheduling, and detailed analytics to guide users through various fasting plans. The app aims to make fasting a natural and effective part of a healthy lifestyle.

**Highlights:** Intermittent fasting tracker, Weight monitoring, Fasting and food window notifications, Detailed analytics, Multiple fasting schemes (e.g., 16/8), Fasting schedule, Apple Health weight sync

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (5)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Simple intermittent fasting | $5.99 | per 7 days |
| Intermittent Fasting 1 Month | $12.99 | per month |
| Personal Fast Program 3 Month | $19.99 | per 3 months |
| Intermittent Fasting + Tracker | $35.99 | per year |
| Intermittent Fasting Annual | $49.99 | per year |


### Flex3

[App page](https://appshunter.io/ios/app/flex3/id6459503860)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Fast AI free?

Fast AI is free to download, with in-app purchases available.

### Is Flex3 free?

Flex3 is free to download, with no in-app purchases.

### Do Fast AI or Flex3 have ads?

Neither Fast AI nor Flex3 shows ads.

### Which is updated more often, Fast AI or Flex3?

Fast AI ships an update every 2 weeks, and Flex3 every 5 weeks. Most recently, Fast AI was updated on October 20, 2026 and Flex3 on May 28, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*