On Fast

An intermittent fasting smartwatch app


UX/UI Designer


November to December 2022




In recent years, intermittent fasting has gained popularity. As a result, many use applications to track fasting hours efficiently. However, existing apps often need more features and flexibility to help users stay motivated. This project aims to design a smartwatch fasting tracker that provides solutions for current gaps in the market. The goal is to design an app that is simple, intuitive, and user-friendly.

What is Intermittent Fasting?

Intermittent fasting is a dietary pattern of alternating eating and fasting periods. Researchers believe it can lead to weight loss, improve insulin sensitivity, decrease inflammation, and even increase lifespan. There are several methods to practice intermittent fasting. The most common schedule is the 16:8 period, where fasting is done for 16 hours and eating for 8. On the other hand, examples of more aggressive fasts include 20:4 or 23:1.

Since practicing intermittent fasting requires specific eating and fasting periods, users often utilize tracking applications to ensure success in following this dietary practice.

User Research

As an intermittent fasting practitioner, I have tried several tracking applications and observed their pros and cons. However, to fully understand the unaddressed problems in the market, I interviewed 3 of my family members who use a smartwatch to track their fastings and discussed their experience with fasting trackers.

Based on our discussions, I gathered the top 3 issues they encounter while using current applications:

Problem Statement

Intermittent fasting practitioners who use a smartwatch to track fasting periods need to accurately track their fasting hours to succeed on the intermittent fasting diet.

Hypothesis Statement

If intermittent fasting practitioners who use a smartwatch download an app that offers plan flexibility, then they can adjust their fasting hours to better suit their lifestyles.

On Fast App Value Proposition

I analyzed the gathered information from talking to users to come up with valuable features that will make On Fast stand out in the market.



Usability Test

I tested the prototype with the same user group from my research. I then asked them to follow three prompts to assess the usability of the app.

Prompt 1: Create a custom fast
Prompt 2: Start and stop fasting timer
Prompt 3: Edit fasting plan


3/3 successfully completed Prompt 1
2/3 successfully completed Prompt 2
Failure reason: User was not able to confirm an action to start or end a fast.
2/3 successfully completed Prompt 3
Failure reason: User was not able to edit a preferred fasting plan.

Updated Designs

Updated Prototype


If given more time, I would like to conduct a second round of usability study to update the app further and improve its features.
Overall, I am pleased with the result of this project. In addition, this project showed how I could utilize a small canvas to provide a product that is effective and visually pleasing. Since there is also such a small space to work with, I learned how to use creative solutions to deliver a purposeful and valuable design for the users.