Trendy diets come and go, but intermittent fasting (IF) has proven popular and shows promising results in scientific studies. But while the basic concept is simple (restrict your eating to certain hours or days and fast occasionally in between), it can be tricky in practice.

You’ll need to choose a specific IF cadence (there’s 16:8, 5:2, alternating fasting, and others), use schedules or timers, and develop the willpower not to break your fast. Not surprisingly, there are some excellent apps that can help. Here are the best IF apps for iOS and Android.

Zero is a very polished and easy to use fasting app. It starts by assessing your goals and what kind of eating plan you are currently on, and then matches you with a plan that is not all that different.

The app can send you notifications when it’s time to start or stop fasting. It also lets you easily track your progress over time. For example, you can celebrate your fasting periods and see how your weight changes over time.