To-Do List App with Sync, Repeating To-Dos for daily food tracking
Check the out "Things". Things is a great to-do app that has cloud sync, repeating to-dos, and notes. For organization, a "to-do item" can be tagged, placed in a project (like a folder), or in an Area Of Responsibility (like a tag). Things is very flexible and would probably work for your diet plan. 

You can try the app for free, but the Mac version is $49.99, and iPhone version is $9.99. Unfortunately, there is no web-app.

https://culturedcode.com/things/