There are plenty of features I use that are not part of the app that I always have one browser window open to SP on my phone and PC. I find it easier to read articles and emailed links, create blog posts and what not.
You can create the food groups on the web site and they will then appear as choices on the phone app.
We talk about the app here, but SP doesn't necessarily monitor this team, so we usually recommend putting an entry in the 'Site/Technical Help' forum. Click the Community tab above and you'll see that forum listed. User feedback drove getting 'spin the wheel' and reading articles into the app. Many others have asked about food grouping via the app so it would be worth it to share your request, too. Maybe that will be part of the next software release!
Those who think they have no time for a healthy lifestyle will sooner or later will have to find time for illness.