Whether you own a Fitbit device or not, you can still use the free MyFitnessPal app that I usually use. On my first use, I had to manually enter several foods that could not be found in the Fitbit database. If you want to count calories for the purpose of losing weight though, Fitbit makes it easy to select a goal based on your desired weight loss.
You can also track your calorie burn via exercise, but the search function for this is very basic. You have to input what you were doing and see if it comes up in the database. At least with other apps, you get to pick between strength and cardio. I found this very unhelpful since I tend to do mostly fitness classes and not straight-up cardio. This healthy app also has a helpful water-tracking function so you can make sure you are well hydrated.
Overall, if you are already using the Fitbit device to track your steps every day, you have nothing to lose my using the Android app. If you are not a Fitbit user, I would steer clear of this app and check out some of the more comprehensive nutrition apps available. At least until they upgrade Fitbit a bit more.