Good interactional diet apps for iPhone?

I'm looking for an app that you can interact with others on? Like diet together with people from anywhere and everywhere, post pictures, messages and track progress? Was wondering if anyone knew any good apps that do this?

MyFitnessPal
It's free and you have the option to interact with people. It has helped me lose weight. There's the option to pay for extra services, but I think the extra options will benefit people with specific needs.