There is. I use both myself. MFP and Fitbit can be linked together. Basically this is how you should do it:
1) Have both Fitbit and MFP apps on your phone.
2) Sync your actiivity via the Fitbit app.
3) Record your food intake via the MFP app.
When both MFP and Fitbit are linked, Fitbit will send the data to MFP, which will register it as a "Fitbit Calorie Adjustment" under Exercise. As the day goes on, the Exercise calories under MFP will change based on this adjustment. If you're syncing your tracker throughout the day (which is easily done via the phone app), make sure to enable Negative Calorie Adjustments in the MFP settings. This takes full advantage of syncing via the app, as syncing throughout the day will give greater accuracy as to how many calories left you "really" have under your MFP plan.
Just remember that the calorie burn under MFP will not exactly match that on your dashboard or tracker. This is because MFP tweaks it based on its calorie burn projections compared to Fitbit's projections. Also note that at the beginning of the day the adjustment may either be zero, or in the negative (if negative calorie adjustment is enabled). This is because you haven't registered a lot of activity yet. Don't worry, the number will improve through the day.
Take a look at the following links on Fitbit and MFP's pages. Especially look at the MFP page (scroll down a bit to the "Fitbit Tracker Integration" section with the Q&A) as it has important information on how to use MFP while integrated.
http://www.myfitnesspal.com/help/section/65-fitbit-tracker-integration
edit: I can spell, really!
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