Fitbit-Rate-Limit-Remaining:

[1] Fitbit Web API Basics — Fitbit Web API Docs (2016-10-05 06:00:11 +09:00) <https://dev.fitbit.com/docs/basics/>

Response Headers
Fitbit API responses include headers that provide you with your rate limit status.
Fitbit-Rate-Limit-Limit: The quota number of calls.
Fitbit-Rate-Limit-Remaining: The number of calls remaining before hitting the rate limit.
Fitbit-Rate-Limit-Reset: The number of seconds until the rate limit resets.