diff --git a/homeassistant/components/sensor/fitbit.py b/homeassistant/components/sensor/fitbit.py
index 01c067a19f2..eb87527a546 100644
--- a/homeassistant/components/sensor/fitbit.py
+++ b/homeassistant/components/sensor/fitbit.py
@@ -232,6 +232,11 @@ def setup_platform(hass, config, add_devices, discovery_info=None):
             authd_client.client.refresh_token()
 
         authd_client.system = authd_client.user_profile_get()["user"]["locale"]
+        if authd_client.system != 'en_GB':
+            if hass.config.units.is_metric:
+                authd_client.system = "metric"
+            else:
+                authd_client.system = "en_US"
 
         dev = []
         for resource in config.get("monitored_resources",