diff --git a/examples/fitness/lib/main.dart b/examples/fitness/lib/main.dart
index 7dda3cd90df..8881905597e 100644
--- a/examples/fitness/lib/main.dart
+++ b/examples/fitness/lib/main.dart
@@ -20,15 +20,20 @@ part 'meal.dart';
 part 'measurement.dart';
 part 'settings.dart';
 
-class UserData {
-  UserData();
+abstract class UserData {
+  BackupMode get backupMode;
+  List<FitnessItem> get items;
+}
+
+class UserDataImpl extends UserData {
+  UserDataImpl();
 
   List<FitnessItem> _items = [];
 
-  BackupMode _backupSetting;
-  BackupMode get backupSetting => _backupSetting;
+  BackupMode _backupMode;
+  BackupMode get backupMode => _backupMode;
   void setBackupModeAndSave(BackupMode value) {
-    _backupSetting = value;
+    _backupMode = value;
     save();
   }
 
@@ -56,12 +61,12 @@ class UserData {
 
   Future save() => saveFitnessData(this);
 
-  UserData.fromJson(Map json) {
+  UserDataImpl.fromJson(Map json) {
     json['items'].forEach((item) {
       _items.add(new Measurement.fromJson(item));
     });
     try {
-      _backupSetting = BackupMode.values.firstWhere((BackupMode mode) {
+      _backupMode = BackupMode.values.firstWhere((BackupMode mode) {
         return mode.toString() == json['backupMode'];
       });
     } catch(e) {
@@ -72,14 +77,14 @@ class UserData {
   Map toJson() {
     Map json = new Map();
     json['items'] = _items.map((item) => item.toJson()).toList();
-    json['backupMode'] = _backupSetting.toString();
+    json['backupMode'] = _backupMode.toString();
     return json;
   }
 }
 
 class FitnessApp extends App {
   NavigationState _navigationState;
-  UserData _userData = new UserData();
+  UserDataImpl _userData = new UserDataImpl();
 
   void didMount() {
     super.didMount();
@@ -88,10 +93,6 @@ class FitnessApp extends App {
     }).catchError((e) => print("Failed to load data: $e"));
   }
 
-  void save() {
-    _userData.save().catchError((e) => print("Failed to load data: $e"));
-  }
-
   void initState() {
     _navigationState = new NavigationState([
       new Route(
@@ -120,9 +121,9 @@ class FitnessApp extends App {
       new Route(
         name: '/settings',
         builder: (navigator, route) => new SettingsFragment(
-          navigator,
-          _userData.backupSetting,
-          settingsUpdater
+          navigator: navigator,
+          userData: _userData as UserData,
+          updater: settingsUpdater
         )
       ),
     ]);
diff --git a/examples/fitness/lib/settings.dart b/examples/fitness/lib/settings.dart
index b7a1724fe1a..39f81d9dfc9 100644
--- a/examples/fitness/lib/settings.dart
+++ b/examples/fitness/lib/settings.dart
@@ -10,10 +10,10 @@ typedef void SettingsUpdater({
 
 class SettingsFragment extends Component {
 
-  SettingsFragment(this.navigator, this.backup, this.updater);
+  SettingsFragment({ this.navigator, this.userData, this.updater });
 
   final Navigator navigator;
-  final BackupMode backup;
+  final UserData userData;
   final SettingsUpdater updater;
 
   void _handleBackupChanged(bool value) {
@@ -38,10 +38,10 @@ class SettingsFragment extends Component {
           padding: const EdgeDims.symmetric(vertical: 20.0),
           child: new Block([
             new DrawerItem(
-              onPressed: () { _handleBackupChanged(!(backup == BackupMode.enabled)); },
+              onPressed: () { _handleBackupChanged(!(userData.backupMode == BackupMode.enabled)); },
               children: [
                 new Flexible(child: new Text('Back up data to the cloud')),
-                new Switch(value: backup == BackupMode.enabled, onChanged: _handleBackupChanged)
+                new Switch(value: userData.backupMode == BackupMode.enabled, onChanged: _handleBackupChanged)
               ]
             )
           ])
diff --git a/examples/fitness/lib/user_data.dart b/examples/fitness/lib/user_data.dart
index c182e6fc186..d6f0a3c213a 100644
--- a/examples/fitness/lib/user_data.dart
+++ b/examples/fitness/lib/user_data.dart
@@ -26,11 +26,11 @@ Future<UserData> loadFitnessData() async {
   print("Loading from $dataPath");
   JsonDecoder decoder = new JsonDecoder();
   Map data = await decoder.convert(await new File(dataPath).readAsString());
-  return new UserData.fromJson(data);
+  return new UserDataImpl.fromJson(data);
 }
 
 // Intentionally synchronous for execution just before shutdown.
-Future saveFitnessData(UserData data) async {
+Future saveFitnessData(UserDataImpl data) async {
   String dataPath = await dataFilePath();
   print("Saving to $dataPath");
   JsonEncoder encoder = new JsonEncoder();