diff --git a/backend/app/api/garmin_sync.py b/backend/app/api/garmin_sync.py
index 84345d2..e7cee88 100644
--- a/backend/app/api/garmin_sync.py
+++ b/backend/app/api/garmin_sync.py
@@ -18,6 +18,7 @@ class GarminConfigIn(BaseModel):
     sync_enabled: bool = True
     sync_activities: bool = True
     sync_wellness: bool = True
+    sync_lookback_days: int = 30         # days to look back on first sync; -1 = all-time
 
 
 class GarminConfigOut(BaseModel):
@@ -25,9 +26,10 @@ class GarminConfigOut(BaseModel):
     sync_enabled: bool
     sync_activities: bool
     sync_wellness: bool
+    sync_lookback_days: int
     last_sync_at: Optional[datetime]
     last_sync_status: Optional[str]
-    connected: bool                       # True when credentials exist
+    connected: bool
 
     class Config:
         from_attributes = True
@@ -45,14 +47,15 @@ async def get_config(
     if not cfg:
         return GarminConfigOut(
             email="", sync_enabled=False, sync_activities=True,
-            sync_wellness=True, last_sync_at=None, last_sync_status=None,
-            connected=False,
+            sync_wellness=True, sync_lookback_days=30,
+            last_sync_at=None, last_sync_status=None, connected=False,
         )
     return GarminConfigOut(
         email=cfg.email,
         sync_enabled=cfg.sync_enabled,
         sync_activities=cfg.sync_activities,
         sync_wellness=cfg.sync_wellness,
+        sync_lookback_days=cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30,
         last_sync_at=cfg.last_sync_at,
         last_sync_status=cfg.last_sync_status,
         connected=True,
@@ -92,6 +95,7 @@ async def save_config(
         cfg.sync_enabled = body.sync_enabled
         cfg.sync_activities = body.sync_activities
         cfg.sync_wellness = body.sync_wellness
+        cfg.sync_lookback_days = body.sync_lookback_days
         cfg.last_sync_status = "Credentials updated"
     else:
         cfg = GarminConnectConfig(
@@ -102,6 +106,7 @@ async def save_config(
             sync_enabled=body.sync_enabled,
             sync_activities=body.sync_activities,
             sync_wellness=body.sync_wellness,
+            sync_lookback_days=body.sync_lookback_days,
             last_sync_status="Connected",
         )
         db.add(cfg)
@@ -114,6 +119,7 @@ async def save_config(
         sync_enabled=cfg.sync_enabled,
         sync_activities=cfg.sync_activities,
         sync_wellness=cfg.sync_wellness,
+        sync_lookback_days=cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30,
         last_sync_at=cfg.last_sync_at,
         last_sync_status=cfg.last_sync_status,
         connected=True,
diff --git a/backend/app/services/garmin_connect_sync.py b/backend/app/services/garmin_connect_sync.py
index 04c3e05..5f6e009 100644
--- a/backend/app/services/garmin_connect_sync.py
+++ b/backend/app/services/garmin_connect_sync.py
@@ -67,12 +67,13 @@ def authenticate_garmin(email: str, password_enc: str, token_store: Optional[str
 # ── Activity sync ─────────────────────────────────────────────────────────────
 
 def sync_activities(garmin, user_id: int, since: Optional[datetime],
-                    db, file_store_path: str) -> int:
+                    db, file_store_path: str, lookback_days: int = 30) -> int:
     """
     List activities from Garmin Connect, skip any already in the DB, download
     FIT ZIPs for new ones, and queue them for processing.
 
-    On first sync (since=None) fetches the full account history back to 2010.
+    On first sync (since=None) the start date is determined by lookback_days:
+      -1 → full history back to 2010; N → today minus N days.
     On incremental syncs fetches from one day before last_sync_at.
     Returns the number of new activities queued.
     """
@@ -81,8 +82,12 @@ def sync_activities(garmin, user_id: int, since: Optional[datetime],
     from app.models.user import Activity
     from sqlalchemy import select, func
 
-    # First sync: fetch everything; incremental: one day overlap to catch late uploads
-    start_date = (since - timedelta(days=1)).date() if since else date(2010, 1, 1)
+    if since:
+        start_date = (since - timedelta(days=1)).date()
+    elif lookback_days == -1:
+        start_date = date(2010, 1, 1)
+    else:
+        start_date = date.today() - timedelta(days=max(lookback_days, 1))
     end_date = date.today()
 
     try:
diff --git a/backend/app/workers/tasks.py b/backend/app/workers/tasks.py
index da33b71..907df6d 100644
--- a/backend/app/workers/tasks.py
+++ b/backend/app/workers/tasks.py
@@ -499,7 +499,8 @@ def sync_garmin_connect_user(user_id: int):
         if cfg.sync_activities:
             try:
                 activities_queued = sync_activities(
-                    garmin, user_id, cfg.last_sync_at, db, settings.file_store_path
+                    garmin, user_id, cfg.last_sync_at, db, settings.file_store_path,
+                    lookback_days=cfg.sync_lookback_days if cfg.sync_lookback_days is not None else 30,
                 )
             except Exception as exc:
                 errors.append(f"activities: {exc}")
diff --git a/frontend/src/pages/ProfilePage.jsx b/frontend/src/pages/ProfilePage.jsx
index 43e0e20..d40e22f 100644
--- a/frontend/src/pages/ProfilePage.jsx
+++ b/frontend/src/pages/ProfilePage.jsx
@@ -115,7 +115,7 @@ export default function ProfilePage() {
     queryKey: ['garmin-config'],
     queryFn: () => api.get('/garmin-sync/config').then(r => r.data),
   })
-  const [gcForm, setGcForm] = useState({ email: '', password: '', sync_enabled: true, sync_activities: true, sync_wellness: true })
+  const [gcForm, setGcForm] = useState({ email: '', password: '', sync_enabled: true, sync_activities: true, sync_wellness: true, sync_lookback_days: 30 })
   const [gcSaved, setGcSaved] = useState(false)
   const [gcError, setGcError] = useState('')
   const [gcSyncing, setGcSyncing] = useState(false)
@@ -127,6 +127,7 @@ export default function ProfilePage() {
         sync_enabled: garminConfig.sync_enabled,
         sync_activities: garminConfig.sync_activities,
         sync_wellness: garminConfig.sync_wellness,
+        sync_lookback_days: garminConfig.sync_lookback_days ?? 30,
       }))
     }
   }, [garminConfig])
@@ -145,7 +146,7 @@ export default function ProfilePage() {
     mutationFn: () => api.delete('/garmin-sync/config'),
     onSuccess: () => {
       refetchGarmin()
-      setGcForm({ email: '', password: '', sync_enabled: true, sync_activities: true, sync_wellness: true })
+      setGcForm({ email: '', password: '', sync_enabled: true, sync_activities: true, sync_wellness: true, sync_lookback_days: 30 })
     },
   })
   const triggerGarminSync = async () => {
@@ -345,6 +346,14 @@ export default function ProfilePage() {
               </label>
             ))}
           </div>
+
+          <Field label="Sync lookback days" hint="-1 syncs all available history (back to 2010). Leave at 30 for incremental syncs.">
+            <Input type="number" value={gcForm.sync_lookback_days} min={-1}
+              onChange={e => setGcForm(f => ({ ...f, sync_lookback_days: parseInt(e.target.value, 10) || 30 }))} />
+            {gcForm.sync_lookback_days > 365 && gcForm.sync_lookback_days !== -1 && (
+              <p className="text-yellow-400 text-xs mt-1">Warning: syncing more than 365 days at once may take a long time and could trigger Garmin rate limits.</p>
+            )}
+          </Field>
         </div>
 
         {gcError && <p className="text-red-400 text-xs">{gcError}</p>}