Save a product from the frontend

code.php

<?php
// save the old id
$oldStoreId = Mage::app()->getStore()->getId();
// set the store to be admin
Mage::app()->getStore()->setId(Mage_Core_Model_App::ADMIN_STORE_ID);
// set the orig data
$product->setOrigData();
// save the product
$product->save();
// reset the store id
Mage::app()->getStore()->setId($oldStoreId);