<?php

global $wpdb;

$updates = $wpdb->get_results( "SELECT * FROM {$wpdb->usermeta} WHERE meta_key = 'bp_latest_update' AND meta_value != ''" );

foreach ( $updates as $update ) {
	$unserialized = maybe_unserialize( $update->meta_value );
	if ( ! is_object( $unserialized ) ) {
		continue;
	}

	$array = (array) $unserialized;

	bp_update_user_meta( $update->user_id, 'bp_latest_update', $array );
}