function my_bp_activities_include_activity_types( $retval ) {
    // only allow the following activity types to be shown
    $retval['action'] = array(
        'activity_update',
        'activity_comment',
        'new_blog_post',
        'new_blog_comment',
        'friendship_created',
        'created_group',
    );

    return $retval;
}
add_filter( 'bp_after_has_activities_parse_args', 'my_bp_activities_include_activity_types' );