Combining multiple custom fields into single query?

I have a series of 3 custom fields that I am calling for each post. On pages where I have 10+ posts displaying, it is adding a lot of extra database queries. I’m hoping there is some way to combine the 3 queries into a single one, to hopefully reduce the load on the server. Here is what I have now, within the post loop so the 3 fields show conditionally on each post (must be conditional because the span shouldn’t display at all if the field is empty):

<?php
$cat1 = get_post_meta($post->ID, 'level', true);
if ( $cat1 ) {
 echo '<span class="cat1">';
 echo $cat1;
 echo '</span>';
}
?>
<?php
$cat2 = get_post_meta($post->ID, 'time', true);
if ( $cat2 ) {
 echo '<span class="cat2">';
 echo $cat2;
 echo '</span>';
}
?>
<?php
$cat3 = get_post_meta($post->ID, 'cat', true);
if ( $cat3 ) {
 echo '<span class="cat3">';
 echo $cat3;
 echo '</span>';
}
?>

Any ideas for how to make this more efficient?