<ul class="nav">
    <li class="active controls_menu">
      <a href="content_pizza.php" id="" class="change-content">
        <i class="glyphicon glyphicon-th-list"></i>Tabela de Pizzas </a>
    </li >
    <li class ="controls_menu">
      <a href="thumbls_pizza.php" id="" class="change-content">
        <i class="glyphicon glyphicon-picture"></i>Ver todas Pizzas </a>
   </li>

$(document).ready(function() {
    $("#apresenta_pizza").load("content_pizza.php");
    $('.change-content').click(function() {
        $("#apresenta_pizza").load($(this).attr('href'));
        return false;
    });
});