What are the healthiest cooking methods for preparing meals?

Steaming - cooking food by exposing retains nutrients and flavor.
Boiling - A healthy cooking method but boiling for too long causes the loss of some nutrients.
Grilling - cooking food over an open flame allows surplus fat to drip from the food.
Baking and roasting - involve cooking in an oven, which can retain nutrients and flavors.
Stir-frying - A healthy method of cooking food in high heat.
Poaching - involves cooking food in liquid at a low temperature.
The healthiest cooking methods involve minimal added fats, salt, and sugar.