Stick to techniques that can be executed while emaciated.

There are many methods of martial arts which require or focus on the generation of great physical power. It has been my experience however that chances are you will have to defend yourself most often when you are at your weakest point physically, for this reason a great deal of time should be spent training in a way in which you use the minimal amount of energy necessary to manage a physical, mental, or spiritual conflict. This demands SKILL. The attack hardly ever comes when you are at your best. How would your method of training serve you while weak and vulnerable?
This is not taking into account the ability to channel internal power which is a different matter.