Well, I suspect that with karate you are often going extremely anerobic for short periods of time while the other activities allow you to stay within your aerobic range for a much greater period of time.

As to the karate, take a look into the Body Opus/CKD threads. You will hear about TKD (NO...not Tai Kwan Do. LOL) This is a controlled carb concept that adjusts for certain kinds of exercise styles. Here is a link you can also use to see if these ideas might help you.

http://www.wannabebig.com/printarticle.php?articleid=88

As to the hikeing and longer but lower intensity workouts you will find that it may take some time to get your body more adjusted to use of fat stores for energy but you will be amazed when that occurs.

Regardless...if you are LC "dieting" then you might not be getting the point for the long term. The trick is to make LC "eating" a way of life. If you only are LC to cut weight, I am not sure you will have enough time to understand it and make the mental and physiological changes needed to take full advantage of it.

Then again, if I am just being to picky about your word "diet", my humble appologies!