glycogen depletion

I read an article in the recent issue of Outside magazine about how sled dogs that run 100 miles day after day in the Iditerod are primarily using fat for fuel. Dogs don't use carbs for energy like humans... but could humans train to have their physiology work more like that of dogs?

Then, my Running Times magazine arrives and answers my question... enter article about low-carb training and how you can increase your long distance endurance by training your body to use fat when glycogen stores are low. Professional marathon runners have already found success with this. To teach the body to use fat, the key is that you need to train in a glycogen-depleted state.

The author gives three suggestions on how to do this:

1. Workout before breakfast on an empty stomach, two days per week.
2. On a double workout day, eat primarily fat and protein between the workouts and don't eat carbs during the workouts.
3. Do long runs up to 20 miles with only water.

She suggests to work into it gradually and not do all your workouts like this because it is stressful on the body at first. This all makes sense to me. If my body can use more fat stores during an Ironman, then I will have even more energy by supplementing carbs. I'm going to experiment with this a bit in my upcoming workouts and try to get my body as good at using fat as possible. I started this morning with a pre-breakfast run.

Run 7 miles with 4x800
[1:02 total time, 800's@3:16, 3:14, 3:19, 3:20]
Wow, those 800 splits amaze me. 3:14 might be a PR.

Strength Set #1
100 Pushups (knee)
100 Pullups (green band)
100 Situps
100 Squats
Broken up as sets: 10-10-13-13-10-10-9-25
[21:07]
 Strength Set #2
2x10 Single leg step ups with 25 lb plate
2x10 Side lunges with 10lb plate
45 leg press (9x5 reps starting at 110 and adding 10 lbs to failure at 180)

Swim 2500yd [47 min]
Recovery workout, nothing too hard or fast