I am by no means a professional so if you are following a doctor prescribed regimine for fiber please follow their advice.
However, I feel if you follow the zone program and eat your whole foods Carbohydrates (specifically vegetables which are natually high in fiber) you may not need to take your Fiber One or could cut down on the dosage.
As for deserts, you may want to check out the Recipies listed in the Zone Lifestyle section. Remember that the deserts don't necessarrily need to be fat free to be in the Zone. Also fruits are an excellent desert, it just takes a change in mindset.
Here's a good desert you can try:
ZONE BANANA PUDDING
SNACK – 1 BLOCK
Block Size: Ingredients:
1 Protein 3 ounces firm tofu
1 Carbohydrate 1/3 banana
1 Fat 3 almonds
Place in food processor until blended. You can substitute the fruit with any kind but I have found banana works best.
Good luck to you!