You can reeeeeely smooth out those first few days, which are the toughest for anyone starting a fast, by doing a pre-cleanse diet for 3-5 days. Just eat very simply, fruits and veggies plus plenty of pure water... fresh juices are great too. I ate this way for 30 days prior to my 60 day mega fast and never had a problem the first week:
Breakfast: Fresh fruit/natural yogurt smoothie
Lunch: Big fresh veggie salad dressed with lemon, good oil, garlic and Sea Salt
Din din: All the homemade vegetarian vegetable soup you want
With juice between you are never hungry, though if you are a carboholic you will crave them... DON'T forget to TAPER off that coffee or other caffeine source! I do it over three days and completely eliminate the famous caffeine headache.