Hi Woodrabbit,
First of all, congratulations on choosing to breastfeed your baby... s/he will thank you for it
This way of eating is perfectly compatible with breastfeeding. It centers around feeding yourself the same types of foods for which the human body has evolved over the eons, and up until a generation or two ago, ALL babies were breastfed. Just make sure you're getting a good variety of fish, meat, poultry, nuts, seeds, fruits, and vegetables. Make sure you're including plenty of green leafy veggies for calcium, especially if you choose to cut out dairy foods (note that some "modern cavepeople" still consume some dairy, if their bodies tolerate it well). A good multi-vitamin, fish oil supplement, and extra vitamin D won't hurt, either.
This is also an ideal way of eating for people of any weight who wish to become healthier. People who are obese often enjoy the most dramatic results from changing over to this lifestyle. Check this link for examples and inspiration:
http://www.marksdailyapple.com/the-book/success-stories/ Welcome to the Tribe, and do keep us posted regarding your progress!