Yup, Piskie is spot on. Intermittent fasting is simply extended periods without food. Assume you're already fasting for at least eight hours a day while you sleep, and take it from there. You'll find a lot of information on fasting in the forums and Mark's articles, so I won't go into too much detail on the whys and wherefores here. The most common are either going 24 hours without food once or twice a week, or going 16 hours without food on a daily basis (half of which is spent asleep, remember), limiting your eating window to 8 hours a day.
Went primal for the weight loss, stayed for the quality of life!