Although I only tried for a couple of weeks, keeping my fat at about 70-80% of calories, protein the lower end of moderate and carbs very low, I didn't feel very good. I gained back about 7lbs. I just found I was hungrier and it was easier to eat more calories seeing that fat is denser than carbs and protein. Although I had a week of a family emergency where I had to stay vegetarian while with family, I have been mostly eating more protein (read meat), way more veggies, more avocado, and even a little white rice and potatoes. I have just about cut out the rich fats - butter and oils - and cut out dairy. I also had to cut way back on olives because I realised that the low quality salt used in their processing seems to cause me to retain water. Maybe if I tried very high fat again it would work, without oil and butter, but I find it difficult to eat less protein/meat and still feel satisfied. Also cutting down on veggies, including root veggies such as carrots, swedes, beets etc was not good for satisfaction levels. Oh and I lost all the weight I gained back plus an extra couple of pounds.
Primal since May 2012. Loving life and down 50lbs.