Is it possible to lose more than two pounds of fat a week when you're getting all the calories and nutrition you need each day and you walk more than four hours a day?

It's pretty unlikly. Here's why: 1 lb of fat is roughly 3500 calories. Plus the more lean you get that number goes up to lose the next lb. of pure fat. 300 calories is 35 miles of walking for the average weight person. If your walking 3 mph you'd have to walk a lot more than 4 hours. You could possible eat 1000 calories less than your maintance amount but you'd be pretty hungry, feel really tired and could possibly get sick on top of it. If you walked 3 mph for 4 hours a day 7 days you'd walk roughly 84 miles in a week. That would roughly be 2.5 lbs of fat in a week if you ate the perfect amount of food for your maintance. Keep in mind maintance will go down the more you walk. It would be better to do a little weight training in conjunction with your walking. Muscles burn calories. I hope that helps. A lb of pure fat is bigger than a Baseball size but not quite as big as a softball. So to lose 2 lbs of fat a week is doing pretty good. This assumes you do not have any thyroid problems and your body is buring fat like normal. Diet pills and other things could have changed your ability to burn fat in which it could be harder. I have my B.S. in Exercise Science. Yes, it's possible, but many factors play a role, like what food you're eating, your body size, etc. Physicians will tell you that losing more than 1-2 pounds a week can be both dangerous and lead to incresed weight gain down the line.