How much exercise is necessary to build up one pound of muscles and to lose one pound of fat?

Answer 1

To gain one pound you need to eat 3500 extra calories.

Muscle is heavier than fat.

When on a diet, measure around the belly, a scale is not a good method of determning if your diet is working. There are charts all over the internet telling you how much calories you will burn doing a particular exercise.

Don't diet, the chances of it failing are overwhelming. A better choice is to change the way you live your life. The weight will come off naturally and you won't have to drive yourself crazy in the process.