So working on this basis, if maintenance without exercise is 2000 (for example), a deficit of 20% and associated weightloss could be achieved by burning 500 calories through exercise while keeping intake at 2000. Is this correct?
That would be true. A deficit can be created with a decrease in caloric intake, and increase in activity, or any combination of the both. An energy deficit is a deficit any way you slice it.
Remember though, when someone says 15 calories per pound of bodyweight to determine maintenance, that is assuming a certain level of activity into the equation.
Finding maintenance, unless you are hooking your self up to a machine, is based simply on estimations. An easy way to know if you are at maintenance is to eat how you normally eat for 2 weeks or so and see which direction the scale heads. Stays the same, you are maintenance, goes up, you are in a surplus, goes down, you are in a deficit.
In that case, I will stick to SS for now. I haven't done much in the way of exercise for the last few months, so I'm pretty much starting from scratch. How do you judge when it's time to step up to more intensive exercise?
I don't think I can give you a concrete answer to this question. If you wanted to be systematic about it, once you can perform a steady state aerobic activiy for 30-60 minutes on a consistent basis at a relatively high intensity (as for as steady state is concerned), then you can start experimenting with interval and high intensity interval training.
In reality, almost ANYONE who is starting a new exercise program should be cleared by a doc IMO. Can never be too safe. This said, if you are generally healthy, as soon as you build a base of conditioning up, you can begin experimenting with some more intense exercise.
As far as diet is concerned, is there a reliable way of working out what my maintenance level is? The program I'm using to record my calorie intake has suggested 1844, but that seems a bit low. I'm 5'2", 157lb, 33 years and not working at the moment, so I spend most of my life in front of the pc.
When I used to train, my favorite thing to do with someone in terms of diet was have them track their intake for 2 weeks, as I said above, while monitoring weight. Problem with this is, based on empirical evidence.... MOST people fudge their intakes unfortunately, which only hurts them in the long run.
I really would not spend too much time finding a number that is an estimate anyhow. If 14-16 calories per pound seems really high to you for maintenance, chances are, you have been eating a lot less than this, and because of this, your metabolic rate is actually slower. If it seems about right, just go with it.
I always say: Remember, you are not signing a contract. Everything about nutrition and fitness is a trial and error process. Even I am constantly changing my approach. If you are not getting the desired effects a couple of weeks into it, you make the necessary changes.