Anything under 1800 kcal for a man is pushing it, that is so low that the organs are at risk of being starved.
Here's a calculator that can give a guideline for the resting metabolic rate (the only accurate way to determine it is via direct examination by experts.) On top of that comes all the moving around and exercise one does.
http://www.myfitnesspal.com/tools/bmr-calculator
Thanks for that calculator. I checked it out, and my resting metabolism rate appears to be under 1700 these days if the calculator can be believed.
Several years ago I went to a weight management program at a major university and they experimentally determined my resting metabolism (using a human exhaust gas analyzer - normal exhaust being from the lungs, not the other end).
I weighed well into the 320's at the time, and my resting metabolism just to keep all that fat going was up around 2400 calories per day.
They gave me recommended diet building blocks based on food pyramid ideas, and they allowed me to shift it away from carbs and toward protein since I always considered myself to be carnivorous first, and omniverous second.
This stuff worked for a month or two, and I did drop some weight, but it did not help me establish good habits because I was always thinking about how I could fudge the building blocks. I ended up regaining all I'd lost and more, landing squarely at 339 before finally sobering up and getting serious about not fooling myself.
Knowing about the high resting metabolism didn't help me because it just encouraged me to rationalize why I could lose weight on a 3000 calorie per day diet if I pursued normal activities. My physician warned me that the numbers were inordinantly high, and that I shouldn't count on that working, and I smugly pointed out that the numbers must be good because they were experimentally determined.
It is amazing how stupid we can be when we're convincing ourselves that the lifestyle we've fallen into is OK, especially if we can see many other people following similar lifestyles. It is easy to rationalize that we're normal.