Really, it depends on how much you weigh right now and how close you are to your ideal weight. I'll take supernu as an example since he's posted his weight here.
If supernu is, for ease of calculation, 300 lbs, and his ideal weight is 150 lbs, then there is 150 lbs of excess fat on his body. If he's eating 500 cals/day, and his body is burning 1500 cals/day, then he's getting 1000 cals/day from his bodily stores and 500 from food. This is a 2 lb/per week weight loss. Since the difference between 300 and 150 is large, the body can sustain this, no problem (not counting the negative effects of vitamin deficiency at this point).
As supernu gets closer to the goal weight, and he's still eating 500 cals/day, and let's say he's now at 200 lbs, the body will start to slow down the metabolism so that it doesn't "overshoot" and go into underweight territory (this is a simplification. 50 lbs is still a ways to go in practice). So now, let's say the body is only burning 1000 cals/day, or sustaining 1 lb of lost fat per week (500 cals/day bodyfat). At this point, if supernu were to boost calorie intake to 1000/day, and simultaneously boost physical activity (at an extra 500 cals/day) to give the metabolism a bump, the body might burn 2000 cals that day with 1000 coming from food and 1000 coming from bodyfat, bringing that day's rate of fat burn back up to the equivalent of 2 lb/week.
The bottom line is, the body is smarter than you, so if you try to cut calories to lose weight, it will spite you by burning fewer calories. Or think of it like a fire: give it more fuel, and it will burn hotter.
1) eat real food - more vegetables, moderate meat, moderate fruits, less grains, less sugar, less vegetable oils.
2) exercise - moderate intensity cardio, sprinting, heavy lifting, dedicated stretching and mobility.
3) live - relax, de-stress, meditate.
Disclaimer: I'm not professionally qualified to make any formal recommendations. I've just done my homework and I'm my own guinea pig. All of my data, unless otherwise cited, comes from a sample size of n=1 (me).