At the end of the day - it depends on what your trying to achieve versus what works for you.
I know for a fact that i couldn't function on 800-1200 cals a day....I eat that much before 12 noon!!data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
I can lose weight/body fat on about 2200 cals a day - about 1lb a week. I train probably 5/6 times a week.
So 2200 is a calorie deficit for me - but 1500 might be for someone else. It's very dependant on what else your doing in terms of training/workouts/cycling etc versus what you eat.