1500 cal/day sounds like a very short term experiment to me.

What LitTrog said about the basal metabolic rate and then doing the non-program food log for a week.

If such things are in your diet (64 ounce Big Gulp, coffee drinks that include anything other than a sweetener and cream, eating before bed, chips, etc.) you should eliminate them at once.

Ideally you find a balance between your energy expenditures and your fuel intake. More cardio/activity and a small reduction in calories is usually the answer.

Try lifting more frequently but lighter.