Caloric intake Vs total calories

Piratepetetx

I was just wondering if you base how make calories you need vs eat while dieting. How low can you go and still stay healthy. I take in below 1600 cal and for the most part have an excess of 1000 due to swimming. Can I cut my calories more or will that effect how much weight I lose/ health. Are the calories I take in used to keep me healthy vs what I expend from cardio. Just questions I have.