not eating enough?

i've been logging my food intake and exercise on dailyplate.com and i've been noticing that my time on the elliptical is burning approx 1050 calories.  well, my caloric intake is around 1000 cals/day so i've been netting negative calories.  could this be why i've been so tired lately?  i'm just not eating enough?  i get so confused on this whole actual vs. net cals.  thanks for all help and insight!!!

I read a recent thread about how accurate excercise machines are at truthfully measuring the amount of calories you burn and the concensus seemed to be that they were not terribly accurate overall.  That being said, you must be on the elliptical for a very long time to be burning any where near 1000 cal.  Sunce you are eating so little, it seems very  logical to me that you are eating too little to sustain your activity, much less lose weight.  I would encourage you to increase your calories slowly (increase by 100-200 cal/day over several days) so you can find the balance between your activity level and ability to lose weight.  Remember, your body needs fuel to lose weight - seems counterproductive, but true.  Good luck.