It sounds like your father and aunt probably have issues regarding weight. Please don't let them pass it on to you!

You're just a smidge over underweight, actually. You're very close to being underweight, according to the BMI.

I'm also 5'7, yet I'm 145 lbs. And yes, I'm fit, healthy, and thin.

It's VERY important to maintain a healthy weight, and if you let yourself become underweight (which will most likely happen at 1000 calories a day) without gaining weight again, you will have consequences.

1000 calories a day is going to cause you to lose weight... It depends on how active you are. If you're regularly active, it's recommended that you eat 2000 calories a day. If you're less active, you should still eat over 1500 calories a day...

I feel for you because I was in the same situation at a teenager. I was underweight, and suddenly my muscles and strength took a nose-dive, despite a very active lifestyle, because I couldn't support my metabolism, not to mention vitamin deficiencies I experienced. This was mostly because my father kept strict watch on what I ate and made sure I regularly exercised. He made comments on me being fat, too, even though I eventually learned that I was underweight.

Yeah, please don't listen to your family members. They'll make you physically sick if you let them get to you.