Wait, you mean you're only consuming 500/day total? Not just a 500/day
deficit?
Yeah, do please be careful and keep in mind that healthy weight loss rates are in the 1-2 lbs/week range (which translates to the 500/day deficit from your
maintenance caloric intake). If you keep a more intense fasting diet routine than that, it's going to mess with all kinds of hormones and likely have unexpected side effects like increased irritability, headaches, loss of sleep, loss of concentration, etc. This can be especially bad for women and result in amenorrhea (loss of menstrual cycle). You don't even have to go as low as 500/day to get that; I know someone who experienced exactly this condition, and after realizing the cause, it was scary enough to quickly snap her back into a more sustainable diet.