Losing weight

So I'm 5"8 and 205lbs.. considered obese by BMI but whatever. My legs are pure muscle with the tiniest bit of fat that I'm working on shedding off. I do have a little bit of tummy fat and I'm working on that too. I have a lot of muscle as I weight lift and workout daily. My goal weight is 160lbs which is in the "normal" bmi range.. but my doctor says I should be 140lbs.. I was 140lbs once and my ribs were so visible but she's not understanding that that is too skinny for me...