Your Ideal Body Weight is that weight at which your body is functioning at its best, and you are suffering from no illnesses. Therefore, being skinny or being within the healthy weight range does not mean you are healthy, just as being overweight does not mean you are unhealthy.
"A combination of factors determines our weight, and that's why it's difficult to set an exact ideal weight that applies to everyone. It's important to remember there's a range of healthy body weights. Aiming to keep within this means an end to aspiring to one magic weight you think you should be.