When people say "healthy weight", it is remarkably open for interpretation. My personal opinion, is that one should strive not just to remove as much fat as possible (because a lot of the fat types have purposes), but to remove as much visceral fat as possible.
Visceral fat is the type of fat that wraps around the inner organs, and wreak havoc on your general health. It increases the risk of diabetes, heart disease, stroke and dementia.
Measuring visceral fat is primarily done by a CT scan, or the more expensive option, a bioelectrical impedance machine. Getting one of these scans done can be beneficial, but it's not needed. Visceral fat can be managed by cardiovascular exercise, resistance training, and dieting. The best thing to do is just say "let's pretend I just had a scan, and it turns out I have a lot of visceral fat", and just get to work.