A good first step towards improving your health is to bring your weight to normal. And BMI is supposed to be the best indicator of whether you are ‘normal’, ‘overweight’ or ‘obese’.
Here’s a useful calculator to calculate BMI.
You can also download a ready reference table where you can match your height and weight to find out your BMI. There are other more accurate ways which take into account gender and frame etc. but this one is a good start.
How to achieve and maintain a ‘normal’ weight is another story 🙂