Before I start, I want to make something clear: Your ideal body weight does not translate into being skinny or getting back to the size you were in high school. Instead, it's about being healthy and minimizing any risks for health problems—especially if you are genetically predisposed, like diabetes, high blood pressure, heart disease, autoimmune and inflammatory disorders, and so forth.
Next, it's important to know that you can be healthy at any age and any size, but ultimately, figuring out your ideal body weight involves doing some body measurements, assessing how you feel in your body both mentally and physically, and taking into account any health risks you may have. The National Institutes of Health (NIH) recommends that to assess your weight with regard to health risk, so it's important to get an estimate of your body fat, the circumference of your waist, and what your risk factors may be for disease. Here's how to do it: