To find your BMI, see the table on page 2 of this article. BMI's of 19-25 are a range of weights which is associated with comparable minimal health risk. Interestingly being significantly underweight is risky, but so is being overweight. The risk begins to rise above BMI of 25, and more sharply beyond a BMI of 30, where medical intervention is generally is felt to be justified. Morbid obesity begins above BMI's of 40.
Waist circumference is an added measure.
Men with a waist of over 40 inches and in women over 35 inches begin to carry significant health risk. Clearly there is no single medically perfect weight for any of us to aim for, only as determined by modeling agencies. Feeding behavior is one of the most basic biologic drives and instincts. If it were not overwhelmingly strong, our species would not have survived. Genetics generally determines more body shape than total weight.