This article is from the Aerobics Fitness FAQ, by firstname.lastname@example.org (Robles) with numerous contributions by others.
What you weigh is not as important as the percentage of bodyfat to
lean tissue. You can be overweight without being overfat and vice
versa. Since muscle weighs more than fat, and you want to have firm
muscles throughout your body, you may weigh more than you thought
was average for your height and build. There is still much
controversy over what is "ideal" bodyweight. While some body fat is
essential to sustain life, it is generally thought that a healthy
bodyfat percentage for males is 8-20% and for females is 13-25%.
Source: ACE Instructor Manual, 1993, p.178