Are body parts proportional to weight?

No: The shape of the body is mostly dictated by the genetic make-up. Also where someone loses or gains weight is also dictated by the genetic make-up. However, for most part, abdominal fat is linked to obesity, diabetes, heart disease, and many more chronic diseases. Therefore loss of abdominal fat and fat around waist to hip (more around waist) is very important no matter what the body proportions ar.