BMI wouldn't be a good measure for this. The correlation might be strong, but very fit or muscular people (for instance, weight lifters, fighters etc) can have

BMI wouldn't be a good measure for this. The correlation might be strong, but very fit or muscular people (for instance, weight lifters, fighters etc) can have rather high BMI - and you really don't want to filter those out. Waist-hip ratio might be a good alternative measure.