Waist-to-Height Ratio (WHtR)
The waist-to-height ratio (WHtR) is calculated by dividing your waist size by your height. The WHtR may give a more accurate assesment of health for serious athletes, especially body builders, who have a higher percentage of muscle and a lower percentage of body fat, or for women who have a "pear" rather than an "apple" shape. A WHtR under 50.0% is generally considered healthy.

Current guidelines, as given by the World Health Organization, or the National Heart, Lung and Blood Institute, only give values for waist circumference. Those at substantially increased risk have the same risk as someone with a BMI of 30. Assuming the average male is 5' 9", and the average female is 5' 4", here are the waist cutoff values, and the corresponding WHtR

	Increased Risk	Substantially Increased Risk
	Waist (WHtR)	Waist (WHtR)
Men	37.0" (53.6%)	40.2" (58.3%)
Women	31.5" (49.2%)	34.6" (54.1%)

Here are some values of WHtR that I have come across:

Subjects	WHtR
Barbie Doll	25.0%
Ken Doll	36.0%
Female College Swimmers	42.4%
Male College Swimmers	42.8%
Willoughby Ideal	45.8%
WHO Increased Risk Females	49.2%
General Healthy Cutoff	50.0%
NHANES Risk Equivalent to BMI of 25	51.0%
WHO Increased Risk Males	53.6%
WHO Substantially Increased Risk Females	54.1%
NHANES Risk Equivalent to BMI of 30	57.0%
Willoughby Obese	57.7%
WHO Substantially Increased Risk Males	58.2%

Conclusions about the NHANES data were lifted from Am J Clin Nutr 2002 76 743. An interesting perspective on height-to-waist ratio is provided in Int J Obes Relat Metab Disord. 2003 May; 27(5): 610-6. Also see Prev Med. 2005 Feb; 40(2): 216-20. Hsieh SD, Muto T., The superiority of waist-to-height ratio as an anthropometric index to evaluate clustering of coronary risk factors among non-obese men and women.

As your weight changes, you can expect to lose about 1" from your waistline for each 6-8 lbs of weight loss.

Here's an excellent thesis on the predictive power of Waist-to-Height Ratio for overall fitness written by Captain Steven Swiderski at the Air Force Institute of Technology.