Waist-to-Hip Ratio or WHR is a health risk indicator given by a person's ratio of the waist circumference to the hip circumference:
Waist circumference: measure the circumference of your waist at its smallest point, usually just above the navel.
Hip circumference: measure the circumference of your hips at their widest point.
For men, a waist-to-hip ratio of 0.9 or less, and for women 0.8 or less are considered safe. For both men and women, the risk of heart disease and other problems associated with being overweight rises sharply with a WHR of 1.0 or higher.
A high waist circumference is associated with an increased risk for type 2 diabetes, hypertension and CVD (cardio-vascular disease) in individuals with a BMI in a range between 25 and 34.9 (Overweight and Obesity-Class I).
The "high risk" cut-off points are:
Men > 102 cm ( or > 40 in);
Women > 88 cm ( > or 35 in).
Apple & Pear Shapes
Most people store body fat in two distinct ways: around the waist ("apple" shape) or around the hips ("pear" shape). For most people, carrying excess weight around their waist ("apple" shapes) increases health risks more than carrying extra weight below their waist ("pear" shapes).
However, overall obesity is still of greater risk than body fat storage locations or WHR. Hence the interest of the Body Mass Index.