Several studies have found that people with excess abdominal fat have a greater chance of dying from cancer or heart disease than people with smaller waistlines. A Harvard study of 44,000 women in the Nurses’ Health study found that women with a waist size equal to or greater than 35 inches (89 cm) were approximately twice as likely to die of heart disease as were women with a waist size less than 28 inches (71 cm), regardless of their Body Mass Index (BMI). Similarly, women with a waist size equal to or greater than 35 inches also were twice as likely to die of cancer as were women with a waist size less than 28 inches.
Another study examined the association between waist circumference and mortality among 154,776 men and 90,757 women aged 51-72 years in the NIH-AARP Diet and Health Study. A large waist circumference was associated with an approximately 25% increased mortality risk for both men and women. The waist circumference-mortality association was found in persons with and without prevalent disease, in smokers and nonsmokers, and across different racial or ethnic groups (non-Hispanic Whites, non-Hispanic Blacks, Hispanics, and Asians).
People with a normal BMI and a large waist circumference, 40 inches (102 cm) for men, and 34.6 inches (88 cm) for women, had approximately 20% higher mortality risk than those with normal BMI and normal waist size.
Many scientific studies focus on the absolute size of the waist instead of calculating a measure that provides the anthropomorphic proportions of the subjects. The average height of persons in the U.S. is 176.3 cm (69.4 inches) for males, and 162.2 cm (63.8 inches) for females. From these measurements, we can calculate that the Waist-to-Height ratio associated with 20% higher mortality is 0.58 for males and 0.54 for females. In general, a normal Waist-to-Height ratio is less than 0.50. Waist-to-Height ratios of 0.55 and over indicate excess abdominal fat which is associated with early death.
 Koster A, Leitzmann MF, Schatzkin A, Mouw T, Adams KF, van Eijk JT, Hollenbeck AR, Harris TB, Waist circumference and mortality, Am J Epidemiol. 2008 Jun 15;167(12):1465-75. PMID: 18417494
 Human Height