The World Health Organization classifies obesity as anyone with a body mass index (BMI) of 30 or above, and every 5-point increase in BMI increases your risk of cancers of the thyroid, kidney, colon, skin, gallbladder, and many others. A higher BMI also increases your risk of cancer mortality, particularly because obesity often comes with cardiovascular diseases and diabetes.
However, it might not necessarily be about BMI and more about white adipose tissue and visceral fat. White adipose tissue stores energy as fat and promotes inflammation and cancer development. Visceral fat is found around the organs (rather than subcutaneous fat that’s more visible and near your skin’s surface) and secretes more adipokines that could lead to inflammation and cancer. If you have more visceral fat, you have a 70% higher risk of developing pancreatic cancer than someone whose fat is in the hip region.
BMI doesn’t distinguish between visceral and subcutaneous fat, and it also doesn’t know how much lean muscle you might have. Instead, researchers can get a better estimate of visceral fat by measuring your waistline or waist-to-hip ratio. Regardless of BMI, some people might have an increased risk of cancer if their waist circumference or waist-to-hip ratio is higher. A 2023 study in JAMA Network Open found that your waist-to-hip ratio can better predict your risk of early death than BMI.