The researchers used weight (in kilograms) divided by height (in meters squared) to determine each patient's body mass index (BMI). They considered people with BMIs of 25 kg/m2 to 30 kg/m2 to be overweight and people with BMIs of 30 kg/m2 or greater to be obese. The researchers also assessed other factors in each patient, such as kidney function, blood sugar level or diabetes, blood pressure, and smoking. They then compared the time it took to develop ESRD in normal weight, overweight, and obese patients, taking into account these other factors.