Objectives The purpose of this study was to investigate the characteristics in obesity classification group of college students having health checkup by analyzing their BMI and blood test and determine the association between factors contributing to obesity and obesity according to BMI. Methods A group of 2992 test subjects took their medical examination and their body composition, height, weight, blood pressure were measured and blood test was done. With these results we diagnosed obesity, and analysed relationship between obesity and cholesterol, triglyceride, LDL (low density lipoprotein)-cholesterol, HDL (high density lipoprotein)-cholesterol, liver function, renal function and blood pressure. Results 1. Overweight individuals showed high total cholesterol, LDL-cholesterol, triglyceride, GOT (glutamic oxalacetic transaminase), GPT (glutamic pyruvate transaminase), Urea-nitrogen, Creatinine and low HDL-cholesterol. 2. BMI showed a significant association with other factors. BMI has a negative correlation with sex and HDL-cholesterol. BMI had positive correlations with other factors. 3. There was no relation between BMI and sex. Those six factors, liver function, cholesterol, blood pressure, kidney function, neutral fat, and blood sugar were related to BMI. Conclusions There was a significant relation between college students' BMI and their liver function, cholesterol, blood pressure, kidney function, neutral fat, and blood sugar. The diseases related to liver function, cholesterol, blood pressure, kidney function, neutral fat, and blood sugar were clearly associated with obesity.