Obesity is primarily defined by excess of body fat. Skinfold test, bioelectrical impedance analysis, and dual energy X-ray absorptiometry are useful clinicial tests for determining body fat volume or rate. It has shown that visceral fat or abdominal obesity strongly correlated with insulin resistance and cardiovascular diseases. So, visceral fat area at the level of umbilicus by CT is usually assessed as a risk factor of lifestyle-related disease or atherosclerosis. In obese subject, excess of fat accumulation is observed in muscle and liver, which are associated with insulin resistance. Thus, intrahepatic and intramyocellular lipids recently have been measured by 1H-MRS method as the useful markers of insulin resistance.