Bariatric surgery is considered to be the effective treatment alternative conducted over the lifetime for reducing weight in patients with clinically morbid obesity. For many patients, the benefits of weight loss, including decreases in blood glucose, lipids, and blood pressure as well as increase in mobility, will outweigh the risks of surgical complications. But patients undergoing bariatric surgery have the least risk for long-term diet-related complications as reported in several studies. Thus, with an increasing number of severely obese patients undergoing bariatric surgery, the multidisciplinary healthcare system will need to be managed continuously. Many nutrition support specialists will need to become familiar with the metabolic consequences for the frequent monitoring of nutrition status of the patients. South Korea has a very short history with bariatric surgery, and relatively few studies have been conducted on bariatric surgery. Therefore, the objective of this report was to compare the nutrient intake, weight loss, body fat composition, and visceral fat before and after the bariatric surgery.