The prevalence of obesity has increased markedly in Korea during the past few decades. Korea is one of the most well-organized countries in terms of its National Health Insurance System (NHIS), which conducts screening examinations. Since the NHIS is unified and managed by the government, its data—contained in the National Health Insurance Database (NHID)—are centralized. The Korean government has recently encouraged researchers to access the NHID, conduct research, and write papers to convey their findings. Expanded research using the NHID could shed light on the future of big data research. In this review, I would like to present an overview of current trends in obesity research using the NHID.