NPY and obesity due to melanocortin 4 receptor deficiency: From 2008 to 2015, “food intake” (burst intensity 6.36), “free radicals” (burst intensity 3.36), “diet induced obesity” (burst intensity 4.82), “body weight” (burst intensity 5.4), and “neuropeptide Y” (burst intensity 3.47) gradually became the most important factors in the study.