In this study, we assessed the associations among demographic characteristics, measures of adiposity and body composition, serum creatinine, and cystatin C before and after substantial medical weight loss in individuals with NFG, IFG, and T2DM, and described the impact of severe obesity and weight loss on GFR estimated using creatinine-based and cystatin C-based equations indexed to 1.73m2 BSA and indexed to actual BSA. Here, CST3 is linked to obesity due to melanocortin 4 receptor deficiency.