Previous animal studies have indicated that obesity adversely affects oocyte maturation and embryonic development30–34, which could be due to direct oocyte damage32,33,35 and the indirect effects of dysfunctional systemic maternal endocrinology and metabolism, such as hypercholesterolemia, elevations in glucose, insulin, or free fatty acids, and changes in adipokines30. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.