CLOCK and obesity due to melanocortin 4 receptor deficiency: For example, mutations or deficiencies in core clock genes such as Clock or Bmal1 result in obesity, lipodystrophy and/or glucose homeostasis abnormalities [5], [6], [7], [8], [9], and nuclear receptors central to regulating metabolic processes, such as PPARα and PGC-1α, affect the circadian clock [10], [11].