"Like cortisol, HGH increases glucose and thus is suppressed during feeding. Fasting is a great stimulus.
During fasting, there is the spike in the early morning, but there is regular secretion throughout the day as well. Hartman et al also showed a 5 fold increase in HGH in response to a 2 day fast.
This HGH is crucial in the maintenance of lean mass – both muscle and bone. One of the major concerns about fasting is the loss of lean mass. This does not occur. In fact, the opposite happens – there is likely an increase in lean mass."