It's a pretty complex system that's not just related to a few hormones but several groups of hormones. Lack of sleep is also related to depleted levels of human growth hormone (HGH) which are replenished during periods of deep sleep. This depletion leads to an increase in somatostatin levels which inhibits a whole heap of regulatory hormones to do with metabolism (eg: thyroid stimulating hormone, insulin, gastrointestinal hormones) - it actually slows it down!!
Lack of sleep also increases production of ghrelin (another hormone which induces hunger - especially for carbs) and reduces leptin levels (inhibits hunger). Ahhh.....so now we know why we crave biscuits, or toast, or chocolate late at night with our cuppa!
Leptin is released by adipose (fat) cells to say "I'm full - don't feed me anymore!" Now you see a problem here?
And for those who don't know what NPY is (I didn't either...so I had to look it up) - it is Neuropeptide Y which plays a role in energy balance. High levels of NPY in cerebrospinal fluid (protects the brain and spinal column) are associated with high food intake and decreased physical activity.
High sugar and high fat diets are also linked to increased production of NPY.
Hmmmmm........now I know why I put on weight after nightshift even though I don't eat anything more than usual!