Lack of sleep triggers hormones leptin, ghrelin and cortisol in your body to crave for fatty foods and carbohydrates. These hormones control your appetite directly and a lack of sleep puts them into high gear where you are feeling more hungry than necessary.

http://www.canada.com/health/Dozing+diet+Sleep+diet+works+research+shows/2009252/story.html

Hypothetically, the major reason that parents of new born babies experience a rapid weight gain is that their adult sleeping patterns are constantly disrupted by a crying baby.

Then how do you explain celebrity moms that lose weight quickly after give birth? That would be an idiotic question because they have the time and money to work with personal trainers, chefs who cater to their every dietary need, and full nannies that tend to the baby 24/7. A celebrity mom’s sleep is never interrupted unless they allow themselves to be interrupted at night by the baby.