We all know we crave junk food when we're tired.
Now, science knows why.
It comes down to the balance between the hormones leptin, which suppresses appetite, and grehlin, which increases hunger.
The new research says a lack of sleep spikes the grehlin, making us hungry.
But the ghrelin binds to the same brain receptors as the active ingredient in marijuana, triggering the craving for fatty, starchy, sugary foods, similar to the 'munchies' pot smokers experience.
Lack of sleep triggers junk food cravings, research says