Generally, people are more pleasant when they're not hungry. And for some people, hunger can bring out the worst case of the grumps.
As it turns out, there is a scientific reason behind being "hangry" - that is, being angry when you're hungry. Your brain is evolutionarily wired to function on a full supply of glucose. When this supply is not replenished quickly enough, your brain perceives this as a life-threatening scenario, thanks to our primitive hunter-gatherer past. In such cases, the brain triggers the production of stress hormones and other chemicals that, together, contribute to the aggression and the short-tempered nature we experience when we've gone too long without nourishment.
One of the hormones that hunger triggers is adrenaline, which is linked with the "fight or flight" response. "Thus, hunger induces the stress response that initiates aggression, anger, and lack of control, or hanger," explained Brenda Bustillos, a dietitian and researcher at Texas A&M. "Hanger becomes a survival mechanism because our increased aggression and anger allow us to 'fight' for survival, or in other words, fight to obtain food."
Fortunately, you can quell that hangry beast by simply eating a snack. Snickers bar, anyone?