Let them eat cake: Blood sugar and emotions

http://www.theguardian.com/commentisfree/2014/apr/15/stick-pins-in-partner-low-blood-sugar-diet-brain

The brain metabolises glucose and cannot store energy so low blood sugar levels can affect your emotional state and your self-control.  Researchers have found that low blood sugar levels increase the amount of aggression between partners and participants on a task.

http://www.ncbi.nlm.nih.gov/pubmed/21064166