How blood sugar fluctuations affect mood, irritability, and behavior.
What the evidence says
- Blood glucose supply to the brain significantly affects mood and cognitive performance[1]
- Low blood glucose impairs memory, attention, and mood — the direction matters: those whose blood glucose was rising during cognitive tasks remembered more words than those whose levels were falling[1]
- Lower evening glucose predicted greater aggressive impulses toward a spouse — 107 married couples, 214 individuals, 4,051 person-days of diary data (b = −0.007, t(213) = −2.43, P < 0.02)[2]
- And more aggressive behaviour in a lab task (b = −0.008, t(213) = −2.82, P = 0.006). Note what each outcome is: “impulses” is pins pushed into a voodoo doll said to represent the spouse; “behaviour” is noise-blast intensity in a competitive reaction-time task. Both are established laboratory proxies. Neither is aggression toward a spouse[2]
- Effects persist when controlling for relationship satisfaction and sex differences[2]
- The “hangry” idea has this study behind it — a real, large, well-measured association between evening glucose and lab-measured aggression. What it does not have is a demonstrated mechanism[2]
- The authors explain the pattern through the glucose model of self-control — self-control draws on energy, glucose supplies it, low glucose leaves too little to override an impulse — and they cite Gailliot & Baumeister (2007) for it. That is their framing, and the glucose model it rests on is contested[2]