Anyone who's been on a diet knows that hunger can make you cranky. With less fuel, your brain doesn’t exert as much self control, so you let your impatience and irritation go unchecked.
Researchers speculate that such hunger-fueled anger could even affect your marriage. Brad Bushman, at The Ohio State University, and his international group of colleagues set up a study involving 107 married couples, using voodoo dolls to track how angry spouses felt toward each other. Over a period of 21 days, the couples had their blood glucose measured every night before they went to bed, and every morning before they ate breakfast, as a barometer of their hunger. The voodoo dolls were stand-ins for their spouses; each partner had 51 pins and poked the doll each night to represent how irritated he or she was at his or her spouse.
Who poked the most? Those who had the lowest glucose levels on average stabbed their voodoo partner more than twice as many times as those with the highest glucose levels. Even after the scientists controlled for how happy the spouses reported their relationship as being, the hunger-aggression connection remained strong.
“We don’t say that glucose levels explain everything, but we took repeated measures over the 21 days and found these pretty robust results,” says Bushman.
It’s possible that the people with higher glucose levels were simply more forgiving or feeling more generous after a fulfilling meal – levels of mood hormones like serotonin tend to go up after a meal, ushering in a feeling of satiety. But Bushman believes that the consistency of the results hint that something more may be involved, and that may have to do with how hunger can contribute to less self-control and more irritable behavior.
In the second part of the study, he and his colleagues asked the spouses to play a competitive computer game, and awarded the winning partner the opportunity to blast the loser with a cacophony of sounds, including dentist drills, sirens, and fingernails dragging across a chalkboard. The scientists told the participants they could make the sounds as loud or as quiet as they desired, and leave them on for as long as they wanted (researchers actually controlled the volume so no eardrums were harmed). Those who recorded the lowest glucose levels over the past 21 days were more likely to blast the sounds at higher volumes and for longer periods of time if they won than those who had higher glucose levels.
That skipping meals or cutting back on calories could escalate aggression among spouses leads Bushman and his colleagues to suspect that hunger could even be behind some cases of domestic violence, although the study did not go as far as to test that theory. But Bushman says the findings make it clear that low glucose levels, and its resulting lack of self-control, should be considered part of the constellation of factors that can contribute to marital strife. That means that people on diets should be aware of how their drop in calories can affect their mood and the way they interact with others, including their spouse. And, says Bushman, “If couples have something to talk to their spouse about, they should do it over dinner, or better yet, after dinner.”