Husbands and wives are are more likely to quarrel if they are "hangry" - hungry and angry, say scientists.
Experts believe low levels of blood sugar may be linked to marital arguments, confrontations and even domestic violence.
The antidote is to eat a carbohydrate snack or something sugary, suggesting that cake or chocolate might help to placate an angry spouse.
"People can relate to this idea that when they get hungry, they get cranky," said US lead researcher Dr Brad Bushman, from Ohio State University.
"We found that being hangry can affect our behaviour in a bad way, even in our most intimate relationships."
Dr Bushman's team conducted a bizarre study with 107 married couples that involved participants sticking pins into voodoo dolls representing their spouses.
Each husband and wife was allocated a doll and, acting alone, told to stick up to 51 pins in it at the end of each day, depending on how angry their spouse had made them.
At the same time, participants used a blood glucose meter to test their blood sugar every morning and evening. The experiment was repeated for 21 days.
The results, reported in the journal Proceedings of the National Academy of Sciences, showed that lower blood glucose in the evening coincided with more pins being stuck in voodoo dolls.
Wives tended to stick more pins in their dolls than husbands, though the difference was not significant.
"When they had lower blood glucose, they felt angrier and took it out on the dolls representing their spouse," said Dr Bushman. " Even those who reported they had good relationships with their spouses were more likely to express anger if their blood glucose levels were lower."
As if stabbing voodoo dolls was not enough, the scientists devised another experiment "within ethical limits" in which husbands and wives blasted each other with loud noise.
Participants played a computer game that involved seeing how fast they could press a button when a target square turned red.
The computer let them win about half the time. But the volunteers were told they were playing their spouses, and the winner of each trial could blast his or her opponent with loud and unpleasant noise played through headphones. The "winners" could also vary the volume and duration of the noise.
The noises were mixtures of sounds that most people hate, such as fingernails scratching a chalkboard, dentist drills, and ambulance sirens.
At their loudest level, they were on a par with a fire alarm and the longest lasted for five seconds.
Individuals with lower average levels of evening blood glucose subjected their spouses to louder and longer bursts of noise, the researchers found. This was true even after taking account of reported relationship satisfaction and differences between men and women.
Those volunteers who stuck the most pins in the voodoo dolls were also likely to deliver the loudest and longest noise blasts.
"We found a clear link between aggressive impulses as seen with the dolls and actual aggressive behaviour," said Dr Bushman.
He believes the self-control needed to prevent aggressive outbursts uses up energy in the brain, which may be unable to keep a lid on angry emotions if it lacks glucose "fuel".
"Even though the brain is only 2% of our body weight, it consumes about 20% of our calories," Dr Bushman added. "It is a very demanding organ when it comes to energy.
" It's simple advice but it works: Before you have a difficult conversation with your spouse, make sure you're not hungry."
British expert Jeremy Nicholson, professor of biological chemistry at Imperial College London, said: "It is not tremendously surprising that low glucose makes people grumpy - they are hungry after all, or feel so.
"Aggression is known to be associated with poor diabetic control and alcohol consumption also causes hypoglycaemia (low blood sugar) which can contribute to aggression, although the alcohol itself is the main agent."