The Atkins diet - and others that limit carbohydrates - are likely to put you in a bad mood, research has found.
Pasta: not part of the Atkins diet
A team from the Massachusetts Institute of Technology says carbohydrates help to stimulate production of a key brain chemical called serotonin.
It controls our emotions, and a shortage can lead to mood swings and depression.
The Atkins diet has become hugely popular despite concerns over its effect on health.
Some experts are concerned about whether it might trigger diabetes and kidney damage in the long term.
Researcher Dr Judith Wurtman said: "When serotonin is made and becomes active in your brain, its effect on your appetite is to make you feel full before your stomach is stuffed and stretched.
"But serotonin is crucial not only to control your appetite and stop you from overeating; it's essential to keep your moods regulated."
Antidepressant medications are designed to make serotonin more active in the brain and extend that activity for longer periods of time to assist in regulating moods.
Because carbohydrates raise serotonin levels naturally they effectively act like a natural tranquilizer.
The brain makes serotonin only after a person consumes sweet or starchy carbohydrates.
However, these carbohydrates must be eaten in combination with very little or no protein.
Essential for a good mood?
So a meal like pasta will allow the brain to make serotonin, but eating chicken and potatoes will actually prevent serotonin from being made.
This may explain why people may still feel hungry even after they have eaten a 20-ounce steak.
Their stomachs are full, but their brains may not be making enough serotonin to shut off their appetites.
A lack of carbohydrate may have more impact on women than men, as women have much less serotonin in their brains.
Dr Wurtman said some people, who she dubbed carbohydrate cravers, need to eat a certain amount of carbohydrates to keep their moods steady.
They tend to experience a change in their mood, usually in the late afternoon or mid-evening, she said. And with this mood change comes a yearning to eat something sweet or starchy.
According to Dr Wurtman's clinical studies, if the carbohydrate craver eats protein instead, he or she will become grumpy, irritable or restless.
Filling up on fatty foods like bacon or cheese is no answer. That will just make you tired, lethargic and apathetic.
Dr Wurtman said: "When you take away the carbohydrates, it's like taking away water from someone hiking in the desert.
"If fat is the only alternative for a no - or low-carb dieter to consume to satiate the cravings, it's like giving a beer to the parched hiker to relieve the thirst - temporary relief, but ultimately not effective."
Dr Wurtman has founded her own weight-loss programme called Adara on the back of the serotonin research. It advocates carbohydrates and low fat foods, along with yoga and personalised fitness programmes.
Dr Stuart Trager, chairman of the Atkins Physician Council, said clinical research had contradicted Dr Wurtman's findings. He cited one study which found controlling carboydrate intake improved the mood of 51% of those who took part.
He said: "We would hope that medical practitioners and those who participate in low carbohydrate lifestyles will recognize that mood, and energy levels are related to many factors, and as such reaching conclusions like this is not practical.
"Controlling carbohydrates helps people manage their weight, improve body image and stabilizes blood sugar.
"Additionally, it is important to remember that serotonin, the chemical these researchers are discussing is made within the body from ingested protein, rather than carbohydrates."
Brigid McKevith, a nutrition scientist at the British Nutrition Foundation, told BBC News Online the effect of diet on serotonin was far from clear cut.
She said: "It has been suggested that a meal high carbohydrate may lead to an increase in serotonin, but the effect is unlikely to be significant when eating a meal because as little as 2-4% of calories from protein will prevent this.
"It is worth remembering that many foods - such as milk, beans and even potatoes - contain both carbohydrate and protein."