Skipping breakfast could lead to hardening of the arteries, raising the risk of heart attacks, scientists claim.
And their research further suggests why breakfast really is the most important meal of the day.
Missing a morning meal is linked to an increased risk of atherosclerosis, which is the hardening and narrowing of arteries due to a buildup of plaque, new research shows.
A vast amount of research has been carried out into the health benefits of eating breakfast, but researchers say it is the first study to link the meal to atherosclerosis.
Study author Dr Valentin Fuster said: "People who regularly skip breakfast likely have an overall unhealthy lifestyle.
"This study provides evidence that this is one bad habit people can proactively change to reduce their risk for heart disease."
Researchers in Madrid examined male and female volunteers who were free from cardiovascular or chronic kidney disease.
A computerised questionnaire was used to estimate the usual diet of the participants and patterns were based on the percentage of total daily energy intake consumed at breakfast.
Three groups were identified during the study - those consuming less than five percent of their total energy intake in the morning, those consuming between five and 20 per cent and those consuming more than 20 per cent.
The first group skipped breakfast and only had coffee, juice or another non-alcoholic drink, the second were 'low-energy breakfast consumers' and the third were deemed 'breakfast consumers'.
Of the 4,052 participants, 2.9 percent skipped breakfast, 69.4 percent were low-energy breakfast consumers and 27.7 percent were breakfast consumers.
Research revealed atherosclerosis was more frequent in those who skipped breakfast and also higher in those who had low-energy breakfasts compared to breakfast consumers.
It also showed cardiometabolic risk markers were more prevalent in those who skipped breakfast and low-energy breakfast consumers compared to breakfast consumers.
Participants who skipped breakfast had the greatest waist circumference, body mass index, blood pressure, blood lipids and fasting glucose levels.
Dr Jose Peñalvo, the study's senior author, said: "Aside from the direct association with cardiovascular risk factors, skipping breakfast might serve as a marker for a general unhealthy diet or lifestyle which in turn is associated with the development and progression of atherosclerosis.
"Our findings are important for health professionals and might be used as a simple message for lifestyle-based interventions and public health strategies, as well as informing dietary recommendations and guidelines."
Further findings showed participants who skipped breakfast were more likely to have an overall unhealthy lifestyle, including poor diet, frequent alcohol consumption and smoking.
They were also more likely to be hypertensive and overweight or obese, according to the study, published in the Journal of the American College of Cardiology.
In the case of obesity, the study authors added reverse causation cannot be ruled out and observed results may be because obese patients skipped breakfast to lose weight.
Dr Prakash Deedwania, professor of medicine at the University of California, said: "That breakfast is the most important meal of the day has been proven right in light of this evidence."
He added: "Between 20 and 30 percent of adults skip breakfast and these trends mirror the increasing prevalence of obesity and associated cardiometabolic abnormalities
"Poor dietary choices are generally made relatively early in life and, if remained unchanged, can lead to clinical cardiovascular disease later on.
"Adverse effects of skipping breakfast can be seen early in childhood in the form of childhood obesity and although breakfast skippers are generally attempting to lose weight, they often end up eating more and unhealthy foods later in the day."