From avocado toast to zucchini muffins, a hearty breakfast is, well, heart healthy.

While previous studies have linked skipping the first meal of the day to coronary heart disease risk, a new study, published in the Journal of the American College of Cardiology, has found an association between skipping breakfast and atherosclerosis.

Atherosclerosis is the hardening and narrowing of the arteries due to plaque buildup.

Researchers in Madrid examined the diets of over 4,000 male and female volunteers who were free from cardiovascular or chronic kidney disease. Participants filled out a computerized questionnaire, which researchers used to estimate the usual diet of the participants.

Breakfast patterns were based on the percentage of total daily energy intake consumed at breakfast.

Three groups were identified:  those consuming less than five percent of their total energy intake in the morning (skipped breakfast and only had coffee, juice or other non-alcoholic beverages); those consuming more than 20 percent of their total energy intake in the morning (breakfast consumers); and those consuming between five and 20 percent (low-energy breakfast consumers). Among the participants, 2.9 percent skipped breakfast, 69.4 percent were low-energy breakfast consumers and 27.7 percent were breakfast consumers.

The researchers found atherosclerosis was observed more frequently among participants who skipped breakfast and was also higher in participants who consumed low-energy breakfasts compared with breakfast consumers.

Additionally, cardiometabolic risk markers were more prevalent in both of those groups compared with breakfast consumers.

Participants who skipped breakfast had the greatest waist circumference, body mass index, blood pressure, blood lipids and fasting glucose levels. They were also more likely to have unhealthy habits, such as smoking, alcohol consumption, and an overall poor diet, which can contribute to the development of atherosclerosis.

In addition, participants who skipped breakfast were also more likely to be hypertensive and overweight or obese. In the case of obesity, the study authors said reverse causation cannot be ruled out, and the observed results may be explained by obese patients skipping breakfast to lose weight.

"Between 20 and 30 percent of adults skip breakfast and these trends mirror the increasing prevalence of obesity and associated cardiometabolic abnormalities," said Prakash Deedwania, MD, FACC in an accompanying editorial comment. "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. Skipping breakfast can cause hormonal imbalances and alter circadian rhythms. That breakfast is the most important meal of the day has been proven right in light of this evidence."