Breakfast remains “the most important meal of the day,” according to a new study that found people who skipped out on it had double the risk of developing atherosclerosis compared to people who consumed energy-rich meals every morning.

Atherosclerosis refers to the hardening or narrowing of arteries, which can increase the risk of heart disease. The findings, published online last week in the Journal of the American College of Cardiology, were part of larger work, the Progression and Early Detection of Atherosclerosis study (PESA).

The PESA study aims to characterize the prevalence and progression of subclinical atherosclerotic lesions by monitoring participants for at least a six-year period.

Atherosclerotic plaques are found in the walls of arteries and first appear at a young age, but don’t show symptoms in their early phases, hence the term “subclinical.”

As part of the study, more than 4,000 adults in Spain, ages 40 to 54 and who all work in an office setting, completed a detailed questionnaire on their daily eating habits. Other information such as body mass index and cholesterol levels were collected, as well as data on smoking habits, education level and frequency of physical activity.

The participants were then grouped into three categories: those who either skipped breakfast entirely or consumed less than five percent of their day’s calories for breakfast (three percent of all participants); “low-energy” breakfast consumers who ate between five and 20 percent of the day’s calories at breakfast (70 percent of participants); and “high-energy” breakfast eaters who acquired more than 20 percent of daily calories in the morning (27 percent).

“Low-energy” breakfast participants typically had coffee and/or juice with fruit, toast or pastries while the “high-energy” group ate a combination of toast, fruit, ham, cereal, plus coffee and juice.

The team used imaging techniques to analyze any progression of atherosclerosis in six arteries, including in the heart, thighs and neck.

The study found that people who skipped breakfast or ate very little had 1.5 times more plaque in their arteries, compared with high-energy breakfast eaters. For some vascular regions, the number of plaques was as much as 2.5 times higher in participants who skipped breakfast or ate very little.

Those who skipped breakfast were also more likely to be overweight or obese, and reported having a worse diet overall than participants in the other two categories. Opting out of breakfast also correlated with other unhealthy behavior – such as smoking or excessive drinking – lifestyle habits that can cause atherosclerosis on their own. But the researchers did not the findings held true even after factoring in the overall quality of participants’ diets and other risk factors.

“The significant impact of breakfast on cardiovascular health is well known. What the latest PESA project has done is to evaluate the relationship between three distinct breakfast patterns and the presence of atherosclerotic plaques in asymptomatic individuals. The results suggest that skipping breakfast is an indicator of more generally unhealthy lifestyle habits, associated with a higher prevalence of generalized atherosclerosis,” wrote the researchers.

The study had several limitations, however. For example, the “breakfast skippers” were just a small percentage of all the participants. Additionally, a portion of the group that didn’t eat breakfast reported they were dieting, suggesting that at least some may have been skipping breakfast to lose weight.