BARCELONA — Mom always said breakfast was the most important meal of the day. As it turns out, she was right—but with a catch. New research suggests that when it comes to our morning meal, both portion size and nutritional quality play crucial roles in maintaining good health, especially for older adults at risk for heart disease.

While research has shown that skipping breakfast is linked to poorer overall diet quality and higher cardiometabolic risk, Spanish researchers wanted to explore an understudied area: how both the calorie intake and dietary quality of breakfast might affect cardiovascular health over time.

“Promoting healthy breakfast habits can contribute to healthy aging by reducing the risk of metabolic syndrome and associated chronic diseases, thereby improving quality of life,” says Karla-Alejandra Pérez-Vega, a researcher at Hospital del Mar and CIBER for Obesity and Nutrition, in a statement.

The investigation was part of the larger PREDIMED-Plus trial, which studies the effects of Mediterranean diet and lifestyle interventions on cardiovascular health.

The study included 383 adults aged 55-75 who were participating in the trial at the Hospital del Mar Research Institute in Barcelona. All participants had metabolic syndrome—a cluster of conditions including high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels that together increase risk of heart disease, stroke, and diabetes. They were also following a weight-loss lifestyle intervention based on the Mediterranean diet.

For three years, researchers tracked these individuals’ breakfast habits and health markers. They discovered something fascinating: people who ate either too little (less than 20% of their daily calories) or too much (more than 30%) at breakfast tended to fare worse than those who hit the sweet spot of 20-30% of their daily caloric intake during their morning meal.

By the study’s end, the differences were striking. Compared to the goldilocks group who ate just right, participants who consumed too little or too much at breakfast showed higher body mass index (BMI) measurements and larger waist circumferences. Their blood work also revealed higher levels of triglycerides (a type of fat found in blood) and lower levels of “good” HDL cholesterol.

But quantity wasn’t the only factor that mattered. Quality played an equally important role. Participants whose breakfasts scored low on nutritional quality—regardless of size—showed similar negative health trends. They too had larger waist measurements, less favorable blood fat profiles, and perhaps most surprisingly, decreased kidney function compared to those who ate more nutritionally balanced morning meals.

To assess breakfast quality, researchers used the Meal Balance Index, which scores meals based on nine nutritional components. The index uses Acceptable Macronutrient Distribution Ranges for proteins and fats, Daily Values for fiber, potassium, calcium, and iron, and World Health Organization recommendations for added sugars, saturated fats, and sodium. Each component receives a score from 0 to 100, with scores for potassium and saturated fat weighted double in the final calculation. Higher scores indicate better nutritional quality.

These findings, published in The Journal of Nutrition, Health and Aging, have particular relevance for older adults trying to manage or prevent heart disease. While previous research has established that eating breakfast is better than skipping it, this study suggests that simply eating any breakfast isn’t enough—both portion size and nutritional quality need careful consideration.

Interestingly, the study took place during a broader health intervention where participants were following a Mediterranean diet and trying to lose weight. Even within this generally healthy dietary pattern, breakfast composition made a measurable difference in health outcomes.

For those wondering what an ideal breakfast might look like, the study suggests aiming for that 20-30% sweet spot of daily calories. For someone eating 2,000 calories per day, that would mean a breakfast between 400-600 calories. Quality-wise, think balanced meals incorporating whole grains, lean proteins, healthy fats, and fruits or vegetables while limiting processed foods high in added sugars and unhealthy fats.

With metabolic syndrome and cardiovascular disease representing major public health challenges worldwide, understanding how simple dietary adjustments—like optimizing breakfast—could help manage these conditions is invaluable.

As our understanding of nutrition science evolves, it’s becoming clear that when we eat may be almost as important as what we eat. This study adds another piece to that puzzle, suggesting that front-loading our day with the right amount of high-quality nutrition might be one key to better metabolic health.

Perhaps mom’s advice needs a slight update.

“Breakfast is the most important meal of the day, but what and how you eat it matters. Eating controlled amounts—not too much or too little—and ensuring good nutritional composition is crucial,” says Álvaro Hernáez, researcher at the Hospital del Mar Research Institute, CIBER for Cardiovascular Diseases (CIBERCV), and professor at the Blanquerna Faculty of Health Sciences at Ramon Llull University. “Our data show that quality is associated with better cardiovascular risk factor outcomes. It’s as important to have breakfast as it is to have a quality one.”

Paper Summary

Methodology

Researchers followed 383 participants for 36 months, collecting detailed food records at baseline, 24 months, and 36 months. Participants recorded everything they ate and drank for three days (two weekdays and one weekend day) at each collection point. Breakfast was defined as any morning food intake, including both traditional early breakfast and mid-morning snacks. The research team analyzed these records for both the percentage of daily calories consumed at breakfast and the nutritional quality using the Meal Balance Index, which scores meals based on nine nutritional components.

Results

The study found clear patterns showing that eating either too little (less than 20% of daily calories) or too much (more than 30%) at breakfast was linked to less favorable health outcomes. By the end of the study, these groups showed higher BMIs, larger waist measurements, and less healthy blood fat profiles compared to those who ate 20-30% of their daily calories at breakfast. Similarly, those whose breakfasts scored low on nutritional quality showed poorer health markers, regardless of portion size.

Limitations

The researchers acknowledge several limitations. First, since this was an observational study, they can’t prove direct cause and effect—they can only show associations. Additionally, all participants were older adults with metabolic syndrome, so the findings might not apply to younger or healthier populations. The study also relied on self-reported food diaries, which can be subject to error or bias. Finally, since the study was conducted during a weight loss intervention, the results might be different in a population not actively trying to lose weight.

Discussion and Takeaways

This research breaks new ground by examining not just whether people eat breakfast, but how much they eat and what kind of nutritional quality they’re getting. The findings suggest that both quantity and quality matter significantly for metabolic health. The study’s results point to potential benefits of structuring breakfast to provide 20-30% of daily calories while focusing on nutritional quality. This could have important implications for dietary recommendations, especially for older adults managing cardiovascular risk factors.

Funding and Disclosures

The study was supported by various Spanish research institutions and the European Union. Some researchers reported connections to food industry organizations, including board memberships and grants from organizations like the International Nut and Dried Fruit Foundation and various research foundations focused on wine, nutrition, and alcohol. However, these connections were disclosed and the study design included measures to minimize potential bias.

The precise breakfast formula that could help protect your heart, according to science

New research from the Hospital del Mar and CIBER for Obesity and Nutrition in Barcelona, Spain, suggests that the quality and quantity of breakfast significantly impact cardiovascular health, especially for older adults at risk for heart disease. The study, part of the larger PREDIMED-Plus trial, found that eating breakfast within a 20-30% caloric intake range and with high nutritional quality leads to better health outcomes, including lower BMI, waist circumference, and blood fat profiles. The study also highlights the importance of quality breakfasts, regardless of portion size.