Breakfast is the most important meal of the day — we’ve all heard it before. Yet, in the hustle and bustle of modern life, many of us opt for a quick snack in the morning or forgo the meal altogether.

But science continues to illuminate the mysteries of the human body and how it interacts with nutrients. A recent study from Spain has zeroed in on what may be the perfect breakfast recipe for tapping into health benefits. It’s partly about the ingredients and partly about size.

Researchers studied a group of about 400 adults ranging in age from 55 to 75. They found participants whose breakfasts made up between 20% and 30% of their daily caloric intake benefited the most. This group had a lower average body mass index, smaller waists, higher levels of HDL, or “good,” cholesterol, and lower levels of unhealthy triglycerides in their blood.

As far as what to eat? It matters. Study participants were scored on nine nutritional considerations, and those with the lowest scores, regardless of meal size, had larger waistlines and worse blood-fat profiles than those who ate balanced, healthy breakfasts. Less nutritional breakfasts also resulted in decreased kidney function.

Researchers said the findings are important for older adults. The right balance of breakfast quantity and quality contributes to healthy aging by reducing the risk of chronic diseases like heart disease, stroke, and Type 2 diabetes.

So, remember — eating breakfast is better than skipping it. But breakfast is best when we pay heed to the amount and quality of food we’re eating and relying on to fuel our day.