People who want a healthy heart should be mindful of not only what they eat, but when they eat, according to a new scientific statement from the American Heart Association (AHA).

The report is a response to the growing evidence that timing matters when it comes to heart disease risk, said Marie-Pierre St-Onge, the lead author of the statement. The various organs of the body have their own “clocks,” St-Onge explained, and that may affect how we handle food at different times of the day and night.

“For example, later in the evening, it’s harder for the body to process glucose [sugar], compared with earlier in the day,” said St-Onge, an associate professor of nutritional medicine at Columbia University in New York City.

The new statement highlights what’s known — and what’s not — about meal timing and heart health. The statement lacks specific rules, such as “Never eat after 8 p.m.,” or “Everyone should eat breakfast.”

It does, however, suggest that people spread out their calories over a “defined” period of the day — as opposed to either eating a lot over a short period, or grazing from morning until night. Based on the evidence, the AHA says, it’s probably a good idea to get a large share of your calories earlier in the day.

“A long fasting duration at night is better than a long fast during the day,” St-Onge said.

But there’s no declaration that breakfast is the most important meal of the day.

The evidence, St-Onge said, is just not clear enough to make specific recommendations on breakfast.

A number of studies have found that breakfast eaters are generally healthier than breakfast skippers: They tend to weigh less, have better blood pressure and cholesterol numbers, and have lower risks of type 2 diabetes and heart disease, according to the AHA.

The problem is, those studies don’t prove that breakfast deserves the credit. And few trials have actually tested the effects of “assigning” people to eat breakfast, the AHA says.

Based on what studies have been done, adding breakfast doesn’t seem to aid weight loss, the report said. Of course, if breakfast skippers simply add an extra meal to their day, they’ll gain weight, St-Onge pointed out. A few small trials have, however, suggested that breakfast can help regulate blood sugar and insulin levels, according to the AHA.

Sonya Angelone is a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics. And she was clear in her support of eating breakfast.

“I think it’s very important to eat breakfast every day,” Angelone said.

Just as important, she said, is to hydrate after a long liquid-free night. Coffee does “count,” she noted, but a glass of water is better. According to Angelone, breakfast is critical because it’s hard to get all the nutrients you need in just two meals a day — even if you snack.

That raises another question: Should people eat “three square meals,” or is it better to stick with small, but more-frequent meals?

That’s not clear, according to the AHA.

Studies that track people in the real world have found that those who eat more often during the day have a lower risk of obesity and better cholesterol levels. On the other hand, the AHA says, small trials that have tested the effects of altering meal frequency have mostly come up empty. When daily calories are kept constant, meal frequency may not affect people’s weight, levels of “good” HDL cholesterol or other factors that affect heart health.

Of course, there is no one-size-fits-all approach to eating, St-Onge said.

Some people, she noted, do well with “grazing” throughout the day — as long as the food choices are healthy, and they do not keep grazing until midnight.

“If you’re someone with good control over your diet, maybe grazing is a good idea,” St-Onge said. “But if it’s difficult for you to stop eating once you start, it’s probably not a good idea.”

According to Angelone, frequent eating may not be wise for people with resistance to insulin — the hormone that regulates blood sugar. Insulin resistance is seen in people with type 2 diabetes or “pre-diabetes.” If those people eat often, Angelone explained, their insulin levels may never have a chance to drop. In general, St-Onge said, “mindfulness” is critical. Often, people eat not because they’re hungry, but to deal with emotions, she said.

“Ask yourself why you’re eating,” St-Onge said. “Is it because you’re stressed or sad or bored? Ask yourself whether you’re really hungry right now.”

The statement was published online Jan. 30 in the AHA journal Circulation.