Anyone who aims for a healthy weight knows one key is to eat only when you are truly hungry. Eating for other reasons—you’re bored or stressed or don’t want to waste food—is a ticket to gaining weight.

But new research has discovered another reason to eat only when you’re hungry. It’s better for your body right away…every time you eat.

When you are moderately hungry before a meal, your blood sugar doesn’t rise as high as it does when you’re not really hungry but eat anyway, finds a new study. At University of Illinois in Chicago, 45 college students were asked to not eat for at least two hours, rate their hunger and then eat a dinner roll and a soda (a high-carb snack that tends to raise blood sugar). Afterward their blood sugar was tested. The study was repeated a week later to improve accuracy.

Results: Participants who said that they were pretty hungry had a lower level of post-snack blood sugar than those who said they weren’t. That’s a good thing, because postmeal blood sugar spikes damage cells, which, over time, can contribute to the risk of developing diabetes and cardiovascular disease.

What’s going on? While human studies haven’t teased out the physiology, animal research finds that cutting back on calories leads the hormone ghrelin to go up. It’s a well-known hunger hormone in humans, too. But ghrelin does more than make us hungry—it improves the efficiency with which the body moves glucose (sugar) from the bloodstream into the muscles, where it’s needed. In layman’s terms, when you’re hungry, your body is primed to digest a meal.

Getting ravenously hungry, however, may backfire. In that case, your body reacts by keeping blood sugar away from muscles to make sure there’s enough sugar for essential organs, such as the brain. Indeed, in the study, those who were very hungry had higher blood sugar levels after the snack than the moderately hungry. They reacted more like those who weren’t particularly hungry to start with.

It’s the first such study, so more research is needed to confirm and expand the results. But we already know that getting in touch with your hunger is a good way to guard against mindless eating—and the weight that often follows.

The takeaway: Eating when you are moderately hungry is not only best for weight management but may protect you from diabetes and heart disease, too. And there’s no benefit to waiting until you could eat a horse.