You pick up two oatmeal options at the store. Both claim to be 100 percent whole grain oats. Both have 27 grams of carbohydrates. One takes 30 minutes to cook; the other is ready in 90 seconds. To you, it’s a matter of convenience—but to your body, they’re two entirely different foods. That subtle difference can affect everything from your energy and appetite to your blood sugar.

In recent years, carbs have gotten a bad rap—but not all of them deserve it. So what makes a carbohydrate truly healthy? It’s not just the number of grams on the label—it’s how the carb behaves in your body.