Not all carbohydrates are created equal. When you eat them, your body breaks them down into glucose, a type of sugar that enters your bloodstream. But how quickly this happens depends on the food. Some foods send your blood sugar on a rollercoaster ride, while others provide a slow, steady stream of energy.

To measure this effect, we use the Glycemic Index, or GI.

Think of it as a rating system for carbs, on a scale of 0 to 100. Foods that break down quickly and cause a rapid spike in blood glucose have a high GI. Foods that break down more slowly, releasing glucose gradually into the bloodstream, have a low GI.

The difference in blood sugar response between high-GI and low-GI foods can be significant. A high-GI food leads to a quick spike and then a sharp drop in blood sugar. This can leave you feeling tired and hungry again soon after eating. In contrast, a low-GI food causes a smaller, more gradual rise and fall.

This steady energy release is why paying attention to GI can be helpful for managing overall health. Choosing lower-GI foods can help maintain more stable blood sugar levels throughout the day, which supports consistent energy and can help control appetite.

So how is a food's GI value determined? Scientists give a group of people a serving of the food containing 50 grams of digestible carbohydrates. They then measure the volunteers' blood sugar levels over the next two hours. The result is compared to the effect of 50 grams of a reference food, either pure glucose or white bread, which has a GI value of 100.

Based on this test, foods are typically classified into three categories.

Using the Glycemic Index is a tool, not a strict diet. It provides information about one aspect of a food: how it affects your blood sugar. It's a helpful guide for making more informed carbohydrate choices.