The 𝐠𝐥𝐲𝐜𝐞𝐦𝐢𝐜 𝐢𝐧𝐝𝐞𝐱 (GI) assigns a numeric score to a food based on how drastically it makes your blood sugar rise. Foods are ranked on a scale of 0 to 100, with pure glucose (sugar) given a value of 100. The lower a food’s glycemic index, the slower blood sugar rises after eating that food. In general, the more processed a food is, the higher its GI, and the more fiber or fat in a food, the lower it’s GI.

But the glycemic index tells just part of the story. What it doesn’t tell you is how high your blood sugar could go when you actually eat the food. To understand a food’s complete effect on blood sugar, you need to know both how quickly it makes glucose enter the bloodstream and how much glucose per serving it can deliver. A separate measure called the 𝐠𝐥𝐲𝐜𝐞𝐦𝐢𝐜 𝐥𝐨𝐚𝐝 does both — which gives you a more accurate picture of a food’s real-life impact on your blood sugar. Watermelon, for example, has a high glycemic index (80). But a serving of watermelon has so little carbohydrate that its glycemic load is only 5.