If you’ve heard of the glycemic index (GI), you probably associate it with diabetes: To help keep blood sugar levels even, people with diabetes should eat foods that score low on the GI and avoid high-glycemic foods, which tend to spike levels. In fact, research shows eating too many high-GI foods raises risks not only for developing type 2 diabetes, but also inflammation, some cancers, and cardiovascular disease. High blood sugar also prompts the pancreas to pump out lots of insulin, upping blood triglyceride levels and promoting fat storage in the belly area.

“Including more low-glycemic foods in your diet can be a healthy way to lose weight, improve energy, and alleviate mood swings, especially if you have insulin resistance,” says David Edelson, MD, an obesity expert and assistant clinical professor of medicine at Albert Einstein College of Medicine in New York City. But a food’s GI value often doesn’t tell the whole story. For instance, a high-GI snack or drink can boost energy and improve performance during an intense workout. Here’s our guide to more exceptions to the GI rule, plus tips on how best to use GI values to assess foods.