The Glycemic Index âor GI, for shortâis a system that ranks foods by how they affect your blood sugar levels. Low-glycemic index foods (less than 55) produce a gradual rise in blood sugar levels that's easy on the body.Foods between 55 and 70 are intermediate-glycemic index foods.Foods with high-glycemic index numbers (more than 70) make blood sugar levels as well as insulin levels spike fast. We now realize that's a health threat.oods between 55 and 70 are intermediate-glycemic index foods. Foods with high-glycemic index numbers (more than 70) make blood sugar levels as well as insulin levels spike fast.