Menu

Sports Science Update: Revisiting The Glycemic Index

  • By Matt Fitzgerald
  • Published Nov 15, 2011
  • Updated Nov 16, 2011 at 11:22 AM UTC

New evidence suggests the glycemic index of foods doesn’t matter as much as you’ve been told.

Written by: Matt Fitzgerald

Twenty years ago, most Americans had never heard of the glycemic index. Today, it’s a familiar concept. We all know that the glycemic index is a measure of how quickly the blood glucose level rises after carbohydrate-containing foods are consumed. We know that most vegetables and whole-grain foods are considered low to moderate glycemic, while most sugary and starchy foods are considered high glycemic. And we know that the carbs in high-glycemic foods are more likely to be converted to body fat and that, over time, eating too many high-glycemic foods increases the risk of becoming overweight and insulin resistant.

It turns out, however, that we might not know as much about the glycemic index as we think we do. Nutrition scientists are now finding that the effect of foods on blood glucose levels may have more to do with individual biochemistry than with the foods themselves. For example, the glycemic index of white bread is 70. But in a recent study involving 14 subjects, the individual glycemic index scores of white bread ranged from 44 to 132. Sure, the average score was 70, but that score was irrelevant to most of the study participants’ bodies!

What’s more, the Tufts University Researchers who conducted this study also found a high degree of variation in the blood glucose response to specific foods within individuals depending on when they ate them—as much as 42 percent variation. That means a low-fat muffin could be a low GI food for you in the morning and a high GI food in the evening!

What does this mean for you? It means that it’s rather pointless to base your food choices based on foods’ glycemic index, which represents an average value that might not apply to you.

Next »

FILED UNDER: Nutrition

Matt Fitzgerald

Matt Fitzgerald

Sign up for our free e-newsletter, SBR Report!

Subscribe to the FREE Triathlete newsletter