Glycemic Index - What Is It?

Fifty-Plus Fitness Library

Library : Year 2 | Session 4: Diet and Aging

Glycemic Index - What Is It?

Dear Dr. Bortz,

I have read about something called the glycemic index. What is it and does it provide any guidance as to the best foodstuffs to fuel an exercise habit? ___ Betty Cole, Wilmington, NC

Dear Betty,

The term glycemic index was conjured to differentiate the different forms of carbohydrate, those that are quickly and easily digested, such as simple sugars or honey, versus those, which are slowly digested like the complex starches found in grains and legumes. Nutritionists interested in diabetes actively investigated this differentiation. I have always contended that high glycemic index foods placed a much higher and more instantaneous challenge to the insulin reserves than did foods with a low glycemic index. Recent recommendations from the American Diabetes Association, however, have cast doubt on this difference, and have instead emphasized merely the total amount of carbohydrate, rather than their type.

A paper in the ACSM publication two years ago from workers in the United Kingdom looked at the effect of meals of different glycemic index on treadmill running performance. They concluded that it was the amount and not the type of carbohydrate, which determined exercise performance.