The Importance Of The Glycemic Index Of A Pre-exercise Snack For Persons With Pre-diabetes: 855

As more pre-diabetic individuals embark upon an exercise programs to control blood glucose and insulin levels, it becomes increasingly important to provide them with scientifically based recommendations on pre-exercise nutrition. PURPOSE: To determine if a low glycemic index (GI) pre-exercise food provided to a pre-diabetic population results in more desirable glucose and insulin responses prior to, during, and post exercise compared to moderate and high GI foods. METHODS: Eleven male pre-diabetic subjects (age = 54.5 ± 4.4y, fasting blood glucose = 6.32 ± 0.43 mmol/L, body fat = 23.4 ± 5%) performed a VO2max test to determine the exercise intensity of the experimental trial. Using a crossover design, subjects cycled at 50% of VO2max for 45 min after consuming pre-execise feedings (30 min pre) of water or 50 grams of a low, moderate, or high GI carbohydrate. Blood samples were obtained for the determination of serum glucose and insulin prior to, during, and after exercise. RESULTS: Pre-exercise serum glucose values were significantly lower in the low GI condition (9.49 ± 1.30 mmol/L) when compared with the high GI (10.95 ± 1.99 mmol/L). Ten min into exercise, low GI (7.64 ± 2.16 mmol/L) and moderate GI (7.76 ± 2.61 mmol/L) were both lower than high GI (9.16 ± 3.02 mmol/L). This was also found 20 min into exercise (low GI = 6.15 ± 2.13 mmol/L; moderate GI = 6.53 ± 2.88 mmol/L; high GI = 7.80 ± 3.10 mmol/L). Insulin values were also decreased in the low GI trial pre-exercise and for the first 10 min of exercise when compared with both moderate and high GI. Twenty min into exercise, serum insulin for the low GI was reduced compared with the high GI, but not the moderate GI condition. CONCLUSION: Prior to and in the early phases of exercise low GI appears to be beneficial for both glucose and insulin values. Moderate GI leads to lower glucose, but not insulin values. GI was not influential upon post exercise glucose or insulin responses. This project was Supported by the California Raisin Marketing Board.