GLYCEMIC INDEX













  • Reference [51]
GI category GI value
Low GI ≤ 55
Medium GI 56 - 69
High GI ≥ 70








OmniCarb Trial - Effect of High vs Low Glycemic Diets on CVD Risk Factors, JAMA (2014) [PubMed abstract]
  • The OmniCarb trial enrolled 163 overweight adults
Main inclusion criteria
  • ≥ 30 years old
  • SBP 120 - 159 mmHg
  • DBP 70 - 99 mmHg
  • BMI ≥ 25
Main exclusion criteria
  • Cardiovascular disease
  • Diabetes
  • Chronic kidney disease
  • Taking medication that lowers blood pressure or lipids
  • Fasting blood glucose level ≥ 125 mg/dL
Baseline characteristics
  • Average age 53 years
  • Average BMI - 32
  • Average triglycerides - 105 mg/dl
  • Average LDL - 153 mg/dl
  • Average HDL - 58 mg/dl
  • Average SBP - 132 mmHg
  • Average insulin sensitivity - 7.3
Randomized treatment groups
  • Patients crossed over between 4 different diets. Each diet was consumed for 5 weeks with a 2-week washout between diets.
    • 1. High-carbohydrate, high-glycemic index
    • 2. High-carbohydrate, low-glycemic index
    • 3. Low-carbohydrate, high-glycemic index
    • 4. Low-carbohydrate, low-glycemic index
  • Low carbohydrate = 40% of calories from carbs. High carbohydrate = 58% of calories from carbs
  • Low glycemic index = average GI ≤ 45; High glycemic index = average GI ≥ 65
  • All of the meals were prepared for the patients and they were consumed under staff supervision
  • Calorie intake was adjusted to maintain initial body weight
Primary outcome: Coprimary outcomes were insulin sensitivity (measured by Matsuda index), systolic blood pressure, low-density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, and triglyceride levels. Outcomes were measured at the end of each 5-week diet period.
Results

Duration: 5 weeks on each diet
Outcome Diet 1 Diet 2 Diet 3 Diet 4 Comparisons
Insulin sensitivity (lower numbers indicate less sensitivity) 8.9 7 7.9 8.1 1 vs 2 p≤0.01 | All other p>0.05
LDL (mg/dl) 139 146 138 138 1,3, or 4 vs 2 p≤0.01 | All other p>0.05
HDL (mg/dl) 57 57 59 58 1 vs 3 p≤0.01 | all other p>0.05
Triglycerides (mg/dl) 111 107 90 86 3 or 4 vs 1 or 2 p≤0.01 | 4 vs 3 p=0.02 | All other p>0.05
SBP (mmHg) 124 124 123 123 p>0.05 for all comparisons

Findings: In this 5-week controlled feeding study, diets with low glycemic index of dietary carbohydrate, compared with high glycemic index of dietary carbohydrate, did not result in improvements in insulin sensitivity, lipid levels, or systolic blood pressure. In the context of an overall DASH-type diet, using glycemic index to select specific foods may not improve cardiovascular risk factors or insulin resistance.