A Sydney research team conducted a 12-week study of 129 overweight and obese people an average of 32 years old, with an average BMI of 31.2. The researchers split the subjects into four groups and randomly assigned each group a diet to follow. The first group followed a high-carbohydrate, high-glycemic diet with average protein intake. The second group followed a high-carbohydrate, low-glycemic diet with average protein intake. The third group followed a high-protein, high-glycemic diet with low carbohydrate intake. The fourth group followed a high-protein, low-glycemic diet with low carbohydrate intake.
Researchers measured each group's levels of glucose, insulin, leptin, total cholesterol, HDL "good" cholesterol and triglycerides at the start, middle and end of the study, and found that the third group had the highest percentage of people with five percent weight loss or more. However, the third diet group also experienced an increase in total and "bad" LDL cholesterol levels.
Dieters in group two (high-carb, low-GI, average protein) saw a reduction in total and LDL cholesterol. Women and participants with high triglycerides benefited the most from following the second group's diet.
"Diets based on low-GI whole grain products (instead of high-GI whole grains) maximize cardiovascular risk reduction, particularly if protein intake is high," the researchers concluded.
Researchers have debated for some time whether or not the glycemic index could be an effective tool for consumers seeking to become healthier.