Results

Depending on your health goals, studies of the benefits of GI diets have produced mixed results.

Weight loss

Results of a 16-year study that tracked the diets of 120,000 men and women were published in 2015. Researchers found that diets with a high GL from eating refined grains, starches and sugars were associated with more weight gain.

Other studies show that a low GI diet may also promote weight loss and help maintain weight loss. However, data from another study indicated a substantial range in individual GI values for the same foods. This range of variability in GI values makes for an unreliable guide when determining food choices.

Blood glucose control

Studies show that the total amount of carbohydrate in food is generally a stronger predictor of blood glucose response than the GI. Based on the research, for most people with diabetes, the best tool for managing blood glucose is carbohydrate counting.

Some clinical studies have shown that a low-GI diet may help people with diabetes control blood glucose levels, although the observed effects may also be attributed to the low-calorie, high-fiber content of the diets prescribed in the study.

Cholesterol

Reviews of trials measuring the impact of low-GI index diets on cholesterol have shown fairly consistent evidence that such diets may help lower total cholesterol, as well as low-density lipoproteins (the "bad" cholesterol) — especially when a low-GI diet is combined with an increase in dietary fiber. Low- to moderate-GI foods such as fruits, vegetables and whole grains are generally good sources of fiber.

Appetite control

One theory about the effect of a low-GI diet is appetite control. The thinking is that high-GI food causes a rapid increase in blood glucose, a rapid insulin response and a subsequent rapid return to feeling hungry. Low-GI foods would, in turn, delay feelings of hunger. Clinical investigations of this theory have produced mixed results.

Also, if a low-GI diet suppresses appetite, the long-term effect should be that such a diet would result over the long term in people choosing to eat less and better manage their weight. The long-term clinical research does not, however, demonstrate this effect.