Weight Management and Disease Prevention
Dietary replacement of saturated fats by carbohydrates with a low glycemic index may be beneficial for weight control, whereas substitution with refined, high glycemic index carbohydrates is not. A Cochrane review found that adoption of low glycemic index (or load) diets by people who are overweight or obese leads to more weight loss (and better fat control) then use of diets involving higher glycemic index/load or other strategies. Benefits were apparent even with low glycemic index/load diets that allow people to eat as much as they like. The authors of the review concluded that "Lowering the glycemic load of the diet appears to be an effective method of promoting weight loss and improving lipid profiles and can be simply incorporated into a person's lifestyle."
In clinical management of obesity, diets based on a low glycemic index/load appear to provide better glycemic and inflammatory control than ones based on a high glycemic index/load (and therefore could potentially be more effective in preventing obesity-related diseases). In overweight and obese children, adoption of low glycemic index/load diets may not lead to weight loss but might potentially provide other benefits.
Several lines of recent  scientific evidence have shown that individuals who followed a low-GI diet over many years were at a significantly lower risk for developing both type 2 diabetes, coronary heart disease, and age-related macular degeneration than others. High blood glucose levels or repeated glycemic "spikes" following a meal can promote these diseases by increasing systemic glycative stress, other oxidative stress to the vasculature, and also by the direct increase in insulin level. The glycative stress sets up a vicious cycle of systemic protein glycation, compromised protein editing capacity involving the ubiquitin proteolytic pathway and autophagic pathways, leading to enhanced accumulation of glycated and other obsolete proteins.
Postprandial hyperglycemia is a risk factor associated with diabetes. A 1998 study shows that it also presents an increased risk for atherosclerosis in the non-diabetic population and that high GI diets, high blood-sugar levels more generally, and diabetes are related to kidney disease as well.
Conversely, there are areas such as Peru and Asia where people eat high-glycemic index foods such as potatoes and high-GI rice without a high level of obesity or diabetes.The high consumption of legumes in South America and fresh fruit and vegetables in Asia likely lowers the glycemic effect in these individuals. The mixing of high- and low-GI carbohydrates produces moderate GI values.
A study from the University of Sydney in Australia suggests that having a breakfast of white bread and sugar-rich cereals, over time, can make a person susceptible to diabetes, heart disease, and even cancer.
A study published in 2007 in the American Journal of Clinical Nutrition found that age-related adult macular degeneration (AMD), which leads to blindness, is 42% higher among people with a high-GI diet, and concluded that eating a lower-GI diet would eliminate 20% of AMD cases.