Healthy lifestyle changes including promoting healthy eating habits and increasing the level of physical activity are the first steps in the treatment of childhood obesity. However, failure to achieve the desired success with traditional approaches has led clinicians to seek new treatments. One of the most interesting approaches has been diets based on the regulation of postprandial blood glucose and insulin levels. With these diets, the concept of glycemic index (GI), which is used to evaluate the glycemic response of carbohydrate-containing foods, has come to the fore. In the studies conducted, it is suggested that low GI diets may help in the treatment of obesity by showing the relationship between GI of diets and obesity, and obtaining results that could reduce food intake and hunger feelings as well as postprandial blood glucose and insulin levels by low GI meals. On the other hand, it is confusing to know that not only carbohydrates, but also proteins and fats have a role on postprandial insulin release. Therefore, considering the GI to control postprandial glycemic and insulinemic response is inadequate, and a method of assessing the effects of proteins and fats as well as carbohydrates is needed. In order to meet this requirement, the concept of food insulin index (FII) has been developed. The positive results on postprandial insulin response and appetite are promising, while the number of studies on FII, a relatively new concept, is limited. As a result, the use of low GI and FIT diets may be beneficial in the treatment of childhood obesity. Nevertheless, there is a need for more well-planned short- and long-term studies in order to make definitive recommendations.