In recent years, the incidence of simple obesity in children has been increasing, and obesity poses a serious threat to children’s health and is also an important risk factor for the development of adult obesity, diabetes, atherosclerosis and other diseases. Studies have shown that simple obese children are often associated with hyperinsulinemia and hyperlipidemia. Insulin resistance in obese children is 38.7%, and their visceral fat accumulation is an independent risk factor for insulin sensitivity. Some studies have shown that insulin secretion function is normal in the basal state in children with simple obesity, and pancreatic β-cells have sufficient capacity to maintain blood glucose levels through compensatory insulin secretion. This stage is classified as the insulin compensatory stage, in which the amount of pancreatic beta cells is normal or slightly increased. The maintenance of postprandial blood glucose depends on the rapid release of insulin and sufficient sensitivity of the liver and muscles to insulin. Because insulin resistance exists in obesity, the stability of postprandial blood glucose in obese children depends on the rapid release of insulin. Studies have confirmed that in the evolution of most diabetes from normal glucose tolerance to diabetes, it is preceded by an increase in postprandial blood glucose. It indicates that despite the compensatory increase in insulin secretion in the early and second phase after glucose load to maintain blood glucose in the normal range, there are already differences compared with normal individuals and there are abnormalities in the function of postprandial insulin secretion in obese children. In conclusion, obese children not only have peripheral insulin resistance, but also have abnormal postprandial islet β-cell secretion function, which is a potential risk group for the development of type 2 diabetes. Therefore, obese children should be tested and evaluated for islet function as early as possible, and appropriate interventions should be taken. Studies have found that obese children start to gain weight at the age of 1 to 2 years old during early childhood and at the age of 10 years old during pre-puberty. Therefore, for children with a family history of obesity and children at high risk of obesity in infancy, behavioral interventions should be strengthened to prevent the onset of obesity in children to adults, thus preventing the immediate and long-term risks of obesity in children.