In life we find that some obese people’s neck is always dirty, black, always can not be washed, sometimes in the armpits also have. This is “acanthosis nigricans”, which is a manifestation of too much insulin in the body. Diabetes is caused by insulin deficiency. However, in the early stages of diabetes and prediabetes, a large proportion of obese patients do not have low levels of insulin in their bodies, but rather high. This means that these patients do not have enough insulin in their bodies and they need more insulin to keep their blood sugar in the normal range. Excessive insulin will lead to further weight gain, increased load on the heart, brain and kidneys, elevated blood pressure, and will greatly increase the burden of insulin secretion by the pancreas. In the long run, the function of pancreatic islets will be continuously damaged, and blood vessels will also have more serious damage. One day, when the amount of insulin secreted by the pancreas is not enough to compensate for insulin resistance, the organism will be found to have diabetes. In this sense, a dark neck may be the earliest sign of diabetes. It makes sense to check and treat at this stage so as to protect the patient from entering the diabetes stage. Treatment includes lifestyle changes such as diet and exercise, and adjunctive treatment with medication. When weight loss occurs, the neck naturally clears up. Likewise, the hyperinsulinemic state is corrected and the risk of developing diabetes is gone. Relationship between obesity and acanthosis nigricans Due to metabolic abnormalities, acanthosis nigricans accounts for a large proportion of obesity in adolescents. Hyperinsulinemia, type 2 diabetes mellitus, and polycystic ovary syndrome are closely related. However, there is a lack of effective targeted treatment for this disease. The condition of the skin can be restored to improve with weight loss.