Its managed holistically n need to consult ayurveda by bit detox n Rasayan ,consider to exercise in way of traditional dance form

Obese, thyroid, diabetes can cause that... If u have take treatment accordingly

It is known as acanthosis nigricans. Many a person have it as hereditary and many because of improper diet and weight gain, To prevent further worsening maintain strict diet (avoid bakery products, sweets and colddrinks) Daily exercise which leads to active sweating For clearance of present consult near by qualified dermatologist.. Within 2-3 months you can expect good results