https://www.mayoclinic.org/symptoms/unexplained-weight-loss/basics/causes/sym-20050700

With change in life style the trend of consuming fast processed food has risen a lot. People have also adopted job trends that require sitting in front of screens for long periods of time. This has led to obesity as a common condition. People try to loose weight through different exercises and diets. Pathologically weight loss can be divided into 2 types of reasons. The difference is when appetite is maintained or suppressed. The conditions in which appetite is maintained include: diabetes mellitus, hyperthyroidism, malabsorption and pheochromocytoma. Conditions in which appetite is suppressed: a malignancy, respiratory failure, cardiac failure, depression and HIV.