Obesity is a global public health problem affecting about one-third of the world’s population in recent years. Overweight can be a risk factor for the majority of noncommunicable diseases and also affects the course of illness in some conditions like infectious diseases. Overweight is defined as a body mass index (BMI) of 25.0–29.9, and obesity is BMI greater than or equal to 30. Being overweight impacts diseases like diabetes mellitus, hypertension, cancer, and infectious diseases, and increases the mortality. This chapter summarizes the epidemiology, influence of obesity on public health, and the pathogenesis of obesity in various disease conditions. The impact of overweight and obesity on reproductive health especially in polycystic ovarian disease is discussed in detail. The chapter also discusses the link between the obesity and cardiovascular disease, hypertension, cancer, infectious disease, finally adding up to the management strategies of the condition.