Here is a JAMA article on the epidemiological consequences of increased obesity, written from a conservative point of view - i.e. the author believes that advancing medical technology will not greatly increase life span in the foreseeable future. "In 1900, [infectious disease] was a major concern, and the most common causes of death in the United States and in many parts of the world at the time were pneumonia and tuberculosis. Today, most individuals die of cardiovascular disease or cancer. This dramatic shift in the illnesses that cause the majority of death and disability has been divided into 4 stages known as the epidemiologic transition. In the last 2 decades, however, a fifth stage, marked by an alarming increase in overweight and obesity and continued decreases in physical activity, has emerged. ... By the mid 1960s, the United States had entered the fourth stage of delayed degenerative diseases. Cardiovascular disease mortality declined, related to preventive strategies such as smoking cessation programs and effective blood pressure control, acute coronary care units, and technological advances that included coronary artery bypass surgery. Despite the many advances in preventive medicine and treatment that reduced cardiovascular disease, the new stage of the epidemiologic transition, the age of obesity and inactivity, emerged to threaten the progress made in postponing illness and death to later in adult life spans. The steady gains made in both quality of life and longevity by addressing risk factors such as smoking, hypertension, and dyslipidemia are threatened by the obesity epidemic."