Over the past century life expectancy in developed countries has risen dramatically, with most people living well into their 80s and many more living past 100. Many improvements over the years have enabled this overall increase in lifespan, such as major improvements in sanitation (water quality and sewage disposal), the much more effective control of common infections, and much better healthcare facilities than were available to previous generations.
Despite these advances, there is a distinct possibility that average lifespan in developed countries may start to decrease, due to the trappings of modern lifestyles, which impact the amount of physical activity we are doing and how we now consume food. This lifestyle is the main reason why we now have an obesity epidemic on our hands - one that, to date, all of the resources of medical science has not been able to fight.
Obesity brings with it an increased likelihood of a whole range of diseases, almost all of which can contribute to a premature death - it is an unfortunate statistic that people who are obese are at much greater risk of dying prematurely than people of normal weight. The terrible truth is that obesity is totally preventable with the right approach.