Since the 18th C, human life spans have increased globally from a life expectancy at birth (LE0) of 25-40y, to over 80y in healthy countries; the LE70 has also more than doubled. ... These remarkable changes are attributable to reduced loads of infections from public health and improved nutrition, starting long before immunization and antibiotics. Reduced inflammatory and infections loads are hypothesized to retard a broad suite of age-related degenerative conditions. Even brief exposure to infections in a well nourished population can have long-term consequences, as illustrated by the 1918 Influenza which increased later-life heart disease by 25% in the cohort that was prenatally exposed.
The historical improvements in life expectancy that accompany lower levels of chronic disease are an excellent illustration of aging as an accumulation of damage - that data fits well with the application of reliability theory to aging, for example. Find a way to reduce exposure to damage at the level of cells and molecular machinery and life will lengthen.
Researchers like Finch - epidemiologist S. Jay Olshansky being another with similar views - see the most plausible future as an extension of this gradual improvement from the past. It won't be the same processes at work, because the easy gains accruing from control over infectious disease have been achieved, but it will be another gradual shifting of the chart of life expectancy, just a little progress achieved with each passing year of modestly longer lives. In this view of the world, growing levels of obesity form a very serious threat that may reduce life expectancy by causing more harm than incremental medical progress will prevent.
This sort of viewpoint is, I think, harmful to the prospects for significant advances to arise from initiatives like the Strategies for Engineered Negligible Senescence. When gradualism is institutionally entrenched, radical investigations with radical goals are discouraged at every level, from student education through to the funding rat race, and cautious predictions in public do not attract the sort of supporters and researchers who can make bold strides. This is why we need philanthropists willing to back those who can credibly think outside the box and shoot for the moon. Big risks and potentially very large payoffs. In this time of revolution and progress in biotechnology, when better to break out of the straightjacket vision of incremental progress and tinkering with metabolism?