You might recall the identification of klotho as a longevity-related gene in mice and other lower animals in recent years. Here is a study on levels of klotho in humans: "The aging-suppressor gene klotho encodes a single-pass transmembrane protein that in mice is known to extend life span when overexpressed and resemble accelerated aging when expression is disrupted. It is not known whether there is a relationship between plasma levels of secreted klotho protein and longevity in humans. ... We measured plasma klotho in 804 adults, greater than or equal to 65 years, in the InCHIANTI study, a longitudinal population-based study of aging in Tuscany, Italy. ... During 6 years of follow-up, 194 (24.1%) of the participants died. In a multivariate Cox proportional hazards model, adjusting for age, sex, education, body mass index, physical activity, total cholesterol, high-density lipoprotein cholesterol, cognition, 25-hydroxyvitamin D, parathyroid hormone, serum calcium, mean arterial pressure, and chronic diseases, participants in the lowest tertile of plasma klotho [had] an increased risk of death compared with participants in the highest tertile of plasma klotho ... In older community-dwelling adults, plasma klotho is an independent predictor of all-cause mortality. Further studies are needed to elucidate the potential biological mechanisms by which circulating klotho could affect longevity in humans." Given the number of adjustments there, I'd like to see a confirming study - and for preference one that explicitly took into account calorie intake as well. Just because you see the expected result is no reason to abandon the usual level of caution needed when reading the output of the scientific method.

Link: http://www.ncbi.nlm.nih.gov/pubmed/21474560