The Skinny Kid

We have pointed to studies on calorie restriction before.  Believers in the process note that it works in almost all other animals, so why not humans? Obviously a true study of the effects would take decades to complete. However, a shorter study has shown that markers for longevity start getting triggered early.
Researchers Study Whether Cutting Calories May Help You Live Longer (press release)

Reducing calories over six months resulted in a decrease in fasting insulin levels and body temperature, two biomarkers of longevity, according to a study in the April 5 issue of JAMA. Longer studies are required to determine if calorie restriction changes the aging process in humans.

Prolonged calorie restriction increases life span in rodents and other shorter-lived species. Whether this occurs in humans is unknown, according to background information in the article. One theory concerning the antiaging effects of calorie restriction is its impact on metabolism, including alterations in insulin sensitivity and signaling, neuroendocrine function, stress response, or a combination of these.