Lifespan: Why We Age—and Why We Don't Have To

by David A. Sinclair

In one such study, participants ate a normal diet most of the time but turned to a significantly restricted diet consisting primarily of vegetable soup, energy bars, and supplements for five days each month. Over the course of just three months, those who maintained the “fasting mimicking” diet lost weight, reduced their body fat, and lowered their blood pressure, too. Perhaps most important, though, the participants had lower levels of a hormone made primarily in the liver called insulin-like growth factor 1, or IGF-1. Mutations in IGF-1 and the IGF-1 receptor gene are associated with lower rates of death and disease and found in abundance in females whose families tend to live past 100.