Adding Years to Our Life

FGF21 expression is markedly increased in response to fasting starvation. But unlike mice, which show an increase after just 6 hours of fasting, humans don't get a notable surge in FGF21 until after a week.

Circulating FGF21 levels are also increased dramatically when you eat a lower protein diet—over a 150% increase within 4 weeks.

The recommended daily allowance of protein for most men is 56 grams of protein a day, though most American men are getting over 100.

Exercise boosts FGF21 levels, which may, in fact, be one of the reasons exercise is so good for us.

FGF21 is characterized as a systemic enhancer of longevity. It can be boosted through prolonged fasting. But thankfully, there are other less drastic measures, such as more carbs or less protein.