so? Because humans are born half-baked.
When a healthy human baby emerges from the womb,
she is born physically helpless and with an underdeveloped
brain. Unlike most animals at birth, a newborn human is not
equipped with a full catalogue of instincts preinstalled. It is
estimated that if a human were to be born at a similar stage
of cognitive development to a newborn chimp, gestation
would be at least double the length (that doesn’t sound fun
—am I right, ladies?). By being born “prematurely,” human
brains complete their development not in the womb, but in
the real world, with open eyes and open ears—this is
probably why we’re so social and smart! And it is during
this period of rapid brain growth, what some refer to as the
“fourth trimester,” that our fat serves as an important ketone
reservoir for the brain, which can account for nearly 90
percent of the newborn’s metabolism.^10 Now you know:
baby fat isn’t just there for pinching. It’s there for the brain.
In the context of a “normal” Western diet that’s rich in
carbohydrates, significant ketone production is inhibited the
vast majority of the time.^11 This is because foods that are
high in carbohydrates elicit an insulin response from the
pancreas, and ketosis is brought to a grinding halt whenever
insulin is elevated. Suppression of insulin, on the other
hand, either by fasting or by eating a diet very low in
carbohydrates, drives ketogenesis. Let’s explore these two
routes to ketone creation.