Intermittent Fasting
Today, humans spend most of their time feeding, with
little time spent in a fasted state. We typically eat from the
moment we wake up to the moment we go to sleep. This,
however, was not the case for most of human history. Long
before religion or diet books made calorie deprivation a
carefully considered choice, our preagricultural ancestors
regularly experienced fasting as a consequence of an
unpredictable food supply. Their brains (and those we
inherited) were forged in this uncertainty and are elegantly
adapted to oscillate between the fed and fasted states as a
result.
By periodically restricting our food intake, we force
physiological adaptation and the production of ketones.
There are many different fasting protocols that one may
choose to employ. By ensuring a sixteen-hour window has
passed since your last ingested calorie, you are practicing
the common “16:8” method of fasting (which entails sixteen
hours of fasting and eight hours of allowed feeding). This
can be done daily and confers many of the benefits of
fasting, namely reducing insulin and promoting the
breakdown of stored fats. (We usually recommend women
start with twelve to fourteen hours rather than sixteen.
Women’s hormone systems may be more sensitive to
signals of food scarcity. For example, extended fasts may
negatively affect fertility.)
One way to achieve a fast of twelve to sixteen hours may
be simply skipping breakfast, a nonessential meal despite
what cereal companies will tell you. Extending the fast that
you endure every night while sleeping also makes use of the