Every once in a while, I come across something in the diet/nutrition/fitness/lifestyle arena that I’ve never even heard of before.

The following passage from Mark Sisson‘s book The Keto Reset Diet is one of them.

And since I’m currently focusing on an extremely low-carb/keto diet, and am actively avoiding anything that causes increased insulin (sugar, carbs, hidden sugars/sweeteners, and even artificial sweeteners like aspartame), in the interest of reducing insulin resistance and becoming fat-adapted instead of sugar/carb dependent, I thought this passage to be a profoundly important addition to this effort, and wanted to share it with everyone:


“While we all understand the importance of good sleep and we pay plenty of lip service to the subject, the reality is that sleep is getting the shaft in high-tech modern life. While I offer an assortment of tips and techniques for optimizing your sleep in this section, the essence of the problem is this: excess artificial light in digital stimulation after dark. Our delicate circadian hormonal processes have been synchronized with the rising and setting of the sun for millions of years. When the sun sets, humans are hardwired to wind down, start to feel sleepy in a few hours, and gracefully transition to a fully restorative night of sleep. Many sleep experts believe we also may be hardwired for biphasic sleeping habits, such that a midday nap is the default human expectation for hormone optimization.

Today, instead of experiencing a mellow and graceful transition to sleepiness during the evening hours, our exposure to artificial light after sunset kicks off a chain reaction of adverse hormonal events. Artificial light and digital stimulation after dark suppress the release of melatonin, the hormone that makes us feel sleepy in the evening (a process known as dim light melatonin onset, or DLMO). In tandem, we experience a spike in the primary stress hormone cortisol. Initially, cortisol floods the bloodstream with glucose, giving us a “second wind” to stay awake and finish our emails or Netflix series binge. Thus, if you stress yourself in this manner every night, chronically elevated evening cortisol can bind with the appetite receptors in the brain and trigger you to consume high-calorie foods. Late nights also dysregulate ghrelin (spiking appetite) and leptin (promoting fat storage). Indeed, our digestive systems also have a circadian rhythm, and eating late at night can mess things up (details in the appendix), making it likely that you’ll eat beyond feeling satisfied and store those calories as fat.

From a genetic perspective, your artificially lengthened days have tricked your genes into thinking it’s summer all the time. During the long, bright days of summer, we became hardwired over 2.5 million years of evolution to consume extra carbs (i.e., ripe fruit) and to store those calories as fat—to prepare for the long winters of food scarcity. It may be hard to believe, but your innocent use of the computer, television, or smart phone has a profound effect in locking you into fat-storage patterns. When nights of digital stimulation and insufficient sleep are a fixture in your life, you can become insulin resistant, meaning you are more likely to store your midnight snacks as fat, and more likely to crave sugar because you do a poor job of accessing and burning internal energy stores. One study from the university of Chicago shows that just two weeks of sleep deprivation (subjects slept for four hours per night) resulted in a 50% increase in insulin resistance!