Lights Out: Sleep, Sugar and Survival

In a recent podcast, paleo proponent Robb Wolf rattled off a list of books he recommended. This was mentioned.

Lights Out: Sleep, Sugar, and Survival
Lights Out: Sleep, Sugar, and Survival by T. S. Wiley is an amazing book right up until the end. Readers of this site already know that I am convinced of the evolutionary fitness and nutrition argument. Although my science background is limited (self-taught), it makes sense to me. Lights Out made a compelling case for extending the body of evolutionary health to sleep.

For much of evolution, we did not have night time light. This meant man slept more and moved less in the winter months. Food sources were more scarce in winter and strongly favored protein and fat. During the summer, days were longer and carbohydrate sources were more plentiful. Man would eat carb sources in the summer, which would spike insulin that promotes fat gain. That fat would be utilized for fuel during the winter. This is the basic concept of Summer vs Winter Mode, which NephroPal wrote about last year.

Lights Out is mostly about the evolutionary and hormonal aspects of light and sleep. Longer days (more light) tell the body via hormones that it is summer and that means “eat sugar now before winter comes“. Shorter days (less light) tell the body to sleep more and eat less. The problem is we are not only in constant Summer Mode from endless supplies of carbohydrates, we are in constant Summer Mode from excessive lighting and shortened winter sleep cycles. Winter Mode is for repair. When that repair doesn’t happen (no Winter Mode), it can result in obesity, cancer, and mental illness.

Even though it goes deep into hormonal science, I found the writing style extremely clear. Some of the reviewers on Amazon did not like the confident, know-it-all tone of the author. I loved it. I felt Lights Out did a brilliant job of digging deep into the science and then stepping back to draw focus on important points.

Before I got to the last 30 pages, I was ready to call this the book of the year. It was excellent. Then it went down a path of mixing the history of the low-fat movement with government conspiracy theories. Unlike the rest of the book, this section seemed garbled and out of place. I lost some confidence in the author. It was enough of a red flag for me to go online and do more research on the author. The results were not favorable – although I could not find anyone that had issues with the first 170 pages of Lights Out. Regardless, I am sitting here having read an amazing book where I don’t know if I can trust the source. My gut says what I learned is accurate, but I think I need to do a lot of follow-up research. The good news is winter is still months away, so I have plenty of time to discover if the Lights Out thesis has merit.


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  1. Lights Out?
    The problem with this analysis is it assumes all humans lived at the European or Seattle latitudes.
    If humans indeed originated in the neighborhood of Kenya and spent their paleo years there, winter and summer daylight hours were not like they are in northern latitudes like Seattle and Europe.
    On the equator daylight and night are each exactly 12 hours all year. So there was plenty of food of all types most of the year. Now, Eskimos and Vikings is a different story…for them in the summer they would have 18 hours or more (and further north 24 hours of daylight in summer and 24 hours of darkness in winter)
    So, when did humans develop their paleo diets? on the long trek out of Kenya and the tropics or just recently (historically speaking) in the northern latitudes?

  2. I have many of the same questions and have located another book that I hope will answer them.

    12 hours of darkness is still tremendous in the modern word. We are bathed in artificial light deep into night. This light does interfere with the release of melatonin, which has negative health consequences.

  3. The book ‘At Day’s Close: Night in Times Past” was well written, but did not cover the paleolithic era. It was mostly 1500-1900s Europe and America.

  4. can you explain what his conspiracy theories are (in brief)?

  5. @Joe – I don’t have the book in front of me, so I don’t want to misquote the author. It had to do with government propaganda unrelated to the thesis of the book. I’m not discounting it, but was completely out of place in this book.

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