In this excerpt of her new book, Arianna Huffington explains how getting enough rest is a must—for long-term health, yes, but also for keeping the weight off, doing well at work and even for better skin.

It is industrialization, for all its benefits, that has exacerbated our flawed relationship with sleep on such a massive scale.

We sacrifice sleep in the name of productivity, but ironically, our loss of sleep, despite the extra hours we put in at work, adds up to more than eleven days of lost productivity per year per worker, or about $2,280. This results in a total annual cost of sleep deprivation to the US economy of more than $63 billion, in the form of absenteeism and presenteeism (when employees are present at work physically but not really mentally focused). "Americans are not missing work because of insomnia," said Harvard Medical School professor Ronald C. Kessler. "They are still going to their jobs, but they're accomplishing less because they're tired. In an information-based economy, it's difficult to find a condition that has a greater effect on productivity.

Sleep disorders cost Australia more than $5 billion a year in health care and indirect costs. And "reduction in life quality" added costs equivalent to a whopping $31.4 billion a year. A report, aptly titled "Re-Awakening Australia," linked lack of sleep with lost productivity and driving and workplace accidents. In the United Kingdom, a survey showed that one in five employees had recently missed work or come in late because of sleep deprivation. The researchers estimated that this is equivalent to a loss of more than 47 million hours of work per year, or a £453 million loss in productivity. And almost a third of all UK employees reported feeling tired every morning. Yet, though awareness is spreading, few companies have given sleep the priority it deserves, considering its effects on their bottom line. In Canada, 26 percent of the workforce reported having called in sick because of sleep deprivation. And nearly two-thirds of Canadian adults report feeling tired "most of the time."

It turns out that women need more sleep than men, so the lack of sleep has even more negative mental and physical effects on them. Duke Medical Center researchers found that women are at a greater risk for heart disease, Type 2 diabetes, and depression. "We found that for women, poor sleep is strongly associated with high levels of psychological distress, and greater feelings of hostility, depression and anger," said Edward Suarez, the lead author of the study. "In contrast, these feelings were not associated with the same degree of sleep disruption in men."

As women have entered the workplace—a workplace created in large measure by men, which uses our willingness to work long hours until we ultimately burn out as a proxy for commitment and dedication—they are still stuck with the heavy lifting when it comes to housework. The upshot is that women end up making even more withdrawals from their sleep bank.

"Let's face it, women today are tired. Done. Cooked. Fried," wrote Karen Brody, founder of the meditation program Bold Tranquility. "I coach busy women and this is what they tell me all the time: 'I spent years getting educated and now I don't have any energy to work.' "

Just as sleep is universal, so is the belief that we don't have enough time to get the sleep we need. But we actually have far more discretionary time than we realize. The key is taking an honest look at how we spend it. In her discretionary time, for example, Sherry Turkle, professor of the Social Studies of Science and Technology at MIT, has been using TV as a reward, letting herself watch shows such as Mad Men, Homeland, and The Americans after working on her book. "I felt like I earned these elegant treats," she told me. "I remember saying 'Orange Is the New Black is mine' after I finished the 'Friendship' chapter of Reclaiming Conversation. As I worked on the 'Romance' chapter, it was House of Cards. I wouldn't have said, 'I'm prioritizing television drama,' but what strikes me is that I never said, 'I'm prioritizing sleep.' "

That's the case for millions of people around the world, despite how high the costs of sleep deprivation are. The incidence of death from all causes goes up by 15 percent when we sleep five hours or less per night. A 2015 CNN.com article based on the latest findings by the American Academy of Sleep Medicine, provocatively titled "Sleep or Die," discussed the connection between lack of sleep and an increased risk of heart attack, stroke, diabetes, and obesity. In other words, getting enough sleep really is a matter of life and death.

And even when it doesn't kill us, sleep deprivation makes us dangerously less healthy. Dr. Carol Ash, the director of sleep medicine at Meridian Health, points out that even losing an hour of sleep per week—which many of us do without a moment's thought—can lead to a higher risk of heart attack. Even the switch to daylight saving time can temporarily disturb our sleep patterns.

A lack of sleep also has a major impact on our ability to regulate our weight. In a study by the Mayo Clinic, sleep-restricted subjects gained more weight than their well-rested counterparts over the course of a week, consuming an average of 559 extra calories a day. People who get six hours of sleep per night are 23 percent more likely to be overweight. Get less than four hours of sleep per night and the increased likelihood of being overweight climbs to a staggering 73 percent. That is due in part to the fact that people who get more sleep produce less of a hormone called ghrelin—the "hunger hormone," which increases our appetite. The sleep-deprived group also had lower levels of the hormone leptin, the "satiety hormone," which lowers our appetite. In other words, cutting back on sleep is a fantastic way to gain weight. Other research points to the role of sleep in the production of orexin, a neurotransmitter that normally stimulates physical activity and energy expenditure but is reduced when you are sleep-deprived.

The bottom line? When we're not well rested, we're not as healthy. And it shows. In a Swedish study, untrained participants were asked to look at photos of both sleep-deprived and well-rested people. Participants judged those in the sleep-deprived group as "less healthy, more tired, and less attractive." An experiment in the United Kingdom tested the effects of sleep deprivation on a group of thirty women. Their skin was analyzed and photographed after they slept for eight hours and then again after sleeping six hours for five nights in a row. Fine lines and wrinkles increased by 45 percent, blemishes went up by 13 percent, and redness increased by 8 percent. In other words, we wear our lack of sleep on our faces.

The Sleep Revolution, $35, by Arianna Huffington.