How Sleep Loss Impacts Physical Health: Metabolism, Hormones & Accelerated Aging

Sleep loss can rapidly impair basic bodily functions to a surprising extent

Physical health is kinda like the Holy Grail of our times - everyone’s on some kind of health quest.

So what does the internet and media tell us we need for our quest? Got the exercise program? Check. Got the diet plan? Check. All good to go then? 

Not so fast. 

Science is increasingly showing that sleep is fundamental to physical health. And a study from the University of Chicago has highlighted just how quickly poor sleep can turn a dashing young Sir Lancelot into the physical health equivalent of a haggard old crone (politically correct disclaimer: some of my best friends are haggard old crones). 

Researchers studied 11 healthy young men for 16 consecutive nights to look at the physical health effects of sleep loss on basic bodily functions, such regulating blood-sugar levels, storing energy from food, and producing various hormones.

The young men all received identical diets, but sleep schedules varied:

• On the first three nights the subjects were allowed to sleep for eight hours, 11 p.m. to 7 a.m. 

• The next six nights they slept four hours, 1 a.m. to 5 a.m. 

• The following seven nights they spent 12 hours in bed, 9 a.m. to 9 p.m. 

The researchers monitored heart rate, glucose and hormone levels throughout the study. 

What did the study find?

How Sleep Loss Affects Blood Sugar Levels

• Sleep deprivation resulted in profound changes in glucose metabolism (in some situations changes resembled patients with type-2 diabetes);

• When most sleep deprived, subjects took 40% longer than normal to regulate their blood sugar levels after a high-carbohydrate meal; and

• 30% reduction in ability to secrete insulin and to respond to insulin.

How Sleep Loss Affects Hormones

Sleep loss also changed the production and action of other hormones: 

• Subjects showed decreased secretion of thyroid stimulating hormone; and

• Increased levels of the stress hormone cortisol, especially during the afternoon and evening, similar to levels seen in much older people.

Worryingly, the elevated cortisol levels are thought to contribute age-related health problems such as insulin resistance and memory impairment.

Study author Professor Eve Van Cauter, explained:

"Under sleep debt conditions, our young lean subjects…responded to a morning glucose tolerance test in a manner consistent with current diagnostic criteria for impaired glucose tolerance," 

(That’s geek speak for “subjects showed early markers of diabetes”).

She continued:

"We found that the metabolic and endocrine changes resulting from a significant sleep debt mimic many of the hallmarks of aging….We suspect that chronic sleep loss may not only hasten the onset but could also increase the severity of age-related ailments such as diabetes, hypertension, obesity and memory loss”.

That’s pretty doom and gloom for those of us with sleep problems and sleep loss. So how about the good news? 

All the changes quickly resolved after the 12 hours of recovery sleep. 

So the takeaway from all this? 

Well, do your exercise program and your diet plan, but if you want the most gains, don’t forget the importance of sleep to physical health. 

Here’s other ways in which lack of sleep can impact you physically, and emotionally and cognitively.

The study was published in the journal Lancet (Spiegel et al, 1999).