Tag Archives: sleep

Sleep and Weight Loss

While asleep our metabolic rate increases such that we lose more than three times the amount of weight than if we are awake (awake but lying dormant, of course): 1.9g/min compared to 0.6g/min.

This increase in ‘caloric expenditure’ is not yet fully understood, but there are a number of reasons why we may lose more weight while asleep than awake:

We know that in rapid eye sleep (REM), in which we spend roughly 25% of our total sleep time, the brain’s metabolic rate (the rate at which it consumes energy) is very high, even more than while awake. And while one’s body temperature drops while sleeping, during REM it increases, and this too may cause increased caloric expenditure.

This is in addition to “changes in the hormones which govern hunger and satiety, leptin and ghrelin”.

The Cognitive Importance of Good Sleep

After a week of surviving on minimal sleep you may assume that a lazy weekend will allow you to recover in time for the coming days. Not so: research has shown that not even a full week of quality sleep can reverse the cognitive and physiological ‘damage’ just five days of poor sleep can inflict on us.

Jonah Lehrer notes that it’s not just our cognitive functions that become impaired by a lack of sleep–it’s our immune system, too:

In a recent study for The Archives of Internal Medicine, scientists followed 153 men and women for two weeks, keeping track of their quality and duration of sleep. Then, during a five-day period, they quarantined the subjects and exposed them to cold viruses. Those who slept an average of fewer than seven hours a night, it turned out, were three times as likely to get sick as those who averaged at least eight hours.

Surviving Jet Lag

With my 25-hour flight from Sydney back to London fast approaching, my mind is wandering to the topic of jet lag–or desynchronosis, to use the medical term.

The most often suggested remedies for jet lag (where recovery times are generally said to be 1 day per eastward time zone or 1 day per 1.5 westward time zones) are fasting for 11-16 hours before the flight or wearing sunglasses (the latter is what the British Airways jet lag calculator is based on).

Not particularly a fan of these methods, I concur with Bryan Caplan’s advice as he frames jet lag (and infant night feedings) in terms of fixed costs:

My alternative: Do not sleep on the plane.  At all.  When you arrive, do not sleep – at all – until a locally normal bedtime.  Pay the fixed cost without cheating.  When you wake up eight to ten hours later, you will be refreshed and in sync with your new time zone.  In exchange for less than a day of sleep deprivation, you will feel fine for the rest of your trip.

This technique has served me well for many years.