You've probably seen the magazine articles or news blurbs that
say, "lack of sleep can make you fat!"
There is a lot of confusion however, about the mechanism.
It's not uncommon for people to believe there is a cause and
effect relationship between sleeping less and gaining weight.
However, if that were the case, then you would always gain weight
if you slept less even if your food intake stayed the same.
To the contrary, if you sleep less AND eat less, rest assured
you will lose weight.
If you are awake more hours and you are more active during
those increased waking hours, again, rest assured you will
lose weight.
Almost all the research on this subject has been cross sectional
and therefore does not prove causality.
Research suggests that the likely explanation for a mechanism
is a disruption in hormones which can affect appetite and food
intake so you are more likely to eat more when you are sleep deprived.
For example, a new study published in the December 2007 issue
of "Nutrition Research Reviews" says that sleep deprivation can
reduce leptin (the anti starvation hormone, also known as an
anorexigenic hormone) and increase ghrelin, a stomach
hormone that increases hunger.
This makes total sense. Think about it: less sleep equals
more awake time. More awake time equals greater energy needs.
Greater energy needs can be satisfied by increasing hunger hormones.
Leptin and ghrelin are appetite-stimulating hormones.
The human body is incredible and amazingly self-regulating, isnt it?
In addition, when hormones are out of balance, that can affect
nutrient paritioning.
Nutrient paritioning refers to where the energy comes from when
you have a calorie deficit - fat or lean tissue - and where the
energy goes when you are in a calorie surplus - fat or lean tissue.
So, when partitioning hormones are messed up due to sleep
deprivation, it's entirely possibly that you are more likely to
add fat (not muscle) when in a surplus and lose muscle (not fat)
when in a deficit.
This is similar to what happens during stress. Stress also
does not "cause" fat gain, but it certainly correlates to
fat gain, for similar reasons. Imagine what happens when
you are stressed AND sleep deprived?
Some people seem to get by with less sleep than others. I know
many people, myself included, who excel physically on 6-7 hours
a night, so there is certainly a variation in sleep needs from
person to person.
Developing sleep habits that promote deep, high quality sleep
may also reduce sleep needs an hour or two. This includes going
to bed and waking up at the same time every night, getting to
sleep early and awake early to maximize night time sleeping hours
and daylight waking hours, sleeping in a dark room, avoiding
alcohol and stimulants prior to bedtime, reducing stress and
exercising regularly.
However, in light of past research and the new data that was just
published, if in doubt, it's surely better to err on the side of
a little more sleep than a little less sleep, if more muscle and
less fat is your goal.
Reference:
1. The influence of sleep and sleep loss upon food intake and
metabolism. Nutrition Research Reviews, Dec 2007, 20:195-212,
Cibele Aparecida Crispima, et al. Federal University of Sao Paulo, Brazil
