You’ve probably seen the magazine articles or news blurbs thatsay, “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 sleep deprivation did “cause” fat gain, 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. So how does it really work? Why do you tend to gain body fat when you are sleep deprived?…

Almost all the research on this subject has been cross sectional and therefore does not prove causality. Research suggests that the likely explanation is a disruption in hormones which can affect appetite and foodintake so you are more likely to eat more when you are sleep deprived.

For example, a new study published in the December 2007 issueof “Nutrition Research Reviews” says that sleep deprivation canreduce leptin (the anti starvation hormone, also known as ananorexigenic hormone) and increase ghrelin, a stomachhormone that increases hunger.

This makes total sense – think about it: less sleep equalsmore awake time. more awake time equals greater energy needs.Greater energy needs can be satisfied by increasing appetitestimulating hormones. Leptin is an appetite stimulating hormone.

The human body is incredible and amazingly self-regulating, isnt it?

In addition, when hormones are out of balance, that can affectnutrient paritioning.

Nutrient paritioning refers to where the energy comes from whenyou have a calorie deficit – fat or lean tissue – and where theenergy goes when you are in a calorie surplus – fat or lean tissue.

So, when partitioning hormones are messed up due to sleepdeprivation, it’s entirely possibly that you are more likely toadd fat when in a surplus (not muscle) and lose muscle (not fat)when in a deficit.

This is similar to what happens during stress. Stress alsodoes not “cause” fat gain, but it certainly correlates tofat gain, for the same reasons. Imagine what happens whenyou are stressed AND sleep deprived?

Some people seem to get by with less sleep than others. I knowmany people, myself included, who excel physically on 6-7 hoursa night, so there is certainly a variation in sleep needs fromperson to person.

Developing sleep habits that promote deep, high quality sleepmay also reduce sleep needs an hour or two. This includes goingto bed and waking up at the same time every night, getting tosleep early and awake early to maximize night time sleeping hoursand daylight waking hours, sleeping in a dark room, avoidingalcohol and stimulants prior to bedtime, reducing stress andexercising regularly.

However, in light of past research and the new data that was justpublished, if in doubt, it’s surely better to err on the side ofa little more sleep than a little less sleep.

Train hard and expect success,

Tom Venuto,
Author of Burn The Fat, Feed The Muscle

PS What has your experience been regarding how much sleepyou need compared to other people you know and how have various amounts of sleep affected your fitness and body fat results? Share your comments by posting on the blog below

Scientific Reference:

The influence of sleep and sleep loss upon food intake andmetabolism. Nutrition Research Reviews, , 20:195-212,Cibele Aparecida Crispima, et al. Federal University of Sao Paulo, Brazil


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