Sleep & Body Fat


You know by now, I hope, that skimping on sleep can harm your health. You should know it can thwart your weight loss efforts; more accurately, your fat-loss efforts. Your body does incredible things while you sleep–which I’ve covered before here. When you don’t get enough quality and quantity sleep, you miss out on these benefits to varying degrees. In terms of body composition, these benefits include proper functioning of: areas of the brain that aid in decision making and affect cravings for certain types of food, and certain hormones that help regulate appetite and stabilize blood sugar levels.


Specifically, leptin, ghrelin and insulin. Don’t worry, I’ll keep it as simple as possible.
Leptin is mainly secreted by your fat cells. It decreases your hunger. The amount of leptin is
usually high when we have a lot of body fat or a lot of food (energy) coming in, because this
signals to our brain that we’re consuming enough to meet our needs. Basically, it’s telling your
brain it doesn’t need to feel hungry anymore. Insulin and blood glucose (sugar) can trigger leptin

Ghrelin is secreted in a few places in your body, but mostly in your stomach. It increases your
hunger and is generally released when you don’t have enough food (energy) coming in. Think
fasting or restrictive diets. It’s telling your brain, um hello, “feed me!!”.
Insulin, you’ve probably heard of. It plays a major role in processing the food and drink we
consume and in keeping our blood sugar levels stable. You can think of proper insulin
functioning like a piggy bank:

You put coins into a piggy bank. When the amount in the piggy bank reaches a certain level,
you empty the piggy bank into your pocket in order to spend it. When you eat, the food is broken
up and the sugars (coins) go into your bloodstream (piggy bank). When the amount of sugar in
the blood stream reaches a certain level, insulin swoops in (perhaps the hammer for the piggy
bank) and helps you empty the sugar out of the piggy bank and into your pockets (certain cells
in the body) so that the cells can spend the sugar for energy.

Highly simplified, but hopefully that helps. Ok, now that we know what’s what, we can explore
how lack of sleep messes all this up. To put it very simply: too little sleep can decrease leptin,
increase ghrelin, and increase insulin resistance. It can also affect leptin resistance.

This means you feel hungrier than you would be had you gotten your full 8-9 hours. And, as we
will discuss in a minute, you’re likely going to crave high-calorie foods (donuts, cookies,
pizza…basically junk foods). This leads to more sugar in your blood stream, which leads to more
insulin released. This can lead to weight gain to the point of obesity and a number of other
health problems related to excess body fat. It can also, as I said, lead to insulin resistance and
type 2 diabetes.

If you become insulin resistant, your cells won’t respond properly to all that insulin, leaving the
sugar in your bloodstream. To throw another log on the fire, you can also become leptin

One way this happens is from too much body fat (e.g. obesity). Like everything with our body,
there’s a sweet spot. Too much body fat appears to hinder, even halt, our body’s ability to
properly respond to leptin’s signals. We don’t feel full like we should, and so keep eating. Bad

To recap: you skimped on sleep for a few days or more, and your body’s signals got all messed
up, throwing off your appetite regulation and how your body processes sugars in foods and
drinks. A few weeks later and you’re wondering why you feel crappy and put on a few pounds.
But it doesn’t have to be weeks or months, even just a few days in a row of reduced sleep can
have ill effects.

One study published in 2012 in the Annals of Internal Medicine found total body insulin
resistance was reduced 16 percent after just four days of reduced sleep. That’s a big deal.
Another study, published in PLOS Medicine December 2004, showed that those sleeping 5
hours versus 8 hours experienced negative changes in leptin and ghrelin, and strikingly showed
that for those sleeping less than 8 hours, an increased BMI was proportional to decreased

To Eat Cookies or Workout…?

Whew! Glad that whole hormone discussion is over! Complicated stuff…If you’re not convinced, or not ready for a nap, yet, let’s look at two more ways sleep loss can affect your body composition and consequently your health.

Poor sleep impairs your ability to make strong choices by decreasing activity in your frontal lobe (complex-decision making zone of your brain) and increasing activity in your amygdala (reward zone of your brain). Again, to keep it super simple, this results in increased cravings of high-calorie foods, like sugary treats and greasy pizza and the like, and a decreased ability to decide to pass on a first, second or third helping of these “rewarding” foods or beverages. You want the bad stuff. And in today’s world, the bad stuff is increasingly in your face and easy to access.

Combine the increased cravings with the increased access with the increased hunger (discussed previously) with the decreased ability to make important decisions, and bam. The next thing you know, you’re halfway through a package of cookies and a large pizza, washing it down with a large soda. Oh, and you skipped your workout because you were too tired as a result of not sleeping well. You can see how all of this is a perfect storm; again, all of this can start to occur after just a few days in a row of insufficient sleep.

So What to Do?

Sleep. Obviously. Of course it is easier said than done. Do your best to implement good sleep habits, picking one or two at a time to start with and gradually improving on each small success.

These good habits include:

  • Unplugging from electronic devices (particularly those with blue light) at least 1 hour before bed.
  • Creating a bedtime ritual. Sleeping in a cool, dark place. Sticking to a consistent sleep schedule, as much as possible.
  • Avoiding heavy meals before bed.
  • Stopping caffeine intake 3-6 hours before bed, as caffeine can stay in your system for just as long.
  • Alcohol can also disrupt sleep for some.

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