Sleep’s profound impact on fat loss

written by Philip Stefanov  |  JULY 13, 2021

It’s ironic how we sacrifice our sleep for other, seemingly more important things. Work, play, it doesn’t matter. We put off sleep for as long as we can, lying to ourselves that, “I can get by on six hours just fine.” Of course, we always regret it in the morning and tell ourselves we’ll go to bed earlier.

But besides the many profound effects of sleep, it also impacts something dear to the hearts of many people - fat loss. And the interesting part? As little as two hours of sleep can make a huge difference.

In a study from 2010, researchers examined the effects of two sleep durations on fat loss over two weeks. Subjects were ten overweight but otherwise healthy individuals between the ages of 35 and 49. The idea was simple:

Place the subjects on a low-calorie diet (90 percent of resting metabolic rate, which is quite low) for two weeks and have them spent 8.5 or 5.5 hours in bed each night.

On average, subjects consumed about 1,450 calories per day - around 700 calories below their maintenance. The macronutrient split was 48 percent carbs, 34 percent fats, and only 18 percent protein. This comes out to only 65 grams of protein per day, which is quite low for anyone. They also had their meals weighted to ensure accuracy with the food intake.

When subjects spent 8.5 hours in bed, they slept around 7 hours and 25 minutes. When they could only spend 5.5 hours in bed, they slept around 5 hours and 14 minutes. Meaning, they fell asleep more quickly in the deprived state, which is normal.

So far, so good. Now, the results:

Subjects lost roughly 6.6 pounds in two weeks during both conditions. When they slept for over seven hours, they saw a respectable 50:50 loss of lean and fat tissue. Of course, given the aggressive deficit and low protein intake.

When they slept just over five hours, they lost fat and muscle at a 20:80 ratio. Meaning, only a fifth of the weight loss came from actual fat. And keep in mind that sleep duration was the only thing that was different in both conditions. Sleep deprivation alone led to significantly higher lean mass loss. Subjects also reported higher hunger and ghrelin levels while sleep-deprived, which, let’s face it, makes dieting suck even more.

Of course, we have a couple of caveats here:

First, subjects didn’t do any physical activity, and we know how valuable resistance training is for preserving lean tissue while dieting. Had they lifted some weights, things could have looked different. Second, while the diet only lasted for a couple of weeks, they had very little protein and a massive calorie deficit—both of these increase the risk of muscle loss.

But given that both conditions were identical, this study illustrates the importance of getting enough sleep for optimizing fat loss.

So, what’s the bottom line here?

If you’re looking to lose fat and maintain your hard-earned muscle, maintain a moderate deficit, get more protein, do some resistance training, and get at least seven hours of sleep per night.

Until next week,


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