7 Ways Poor Sleep Hurts Fat Loss

7 Ways Poor Sleep Hurts Fat Loss

If you want to know why sleep is so crucial for fat loss and why sleep deprivation stalls weight loss, then you want to read this article.

When it comes to losing body fat as quickly as possible, individuals tend to focus first on reducing calories and then increasing their training intensity (usually in the form of added cardio workouts).

This 1-2 punch works incredibly well for weight loss, but after a time, weight loss slows, and that "stubborn fat" won't seem to get lost. In these instances, dieters look to reduce calories further and increase their amount of exercise. One area they never think to address, that's secretly hampering their ability to lose weight rapidly, is sleep.

Look, we get it. Sleep is one of those things that most people think is only necessary for infants and geriatrics, and the population's lack of interest in sleep is noticeable. Recent estimates suggest that adults sleep duration has decreased by 1.5-2 hours per night over the last 50 years.

And while you may not understand how or why sleep deprivation is hurting your fat loss results, it is big time.

Here, we review the various ways in which skimping on sleep handicaps your ability to lose weight quickly and easily.

So, let’s get started.

7 Ways Sleep Deprivation Hinders Fat Loss

Less Energy for Workouts

Weight loss is a matter of calories in vs. calories out. Burn more calories per day than you ingest, and you lose weight, it's a simple as that.

One of the ways to increase the number of calories you burn is through exercise.

Generally, speaking the more quality sleep you get at night, the better you can perform in your workouts. Conversely, when you sleep poorly, you're tired mentally and physically. Muscles don't respond as quickly or powerfully. You don't move as fast during cardio workouts, and you get winded that much easier when you don't get a full night's sleep.

While you can still get a workout in, it won't pack nearly the calorie burn it would have you gotten quality sleep. <7>

But that’s not all.

Not only does sleep severely impair your ability to perform at your absolute best, but it also decreases your motivation and willpower to drag yourself to the gym for your working in the first place.

Fewer calories burned in your workout, while small compared to the rest of the types of thermogenesis going on in the body, but it still count towards your total daily energy expenditure (TDEE).

And, when you’re trying to lose weight as quickly as possible, every single calorie counts.

Therefore, if you want to accomplish the greatest amount of calorie burning possible during training, you need to get a solid 8-9 hours of sleep.

Increased Hunger and Cravings

Poor sleep doesn't just affect energy output during training; it may lead you to consume more calories the next day.

The reason for this is a bit complex, but essentially, sleep deprivation disrupts the delicate balance of hormones that regulate appetite and satiety.

Leptin is the “satiety” hormone that is released by fat cells to tell the brain that you’ve had enough to eat. <1,2>

Studies have shown that chronically skimping on sleep leads to significant decreases in leptin, especially at nighttime. One study noted that after six nights of sleeping only 4 hours per night, individuals experienced a decline in leptin that was on par with where levels would be had test subjects reduced calorie intake by 900 calories per day. <3>

Here's the fascinating thing, though.

Both groups of subjects (those deprived of sleep and those getting a full night's sleep) consumed the same amount of calories and had approximately equal amounts of physical activity.

Compounding the issue is ghrelin -- the “hunger” hormone.

When individuals get less sleep, there is an increase in ghrelin secretion, particularly at night. <4> Research has also shown that individuals lacking sleep were more prone to crave sweet, carbohydrate-dense foods as well. <5>

In other words, depriving yourself of sleep makes you hungrier and more prone to eat micronutrient-poor, calorie-dense foods (e.g., junk food).

Diet is the single most crucial factor when it comes to losing fat and body recomposition. Skipping just one night of sleep can have serious ramification on your ability to stick to your diet.

Reduced Fat Burning

In addition to being more likely to overeat the day after a short night of sleep, your body also burns less fat for fuel during the day. What does it burn instead?

For the answer to that question, let’s consider a 2010 study that measured weight lost when individuals slept 8.5 hours per night and 5.5 hours per night.

Ten overweight but healthy adults had their sleep monitored for two separate 14-day periods. Additionally, every two weeks, they followed the same weight loss diet.

On both occasions (8.5 vs. 5.5 hours of sleep/night), average weight loss was about the same (~6 pounds). However, for the two weeks that Researchers found that when dieters got a full night's sleep, they lost weight consisted of a considerably higher percentage of fat. When subjects only slept an average of 5.5 hours per night, the fraction of weight lost as fat decreased by 55% and there was a 60% increase in the amount of fat-free body mass lost. <5>

In other words, while sleep deprivation may not reduce the total amount of weight you lose (provided you eat the same calories on the days you get a full night’s sleep as the ones you don’t), you lose more muscle and less body fat.

This is the exact opposite of what you want to happen when dieting as muscle retention is a primary goal of fat loss as it helps maintain a higher metabolic rate, meaning you can lose weight at a higher amount of calories.

Increased Fatigue During the Day

Not only does lack of sleep impair your ability to perform at a high level in your workouts, but it also makes you feel more tired and lazy during the day.

So, how do this general malaise and fatigue hurt your weight loss goals?

Well, when you look at the different ways, your body burns calories, one of the types of thermogenesis that's often overlooked is non-exercise activity thermogenesis (NEAT).

NEAT accounts for the energy your body uses performing all of your daily movements and activities that don’t qualify as strictly exercise. For example, activities such as doing the laundry, walking the dog, even tapping your foot while you work or watch tv counts towards NEAT.

When you don't get enough sleep, you're more likely to move less the following day (on account of being tired), which decreases the number of calories you're burning during the day, slowing the rate at which you lose weight. <7>

Increased Cortisol Levels

Cortisol is a pretty infamous hormone. It’s most often associated with stress and the creation/retention of belly fat.

Like all of our hormones, cortisol has a specific purpose and is extremely useful at times, such as when a predator is chasing you. So, in moderate doses and the right time, cortisol can help you avoid becoming lunch meat for an angry T-Rex.

However, chronically elevated levels of cortisol, like those that come with consistently depriving yourself of sleep, are terrible for fat loss and returning to healthy sleep habits.

You see, when cortisol is released, it puts our bodies into a heightened state of alertness, which is the exact opposite of what you want at night when trying to go to sleep. Research has shown that when individuals were restricted to four hours of sleep per night, their cortisol levels the following night were significantly elevated and slower to decrease than subjects who got a full night's sleep. <8>

Decreased Testosterone

Testosterone is the hormone most often associated with masculinity, manhood, and muscle growth. It's also pretty well-known that cortisol and testosterone have an inverse relationship. When cortisol is elevated, testosterone is reduced and vice versa.

For quite a while, researchers have known that sleep loss led to lower testosterone production, but the didn’t know how much lower.

A 2010 study sought to determine just how severely a poor night of sleep impacted men's testosterone levels. For seven nights (one week), ten healthy men in their 20s were restricted to five hours of sleep per night. Researchers noticed that the men's daytime testosterone levels decreased by 10-15%, and the lowest levels of testosterone were in the evening. <9>

Researchers also noted that the men had overall less energy during the week of sleep deprivation, which as we discussed impacts your workout performance and non-exercise activity thermogenesis.

Impairs Immune System Function

Your immune system is your line of defense against microscopic ne’er-do-wells that seek to plunder and pillage your cells making your ill.

Unsurprisingly, when you don’t get enough sleep, your immune system doesn’t work as well as it should.

Cytotoxic natural killer cells are a type of immune cell (antibody) that fight off antigens (toxic and foreign substances) and help repair tissue damage. However, when you regularly shortcut your sleep, the body’s immune response becomes compromised, natural killer cell activity drops, and inflammation rises. <10,11>

More specifically, levels of C-reactive protein significantly increase when you regularly skimp on sleep. In case you weren't aware C-reactive protein (CRP) is a critical inflammatory marker used by doctors to assess a person's risk of heart disease as well as get an idea of their systemic inflammation.

Being in a state of chronic inflammation leads to weight gain, reduces immune system function, and increases your risk for infection as well as other chronic diseases. <12>

Steel Dreams -- The Solution for Bad Sleep

Suffice it to say that if you want to lose weight as quickly and efficiently as possible, then you need to sleep. There's no sloughing it off until you are old and gray. Sleep impacts too many vital functions of the body as well as your ability to perform, recover and grow muscle tissue.

Due to the grave importance sleep plays in health, longevity, and your ability to be a badass in the gym, SteelFit has created Steel Dreams.

Steel Dreams is an all-natural, non-habit forming, sleep and recovery aid scientifically formulated to help reduce stress, quiet an overactive mind, and improve sleep quality and duration.

Sleep is critical, plain and simple, and Steel Dreams was created to help you get the most out of every minute of sleep every night so that you can perform at your best mentally and physically day after day.


  1. "The Impact of Sleep Deprivation on Hormones and Metabolism." Medscape, 28 Apr. 2005,
  2. Margetic, S., et al. "Leptin: a review of its peripheral actions and interactions." International Journal of Obesity, vol. 26, no. 11, 2002, pp. 1407-1433.
  3. Spiegel K, Leproult R, L'Hermite-Baleriaux M, et al. Leptin levels are dependent on sleep duration: relationships with sympatho-vagal balance, carbohydrate regulation, cortisol and TSH. J Clin Endocrinol Metab. 2004;89:5762-5771.
  4. SCHMID, SEBASTIAN M., et al. "A single night of sleep deprivation increases ghrelin levels and feelings of hunger in normal-weight healthy men." Journal of Sleep Research, vol. 17, no. 3, 2008, pp. 331-334.
  5. Greer SM, Goldstein AN, Walker MP. The impact of sleep deprivation on food desire in the human brain. Nat Commun. 2013;4:2259.
  6. Nedeltcheva AV, Kilkus JM, Imperial J, Schoeller DA, Penev PD. Insufficient sleep undermines dietary efforts to reduce adiposity. Ann Intern Med. 2010;153(7):435-41.
  7. Knutson KL, Spiegel K, Penev P, Van Cauter E. The metabolic consequences of sleep deprivation. Sleep Med Rev. 2007;11(3):163-78.
  8. Leproult, R., Copinschi, G., Buxton, O., & Van Cauter, E. (1997). Sleep loss results in an elevation of cortisol levels the next evening. Sleep, 20(10), 865–870.
  9. Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011;305(21):2173-4.
  10. Irwin, M., et al. "Partial night sleep deprivation reduces natural killer and cellular immune responses in humans." The FASEB Journal, vol. 10, no. 5, 1996, pp. 643-653.
  11. Irwin, M., et al. "Partial sleep deprivation reduces natural killer cell activity in humans." Psychosomatic Medicine, vol. 56, no. 6, 1994, pp. 493-498.
  12. Pahwa R, Jialal I. Chronic Inflammation. . In: StatPearls . Treasure Island (FL): StatPearls Publishing; 2018 Jan-.

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