please please please stop crash dieting

Sleep is more important for weight loss than Diet & Exercise
Grow Like Oak

Sleep is more important for weight loss than Diet & Exercise 

If I say the words “Weight Loss” – what comes to mind?


Indeed!  There’s another conversation that i’d like to have, though – and it’s a big one.

One of Sleep.

We’re all sold on the fact that diet and exercise are the only ways to lose weight. Calories in Calories out.  Yes, this has merit. However, there’s more to the story, and thankfully this one requires a little less work. None, in fact.

Paradoxically, one of the reasons sleep hasn’t gotten centre stage in the health and weight loss world is because there isn’t any ACTION.  We love action.

Diet and exercise – as tough as it might be – is tangible, and it requires some level of sacrifice.  Diet requires learning, prepping, and for many of us, resisting. Exercise means sweating, pushing through the burn, achieving PB’s. 

Sadly, sleep just can’t compete with that. It couldn’t be any further away from action. It’s the least bad ass thing one could do for their health.

Au contraire…

Getting adequate sleep is the single most important thing one can do for bad ass weight loss results and to optimize health.  It’s potentially more important than both diet and exercise put together.

Sleep plays a major role on our endocrine system, and a poorly functioning endocrine system is detrimental to fat metabolism and weight loss. Don’t throw in the gym towel just yet, and absolutely keep to the healthy diet rolling – but if not complimented with quality sleep, the action put in during the day is likely done in vain.

We have to understand that sleep is still putting in the work. There’s so much that goes on while we’re asleep that cannot be achieved while we’re awake. These are fundamental processes that our bodies evolved to do every night.

During sleep, and only during sleep, the glymphatic system washes the brain, clearing amyloid plaque and toxins (1). Memories are consolidated from short to long term. Part of our immune system repairs after a day on the battlefield, while another part sets out to hunt down cancer cells (2).

If sleep was really a waste of time, like Thomas Edison once said, then why is it so heavily embedded in our DNA?

The connection between sleep and weight loss. 

If we don’t get enough sleep and/or quality sleep, the important processes our bodies need to perform simply don’t occur.  Through direct and indirect ways, this leads to weight gain or struggle in losing weight.

There are 2 types of fat. Visceral (deep) fat and subcutaneous (under the skin) fat. It’s the former that is largely influenced by inadequate sleep. A study published in the Journal of Sleep found that, over a 5 year follow up period, those that slept less than 5 hours had significantly higher BMI and body fat deposit than those that got 6-7hours. Using CT scans to measure fat deposition, they discovered visceral fat was the most predominant (3).

This could have been due to shifts in metabolism or increased total calorie intake due to sleep deprivation. It’s also commonly known that those who sleep fewer hours have a tendency to reach for high sugar and highly processed foods (4).

Sleep also affects how the body burns calories. Let’s say we take a group of people and put them on a calorie restricted diet, and force them to sleep 5.5 hours per night.  They’ll lose 55% less body fat than a group of people with the same calorie intake, but getting 8.5hours of sleep. This is exactly what researchers at the University of Chicago found (5). Moreover, it’s not just weight loss we’re talking about here. The sleep deprived group still lost weight, but they lost 60% more muscle mass, compared to the well slept group. We know that muscle is the fat burning machinery, so we want to sleep well to conserve it for long term fat loss.

We also know that lower muscle mass, particularly associated with overweight, is strongly linked to increased risk of Type II Diabetes (6)  The large Nurses health study, over a period of 16 years, discovered that Women who reported to sleep 5hrs or less were 15% more likely to be obese than those reporting 7 or more (7).

So what’s going on under the hood that causes such a dramatic effect on weight management?

As mentioned before, sleep quality is a major determinant for endocrine (hormonal) regulation. Let’s now talk about which hormones are influenced and how this plays out either physiologically and behaviourally. 


Most of us know it as the sleep hormone. Melatonin modulates and regulates our bodies whole circadian rhythm.  It requires the setting of the sun (darkness) to be triggered in the brain, as well as a distinct cyclical pattern to influence optimal sleep patterns.

Melatonin, not only regulates sleep, but also plays a role in metabolism through its influence on brown fat. Brown fat is stored in pockets throughout the body, specializing in energy expenditure and thermogenesis (8). It’s dense concentration of mitochondria (energy factories of the cell) can increase overall metabolism, increase fat store usage (9) and may have other health benefits too.

We want to encourage the maintenance and development of brown fat as much as possible. If we don’t allow our body to produce melatonin with a healthy cyclical sleep pattern, we could suffer from lower resting energy expenditure, low energy levels, and difficulty managing body weight.

Human Growth Hormone (HGH)

HGH is known as the “youth hormone” because it influences restoration and repair of the body. It keeps the skin young, maintains bone density and stimulates energy production. It’s also a key player in fat metabolism and muscle growth and repair (10).  After making it count in the gym, a quality nights sleep ensures the hard work is paid off. Muscles are given the best chance to recover and build, so they’ll best serve you in burning fat, long term.

The majority of HGH is produced during sleep, especially slow wave sleep.  We get the biggest peak of GHG about 1 hour after falling asleep, then roughly every 90 minutes with each sleep cycle. Pushing bed time later reduces the initial spike of HGH and shorter sleep duration simply means less sleep cycles, hence sub-optimal HGH levels (9).


One of the most consistent things that sleep scientist see in people that are sleep deprived, is elevated cortisol levels. Cortisol is the main stress hormone.  It’s often scorned as the evil hormone, but in fact, it’s important for human function and performance. It starts to become a problem, however, when it’s secreted too often, at the wrong time, and for too long. 

Cortisol levels are normally at its lowest just after sleep, and at their highest just after waking (11).  It plays an inverse role to melatonin. While cortisol drops, as we wind down for the night, melatonin is able to set in to induce sleep. After a restful nights sleep, inline with the rising of the sun, melatonin is turned down and cortisol levels rise to power us up for the day (12).

If we don’t sleep, this rhythm is disturbed and cortisol levels stay elevated. Even while relaxing on the couch, scrolling the phone or watching NetFlix, the brain misinterprets this as a stress. This, in combination with the commonly stressful modern lifestyle, causes dramatic shifts in our fat and muscle tissue. Chronically elevated cortisol levels are capable of breaking down muscle tissue, and ramping up fat storage.

Here’s how it works. High cortisol, to the primitive brain, means “danger”. Danger means – 1) increase blood sugar to prepare for fight or flight. 2) Conserve energy for the potential risk of starvation.  It’s thought that muscle is spared to make glucose available, as well as to reduce overall energy expenditure. Muscle tissue is very metabolically  active – metabolically “expensive” one could say.  The unused glucose in the blood is then stored as fat (we didn’t fight or fly away), stashed away incase the “danger” leads to a period of starvation.

Sleep deprivation is quite literally sabotaging the “action” we take to achieve our weight loss goals.


Insulin in relation to sleep is intertwined with the physiological effects of previously discussed Cortisol. When we get deep restorative sleep, the brain uses a large amount of glucose. The interruption of sleep leaves unused glucose circulating the system.  This, along with cortisol’s influence on blood glucose, increases the demand for insulin. Our system keeps pretty tight control on glucose levels in the blood, and hence ramps up insulin to shift it into either muscle or, more likely, fat cells. Insulin isn’t called the fat storage hormone for nothing.  The long term impact of this hormonal dance is insulin resistance and potentially Type II diabetes (12).


This one affects the guys more than the gals, but testosterone still plays a role in women. Testosterone is another hormone that drives metabolism, especially fat burning. It’s also, as you guessed it, very dependant on sleep.  Throughout the day, as we go about our business,  testosterone levels are gradually declining.  When we go to sleep at night, it’s our body’s opportunity to stock pile more testosterone for the following day. We just have to do the math to figure out that less sleep time equals less testosterone.  Over time, accumulating more and more sleep debt, can lead to testosterone becoming hazardously low.

In a study found in the Journal of American Medical Association,  just one week of sleep deprivation (5hrs per night) caused a 15% drop in testosterone levels in young males.  This may not sound like much, but it equates to the testosterone level of someone 15 years older (13).  Sleep deprivation is now making us fat AND old. 

Low testosterone levels have also been linked to low mood & vigour, lack of libido, chronic fatigue and poor concentration (14). With these symptoms, it’s no wonder that willpower wears thin pretty quick when working towards health and weight loss goals.

Leptin & Ghrelin

Last but not least, the appetite hormones. Leptin is the hormone that tells our brain we’re satiated after a meal. Ghrelin tells it that it’s time for a meal. When the eb and flow of these hormones is stable, we’re full when we’re full, and hungry when we’re truly hungry. We’re also much less likely to over eat or crave calorie dense foods. 

In true fashion, sleep is a major regulator of leptin and ghrelin hormones. Under analysis, the 2 hormones move in completely opposite directions.  One Sleep study showed that sleep deprivation can increase ghrelin levels by as much as 15%, and lower leptin levels by the same amount (15). Could we then presume, that when chronically sleep deprived, we’re 15% hungrier, 15% less satiated, and possibly 15% more frustrated along our journey to good health? 15% less likely to achieve our goals?

In a captivating podcast discussion between Joe Rogan and Sleep neuroscientist, Matthew Walker, Joe asks: “don’t people that sleep less…eat more…or eat more sh***y food?” 

Dr Walker explains just how true this is. If you put healthy people on 4 or five hours of sleep for just a short period of time, they will on average, eat between 200-300 more calories per day.  Over a year, this adds up to over 100,000 unnecessary calories. Contributing to roughly 30lb of excess body fat.  He confirms that these folks are more inclined to reach for highly processed, carbohydrate rich foods and lean away from healthier foods like greens, nuts and seeds, healthy fats and protein.

What about sleep and performance?

Every one of us want’s to perform at our peak.  We want to show up and deliver. We want to learn, we want to master, we want to grow.  Afore mentioned Dr Walker believes that sleep is the best performance enhancer we have available to us.

During sleep the brain goes through processes of consolidating learned information. An athlete practicing a skill, a student consuming an abundance of information, or a professional honing their craft – can experience a 20-30% improved performance after a quality nights sleep, compared to those that don’t. Sleep allows us to sculpt and refine the things that we work so hard to develop in our waking hours.

This is a big one for those of you working out to lose weight & get fit. When under slept, we’re just not able to give it everything we’ve got – even when we think we might be. For example, the average gym goer, may walk out of the gym feeling spent. Pleased after a hard session put in.  While this definitely should be celebrated, it’s possible that said gym goer had burned far less calories, relative to their perceived exertion.  When poorly rested, blood flow and lung capacity are reduced, lactic acid accumulates faster and the time to achieve physical exertion drops dramatically. Basically they didn’t work out as hard as they thought they did. 

The implications of this on exercise consistency is significant too. Even when we start to enjoy the challenge of it, this performance limiting factor can be a source of discouragement.  We all want to see progress in our performance. We’re more likely to adhere to our sport or exercise of choice when we see improvements in performance, regardless of aesthetic change.

Wrapping up

So often in weight loss, people get frustrated and disheartened. People think that its them that are the problem. Maybe you know what i’m talking about?  Before losing hope, understand that it’s not you. If you’re doing all the right things during your waking hours, but still not getting the results – YOU are not the problem. 

Take a look at your sleep habits and get to work on putting them on track. We now understand some of what goes on when we sleep, and what can go awry when we don’t.  Once we get below 7 hours of sleep, impairments in the brain and body can be objectively measured.  Even when we subjectively believe to be operating well on a smaller amount of sleep, physiologically, there’s a whole lot going on that is detrimental to performance, health and of course ability to lose weight.

It’s time that sleep stopped being an after though and was put right up there as top priority.

Keep taking ACTION toward your weight loss and health goals. Continue to optimise the diet and fitness regime thats best for you. Keep learning, keep prepping, keep challenging. By all means, work hard to achieve the health you deserve. Just keep in mind that Sleep is the main piece of the puzzle here. It weaves all the other heathy habits together. Take pride in emphasizing high quality sleep habits, rather than guilty or ashamed for being what cultural norms might call “lazy”.


  1. Brain may flush out toxins during sleep
  2. Sleep and immune function
  3. Sleep Duration and Five-Year Abdominal Fat Accumulation in a Minority Cohort:The IRAS Family Study
  4. Sleep and obesity
  5. Lack Of Sleep Can Make Dieters Lose Muscle Instead Of Fat
  6. Skeletal Muscle Insulin Resistance: Roles of Fatty Acid Metabolism and Exercise
  7. Association between Reduced Sleep and Weight Gain in Women
  8. Brown adipose tissueRecent insights into development, metabolic function and therapeutic potential
  9. Melatonin helps control weight gain as it stimulates the appearance of ‘beige fat’ that can burn calories instead of storing them, study suggests
  10. Growth Hormone Secretion during Sleep
  11. The Intricate Role of Growth Hormone in Metabolism
  12. Interactions between sleep, stress, and metabolism: From physiological to pathological conditions
  13. Effect of 1 Week of Sleep Restriction on Testosterone Levels in Young Healthy MenFREE
  14. Sleep loss dramatically lowers testosterone in healthy young men
  15. Sleep deprivation and obesity in adults: a brief narrative review

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