How Sleep Impacts Fitness Weight Loss & Diet

For the 20 years I've been home personal training clients across Liverpool and Wirral, I've been a strong advocate of sleep, knowing the basics of how sleep can have an impact on our ability to lose weight and gain lean muscle tissue, I always made a point for my clients to get good sleep. Although my knowledge of sleep and its impacts was limited to the occasional chapter in health & wellbeing books that I'd read over the years, a couple of years ago, I was greatly inspired by Professor Matthew Walkers book 'Why we sleep'. I say greatly inspired but, I'd also add the word shocked!

Although I knew some of the basics, I was surprised how much sleep and poor sleep significantly impact us. So, when searching the trail of scientific literature, I realised my effort supporting clients with sleep patterns was below the bar. It was clearly evident that sleep significantly impacts every central physiological system of the body and every operation of the mind.


In this blog, I will share with you the critical findings of my research in two parts. In the first part, I will discuss how sleep directly impacts our body transformation efforts. In the second part, I will share the indirect impacts on our habits and behaviours, which affects fat loss, feeling good, gaining lean tissue, and maintaining good levels of mental clarity.

Side note, to learn how to make incredible changes to your body without endless hours in the gym, try my recent blog, Fitness Goals, Mindset, and Lifestyle 

Before we move into the good or bad news, depending on how well you sleep, I will quickly explain the different phases of sleep and what they're generally known to do:

NREM – Non-Rapid Eye Movement Sleep (Stages 1, 2 & 3)

Stage 1 – This can last for 1-5 minutes. It's that pleasant feeling of slowly drifting away from where you're still aware of the external world, but you can feel yourself moving into that beautiful zone of unconsciousness

Stage 2 – Following stage 1, you enter the unconscious zone where many changes happen throughout the brain and body and a deeper state of relaxation. Your body temperature drops, muscles loosen, and both your heart and breathing rate slows down.

Stage 3 - Known as Slow Wave Sleep or Deep sleep, this is where the rubber meets the road, and a great deal of positive, beneficial changes take place in the body. Although cognitive and physiological benefits are in this stage, the latter has a higher ratio of positive changes around the body. Cells, muscles, immune function, and hormonal changes are happening nicely here. Deep sleep typically occurs in the first half of our night's sleep and provides a higher degree of physiological recovery. Slow-wave sleep is a critical state of sleep for everyone, especially if you're exercising and want your body to heal well from the stimulus.

REM – Rapid Eye Movement Sleep

REM sleep is the dream zone where positive physiological changes happen, but a higher degree of cognitive benefit will occur here. During REM, we will be in the dream state, and this area of sleep is where our mental process is enhanced. Memory, learning and many more cognitive systems greatly benefit from this area. If you want a clear mind and the enhanced ability to focus, concentrate and recall, this is the big zone where this takes place and will typically happen in the second phase of our sleep cycle.


Direct effects of sleep on fat loss and lean muscle gain


Testosterone Production – Just 4 nights of insufficient sleep has been shown to decrease testosterone levels to the same point as a person 10 years older than you. If this doesn't shock you, then I don't know what will! You only need 4 nights of inadequate sleep to drop testosterone levels by 10 years, which is quickly done. I can undoubtedly confirm I've had my fair share of consistent sleepless nights over the years. If you didn't know, testosterone is a critical hormone to us all (not just men). We need this primarily for lean tissue growth and maintenance of our bones and connective tissue. Along with the apparent benefits of having a more robust musculoskeletal system for longevity, we need lean tissue to help reduce body fat by increasing the metabolic engine.

Online Personal Training

One of the challenges I find with the majority of my online personal training clients is their busy lives do not aid in their sleep routines so showing them this information (facts) normally does the trick so, I hope you are paying attention?

Blood Sugar Regulation – Poor sleep quality directly impacts insulin sensitivity and blood sugar regulation. According to an article in Nature Metabolism (Hyperglycemia is associated with impaired muscle signalling and aerobic adaptation to exercise) the authors reported impaired muscle signalling and aerobic adaptations in animals and humans with poor blood sugar regulation. So basically, the worse your sleep, the worse your performance and the lower your returns from Exercise.


Metabolism – Poor sleep harms almost all our metabolic processes. Regardless of our health & fitness goals, impaired metabolic function is simply deleterious to lean muscle gains and fat loss. In this study (sleep & metabolism), the authors show the cascade of adverse metabolic outcomes from poor sleep patterns.


Indirect effects on body transformation via our behaviours


The nervous system – The sympathetic branch of the autonomic nervous system, the area responsible for our fight or flight stress response, is ramped up when your sleep is reduced. Chronic stress is a bad place to be. Mentally and physically, you will decline rapidly! In addition, you will fatigue very quickly; use stimulants to keep you going and sedatives to slow you down. This is a lose/lose scenario as the use of both sedatives and stimulants, most popular being caffeine & alcohol, place more stress on the system and don't allow for recovery required when you sleep. Using sedatives such as alcohol may help some people sleep; however, being sedated impairs your ability to move through the sleep phases resulting in the loss of critical physiological and cognitive recovery.


Hunger – The onset of poor blood sugar regulation comes to the inevitable poor control of your appetite. Erratic swings of your blood sugars will result in powerful cravings, often sugary based foods and far less wholesome foods. You don't need me to tell you the negative impact of high sugary food consumption on your body transformation efforts!


Energy – The apparent lack of mental and physical energy will significantly reduce your willingness to eat healthily and exercise. The battle you now face will be to simply get through your day. Hardly and optimal state when you want to look good, feel great and perform at your best in Life!


Mental Health – According to sleep expert Professor Matthew Walker, there are no Psychiatric disorders where sleep patterns are normal. When trying to improve your body shape and living at your best, your mental health is obviously a top priority. Without this, the essential pillars of Life start tumbling down, and you're left in survival mode trying to make it through each day. This is clearly not the place to be if you're trying to achieve any goals in Life.


As you can see, the deleterious effects of inadequate sleep are significant and in order for you to make changes within your lifestyle to improve your sleep will take a little discipline. If you struggle with self-discipline, visit my page which discusses how you can improve discipline with eh right mindset. Weight loss takes discipline and discipline takes courage  

As a Personal Trainer and Coach for most of my adult life, I've primarily focused on Exercising closely, followed by nutrition and sleep only being a consideration. Today this is certainly not the case. As you can see, the impacts poor sleep has in such a short space of time is staggering. I've had to concede that sleep is the foundation of good health and body transformation as this will provide a stable platform on which Exercise and nutrition can be effective.

Due to the complexities and difficulty of implementing effective Exercise, I will always lead with this when helping my Home & Online personal training clients, but sleep will certainly sit next to exercise in order of priority, both for my clients and me. So bottom line, if you want to be Fit, Lean, Healthy, Strong, and Performing at your best in Life then, get some good sleep, my friend!


Keep healthy





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