Neuro Athletes,

If you’re an early bird like me, living in New York City, then you know you’re living in the city that never sleeps. What does that mean? That means that you’re up at 6AM to Citbike to the gym, crushing your workout, getting your post-workout coffee, frantically running to catch the subway to get to your desk for your 10AM meeting and repeat. It’s definitely a struggle to maintain a work-life balance and most of the time we end up sacrificing our sleep in order to keep it up. 

This theme of insufficient sleep ties into weight gain. When we think of the key factors controlling our weight, most of us probably think of diet and exercise. We all know that we have to try to eat healthily and that it’s important to take regular exercise if we want to keep our weight in check. But it might be interesting to learn that there’s a third factor which is just as important and often overlooked: sleep.

To get a sneak peak into this topic, check out the Instagram reel I did on this topic we get into the newsletter!

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Primer 

Your total body weight is equal to fat plus muscle mass. So, if you do experience weight loss while simultaneously maintaining or growing muscle mass your muscle mass then, the source of your weight loss is achieved from losing fat. In order to actually lose fat, you’ll need to follow a calorie deficit diet and maintain muscle via resistance training. A case control study by Chaput and Tremblay (2012) determined whether sleep quantity and quality can predict the magnitude of fat loss in 123 men and women who were subjected to a caloric restricted diet of 700 kcal/day. The study recorded body fat mass, sleep quality, sleep duration at baseline and at the end of the program. After 24 weeks, they observed 4.5 kg mean weight loss of all participants, 76% of which came from fat storage. The positive correlation between sleep duration and fat loss, suggests that sleeping habits can influence the success of weight loss intervention and should be taken into consideration when starting a diet.

Interestingly, Verhoeft et al. (2013) found that a longer average sleep duration maintains weight loss and perpetuates further weight loss and conversely, those who sleep shorter duration gain weight. They followed 98 healthy subjects (ages 28-35) over a two month intervention with 3 month and 10 month follow-ups. They found that the average weight loss was 10 % after two months of dieting and 9% and 6% after 3- and 10- month follow-ups, respectively.

Sleep and Insulin Resistance

A single night of partial sleep restriction on parameters such as insulin sensitivity have also been tested. In 2010, Donja et al. designed a case controlled study, following 9 subjects (5 men, 4 women) after a night of normal sleep (2300 - 0730h) and after a night of 4 hours sleep (0100 - 0500h). They noted that sleep restriction resulted in increased endogenous glucose production compared to the night of unrestricted sleep, increasing glucose availability in blood plasma. More importantly, they noted a decrease in insulin sensitivity, suggesting poor cellular response to insulin.

What does it mean to develop insulin resistance? Insulin is a hormone produced by the pancreas to help transport glucose from the blood into the cell. When you develop insulin resistance then, the cell fails to import glucose into the cell. This non-functional insulin results in the production of more insulin (hyperinsulinemia) so that your body can attempt to maintain healthy blood sugar levels. Elevated levels of insulin can result in weight gain, which, in turn, makes insulin resistance worse.

Hyperinsulinemia is also associated with the following conditions:

• Elevated triglyceride levels

• Atherosclerosis (hardening of the arteries)

• Hypertension (high blood pressure)

More importantly, insulin resistance is also the main feature of metabolic syndrome - a set of identifiable features that link excess fat around the waist and insulin resistance to increased risk of cardiovascular disease, stroke and Type 2 diabetes.

Noted signs of metabolic syndrome include:

• Elevated blood glucose levels

• An elevated triglyceride level

• Low levels of high-density lipoprotein (HDL) cholesterol

• High blood pressure

If these findings haven't shaken you up then, you might feel differently knowing that the impacts of short-term sleep restriction also activate the sympathetic nervous system (our flight or fight response). Experimental studies have shown that limited sleep increases the concentration of circulating cortisol. Cortisol, a stress hormone, upregulates hormones such as adrenaline, which increase your alertness in order to help you navigate a moment of distress.

Cortisol also serves to increase the amount of glucose available to provide the brain and other organs energy to function at maximum capacity. So, when cortisol levels are high, gluconeogenesis (glucose production in the liver) occurs to increase glucose while simultaneously inhibiting insulin secretion, resulting in greater glucose availability. This mechanism tips the scale towards diabetic symptoms and cardiovascular disease.  

Sleep, Hunger and Satiety Hormones

The battle between hunger and the feeling of satiety is a tug of war between two hormones. Leptin is a hormone that suppresses hunger; ghrelin is a hormone that stimulates hunger. Spiegel et al., followed 12 healthy men to determine whether partial sleep alters appetite regulation. Two days of sleep restriction, resulted in an 18% decrease in leptin and 28% increase in ghrelin, resulting in increased hunger and appetite.

Therefore, poor sleep disrupts hunger and satiety signals, increasing likelihood of overeating, making it difficult to adhere to a calorie deficit diet. A simpler and secondary explanation is that the more time you spend awake, the greater the number of snacks you have per day, increasing your caloric consumption. 

Sleep and Motivation

Studies have also shown the impact of sleep on mood and motivation. The lack of sleep increases fatigue, anxiety, and mood disturbances all of which compromise our motivation to maintain a strict diet. Motivation is also needed for resistance training and muscle preservation. Therefore, poor sleep decreases training motivation, resulting in inferior hypertrophic stimulus and less muscle retention.

Resources on How to Get more Quality Sleep

1. The myths and truths of sleep optimisation

2. Using glycine for better quality sleep

3. Sleep quality for athletic performance

4. Vitamin D and sleep performance

Until next time,

Louisa x