The less you sleep, the more you are likely to eat.

Sleep is more than just a period of rest; it plays a crucial role in various physiological and metabolic processes, including weight management. Dr. Matt Walker, an esteemed neuroscience and psychology professor at UC Berkeley, asserts that insufficient sleep, six hours or less for consecutive nights, is linked to increased eating tendencies.

This article explains five scientific (and surprising) facts that reveal the intricate relationship between sleep loss and weight gain. The secret to losing weight might be hidden in your sleep, not your diet!

Increased appetite.

Two hormones are mainly responsible for your appetite and hunger. Let us focus on the first one: Ghrelin (yes, please, call it Gremlin, it’s OK). Ghrelin is responsible for triggering hunger. After several hours without eating, it is only natural that the levels of this hormone increase in your blood flow, and consequently, your desire to eat.

However, science has proven that lack of sleep perturbs the balance of this hormone, making it behave oppositely, overproducing even when it should quell hunger. In other words, excess of Ghrelin circulates in your blood signalling to your brain that you are hungry, always.

But this does not occur after years of poor sleep; it happens as soon as two continuous nights of sleeping six hours or less. Ghrelin goes out of balance and cannot control its signal, making you feel … like a Gremlin.

Reduced satiety.

The second hormone of this duo is Leptin. The main function of Leptin is to send a signal to your brain letting it know you are full, also called the satiety-signalling hormone. When leptin is naturally released assuming good sleep hygiene, levels in your blood are high, and your appetite is tamed. But what happens when you have cut down on sleep? Insufficient sleep triggers a reduction in Leptin production, resulting in a continuous and insatiable appetite.

So, it is not only one, but these two hormones (Ghrelin and Leptin) acting together that will challenge your appetite and satiety, and without knowing, you will start eating more. In criminal terms, this is called double jeopardy, or being punished twice for the same offence!

Dr. Eve Van Cauter’s extensive research at the University of Chicago underscores this detrimental metabolic effect, revealing that sleep-deprived adults may consume an extra 300 calories daily. If we scale this number to a year, and calculate it based on effective working days, it adds up to 70,000 extra calories or 15 to 20 pounds of gain weight every year.

Burn More Calories Myth.

Some would argue that by putting in more waking hours, individuals who sleep less move more, hence produce more energy and may burn more calories per day. Dr. Matt Walker has proven this statement wrong. After studies with healthy individuals in his lab, an adult who is awake for four more hours only burns 147 additional calories per day which, on the one hand, does not compensate for the additional calories gained via food, and on the other hand, are fewer calories than what the body uses while at sleep. “Sleep, it turns out, is an intensively metabolically active state for brain and body alike”. 

Ravenous cravings.

Sleep loss not only amplifies hunger but also skews food preferences. Studies reveal a 30 to 40% surge in cravings for sugary treats, carb-loaded delights such as bread, pastry, doughnuts and pasta, and salty snacks following inadequate sleep.

There is a reason why this happens across the board, and I am no exception: I go for the bread when tired. After several nights of shorter sleep, a region in the brain in charge of thoughtful judgement and controlled decisions called the prefrontal cortex gets silenced. In contrast, a more primitive deep-brain structure that drives desire gets amplified. The result: is a heightened tendency to reach for unhealthy options, based on poor judgement, less self-control, and an increased desire for immediate satisfaction.

Hold on to fat.

But what if we go on a strict diet during this time of shorter nights and we are disciplined in controlling our food choices? We would think a hard-core, low-calorie, keto, fasting, or low-carb diet would do the magic to shed those extra pounds. The answer is yes. Regardless of sleep loss, you will lose some weight. The quid here is, where is this weight loss coming from?

While sleep-deprived, the body becomes concerned about giving up fat, instead, the primal survival instinct is to drop lean mass (muscle) and keep the fat for future energy needs (muscle is not a source of energy for the brain or body). From an evolutionary perspective, the brain reads sleep deprivation as danger and survival, therefore the body hoards energy-rich fat reserves during times of perceived threat (sleep loss).

As a result, attempting to shed weight during periods of shortened sleep might lead to muscle loss rather than fat reduction. So, when going on a diet, try to put sleep into the menu to guarantee effective results.

In the relentless pursuit of modern life, professional growth, and never-ending TV shows, sleep often takes a back seat. However, we believe that by understanding the “why”, humans are better equipped to make smarter choices. Understanding the intricate connection between sleep loss and weight gain may underscore for some the urgency of prioritizing quality sleep.

Stay active and sleep well,

Rosana