We spend a third of our lives sleeping, and although to some people it may seem a waste of time because literally while we sleep we are not ‘producing’, the reality is quite different. And it’s not just about resting, but our brain hides a real neural “switch” that, during sleep, dictates whether our body will build muscle, burn fat or, on the contrary, enter a state of metabolic emergency.
What was seen. Joint research from the University of California and Stanford University, published in September 2025 in the prestigious magazine cell, managed to map this mechanism. The researchers identified a specific neuronal circuit in the hypothalamus composed of two fundamental players: the GHRH neuron, which acts as the “accelerator” of growth hormone, and somatostatin, which functions as the “brake.”
Its balance is essential to regulate how much growth hormone is released during sleep. And it is not something that should be left in the background or only for children who are growing, but this hormone is essential to be able to build muscle, break down fat or even regulate glucose.
In the first half of the night. Not all moments of the night are worth the same, since approximately 70% of daily growth hormone secretion occurs during the first cycle of deep sleep, also known as the N3 phase.
In this way, if we shorten our hours in bed and miss that key rest, deep quality sleep is not achieved and the desired peak of growth hormone does not occur. What this directly leads to is accumulating fat and losing muscle tissue.
The hunger. The muscle is not the only one affected, but our diet also suffers chemical sabotage. Here research has shown that little sleep drastically alters our appetite-regulating hormones.
A large meta-analysis published in the journal Obesity Reviewsthat analyzed 21 studies with 2,250 participants, pointed out that short sleep causes leptin, which is the hormone that sends the signal of satiety, to decrease by 18%, while ghrelin, the hormone that triggers hunger, increases by 28%. This makes us have a greater appetite and prefer to consume more calories if we do not sleep enough hours.
The metabolic risk. The impact of not sleeping goes far beyond hunger and the scale, since at a metabolic level, sleep restriction reduces insulin sensitivitywhich directly increases the risk of developing type 2 diabetes.
More and more data. If you still had doubts about the benefits of sleeping correctly, we already know that having a good sleep allows us to be more productive and better integrate the different knowledge that we learn in our brain. But to this is now also added the ability to ‘create’ new muscle, making the smartest decision to be sleeping, although for some it is not very productive.
Images | Slaapwijsheid.nl Anastase Maragos
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