A new study published in Science Advances has found how a single night of poor sleep can switch on genes in fatty tissue, increasing the body's ability to store fat. Meanwhile the opposite happens in muscle tissue: complex proteins break down causing muscle atrophy.
The report, conducted by Swedish scientists, is the first of it's kind that suggests interrupting the body's sleep cycle can affect the body's metabolism.
“Shift working and sleep loss are very common these days, that’s why it’s important to investigate this,” said lead author Dr Jonathan Cedernaes from Uppsala University in Sweden.
“We believe our new study findings provide evidence for how chronic sleep loss and shift work may increase risk of obesity and type 2 diabetes, while at the same time decreasing your muscle mass.”
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“We also found evidence this could be linked to changes in the circadian clock, which is known to regulate [the] 24 hour rhythms of how these key tissues utilise metabolic fuel and respond to stimuli.”
Scientists took the blood, muscle and adipose tissue ( fatty tissue) samples of 15 healthy participants both after a night of normal sleep and following a night where they stayed awake, similar to a night shift. Eating and exercise were kept constant to limit other factors that could affect metabolism.
Another test they used look at DNA Methylation in tissues - switching on sections of the genetic code which programme specific cellular tasks.
Results showed that methylation both increased and decreased in the fatty tissue cells DNA - which could be responsible for fat storage.
Meanwhile, muscle tissue saw a decreased activity in the genes responsible for maintenance of muscle.
Dr. Cedernaes tells Men's Health this could be "due to disrupted hormonal levels, including the altered (increased) cortisol levels we observed, but it's possible that other hormones contribute (such as anabolic growth hormone, or testosterone).
"Furthermore, these hormones can be shifted or blunted through disruption of circadian rhythms, which we also found evidence of. (For example), cortisol can regulate circadian rhythms in peripheral tissues, so together with rhythms such as core body temperature this regulates how peripheral tissue rhythms are in sync with the brain's pacemaker, which in turn is regulated (and reset on a daily basis) primarily by the light-dark cycle.
"Cortisol levels can thus be impacted both by increased stress activity due to continued wakefulness, and interlinked with this, due to a disrupted circadian rhythm of its release/levels."
“These observations are thus the first to offer an explanation at the tissue level for two seemingly contrasting clinical phenotypes seen following experimental sleep loss in humans: gain of fat mass, occurring concomitantly with loss of lean mass,” the study authors wrote.
Further research will be needed to confirm the findings but next time your boss asks you why you're late, ask them if they want you to look husky.