A 2025 study found that when you shortchange your sleep, your cells don’t merely get tired—they go into crisis mode, burning fuel inefficiently, scaling back repairs, and choosing survival over function. The effects start after a single bad night.
The findings reframe sleep not as a lifestyle habit, but as a biological maintenance system, one the body cannot afford to skip.
“Sleep deprivation hurts,” Jennifer Tudor, an associate professor of biology at Saint Joseph’s University in Philadelphia and coauthor of the study, told The Epoch Times. “The data [show] that regular, consistent sleep deprivation is harmful for long-term health.”
The Body Doesn’t Shut Down During Sleep
The body runs on fuel, and metabolism is the process by which cells produce and use that fuel. Metabolism has two sides: catabolism, during which the body breaks down nutrients to release energy, and anabolism, during which the body uses energy to build and repair tissues, proteins, and brain connections.
Sleep plays a critical role in the balance between this breakdown and repair.
“Many people used to think that sleep is when the body ‘shuts down,’” Tudor said. “In reality, sleep is a robust process with the cells of the body highly active and working.”
During wakefulness, the body is mostly in a catabolic state, breaking down fuel to power activity. During sleep, it shifts toward an anabolic state, repairing tissue, restoring energy, and improving communication between brain cells.
The energy hypothesis of sleep proposes that sleep pressure builds because cells gradually run low on energy during wakefulness. As cells use adenosine triphosphate (ATP), the body’s main energy molecule, it is broken down into smaller molecules, including adenosine. As adenosine builds up in the brain during waking hours, as cells are continuously using energy, it creates the feeling of sleep pressure and signals that it is time to rest and replenish energy stores.
What Happens Inside Your Cells
When sleep is cut short, the body enters a stressed, inefficient state.
At the cellular level, mitochondria begin burning fuel less efficiently, producing more heat and less ATP. As a result, the body has to burn more fuel just to maintain basic functions, creating an energy deficit at the cellular level. The resulting inefficiency generates more reactive oxygen species, which cause oxidative stress and damage cell structures.
With energy in short supply, cells begin to prioritize survival over higher-level functions. Neurons are especially affected because they require a constant, high supply of energy.
“In an attempt to generate more energy and get back to energetic homeostasis, sleep-deprived cells are also driven into a profoundly catabolic state in response to the negative energy balance induced by periods of sleep loss,” Sierra Feeney, a neuroscience doctoral student at the University of Iowa and coauthor of the study, told The Epoch Times.
As a result, energy-intensive processes such as forming new connections between brain cells, building proteins, and repairing damage are scaled back so basic survival can continue.
“To avoid cell death—and eventual death in extreme cases—due to energetic failure, sleep-deprived cells shunt energy away from not acutely essential functions to ensure that there are sufficient resources available for essential functions,” Feeney said.
She said that this trade-off is critical for long-term cellular and overall survival, even if it comes at the cost of some functional deficits.
The trade-off reflects a basic biological reality, Tudor said: Survival comes first, even at the expense of thinking and memory.
Metabolic Toll: Weight Gain, Cravings, and Disease Risk
Over time, prioritizing survival over repair begins to take a toll on the body.
Because sleep is crucial for the body’s repair and maintenance work, inflammatory signals increase, and tissue repair slows. Muscle tissue repair and protein production decrease, which can lead to loss of lean muscle mass. Because muscle is one of the body’s most metabolically active tissues, losing muscle makes metabolism less efficient and reduces the number of calories the body burns at rest.
Sleep loss can also affect behavior in ways that compound the damage. Lack of sleep causes the reward centers in the brain to become more reactive while the frontal cortex—responsible for decision-making and impulse control—becomes less active. This makes high-calorie foods more appealing and harder to resist, which helps explain why sleep deprivation is linked to increased cravings and higher calorie intake.
Hormonally, the picture is equally disruptive. Losing sleep raises the stress hormone cortisol, pushing the body toward energy storage. At the same time, sleep loss reduces insulin sensitivity, meaning that cells do not respond to insulin as well, leading to higher blood sugar and metabolic dysfunction.
“You might notice stronger cravings for high-calorie foods, difficulty focusing, low energy, and a greater reliance on caffeine to stay alert,” Dr. Alberto Ramos, a professor of clinical neurology and research director of the sleep disorders program at the University of Miami Miller School of Medicine, told The Epoch Times. “These are all signals that your body is struggling to keep its energy balance intact.”
The combination of greater cravings, insulin resistance, inflammation, and reduced muscle mass creates conditions that favor fat storage. Chronic sleep loss—regularly falling short of the recommended amount of sleep over weeks, months, or longer—is associated with obesity, cardiovascular disease, and Type 2 diabetes.
The Brain Pays a Separate Price
Sleep loss affects not only the body but also the brain’s ability to function and adapt.
The buildup of adenosine does more than make you feel sleepy. It activates kinase, a cellular energy sensor that shifts cells into conservation mode, reducing energy-intensive processes.
At the same time, astrocytes—support cells that help brain cells function properly—release ATP into the space around neurons, where it is quickly converted into adenosine, further amplifying the signal to slow down and conserve energy.
As adenosine levels rise, neural activity and synaptic plasticity—the processes involved in learning and memory—begin to slow. The result is the foggy thinking and poor memory that most people associate with a bad night’s sleep.
When this happens repeatedly, the effects may not be as temporary as many people assume.
“Chronic sleep loss forces the brain into an energy deficit, prompting it to cut back on memory and repair processes just to get by,” Ramos said.
What Protects Your Sleep
Protecting sleep is more than avoiding fatigue—it is about protecting the body’s energy balance, metabolism, and brain function over the long term.
General recommendations suggest that adults get at least seven hours of sleep each night, although individual needs vary. Even a single night of insufficient sleep can lead to functional impairments.
In humans, this is “roughly equivalent to staying up until 3 a.m. and still waking up at 6 a.m. for one night,” Feeney said.
Many people try to cope with sleep loss using caffeine, naps, or weekend catch-up sleep, but these strategies provide only temporary relief.
“They don’t resolve the underlying energy deficit in the brain and body,” Ramos said. “Relying on these strategies over time can disrupt your natural rhythm and make the problem worse.”
The single most protective habit is consistency, he said.
“Maintaining regular sleep and wake times helps protect your body’s energy balance and gives your brain the opportunity to restore the essential fuel it needs to function at its best,” Ramos said.
Healthy sleep is defined not just by duration but also by quality and timing, he said.
“Healthy sleep means getting seven to eight hours each night, sticking to regular sleep timing, and waking up feeling refreshed and energized,” Ramos said. “This kind of sleep allows the brain to replenish its energy reserves while supporting memory, metabolism, and general well-being.”
Because people often feel better after catching up on sleep, it is easy to assume that the body has fully recovered. But some evidence suggests that metabolic changes may accumulate over time—which is why researchers increasingly argue that sleep should be treated not as optional, but as a basic biological requirement for long-term health.