How Light, Exercise, and Sleep Fuel Your Metabolism

Dave Asprey, creator of the biohacking movement and Bulletproof Coffee, envisions a future in which we treat light like a drug, dimming it after dark in homes, stores, and airports. He imagines replacing harsh glares with gentle, supportive lighting, creating environments that align with our biology and support our health instead of disrupting it.

Asprey may be on to something. Metabolic health isn’t just about what’s on your plate. According to him, controlling his light exposure and syncing with natural cycles helped him restore his metabolism. By adopting simple habits such as sleeping in a pitch-black room and going outside first thing in the morning, he shifted from being a lifelong night owl to being an early riser—and he lost weight in the process, proving that lifestyle adjustments can have powerful effects.

“Habits form this foundational base work for our health, and it’s very hard to be healthy when you don’t have routines,” Dr. Halland Chen, a double board-certified physician specializing in longevity and metabolic health, told The Epoch Times.

“We’re in a very fast-paced world, and so the ability to eat right, sleep well, work out—it’s hard.”

When you understand how lifestyle factors influence your body, you can take simple daily actions that support metabolic health.

3 Simple Strategies

Natural light, sleep, and exercise can fine-tune your metabolism, reset your internal clock, and help you take control of your health. Dysregulation doesn’t happen overnight. Small, consistent habits form the foundation for long-term wellness, Chen said.

One key lifestyle factor that often goes overlooked is light exposure, a powerful metabolic signal.

1. Proper Lighting

Our bodies are hardwired to follow natural light cycles, yet modern living constantly disrupts them. Circadian rhythms, the body’s internal clocks that regulate metabolism, are highly sensitive to light. Understanding how both sunlight and artificial light affect your metabolism can help you harness the former while mitigating the latter.

“Natural light can actually stimulate your metabolism, and it does that through hormones, glycemic control, and enhancing insulin sensitivity,“ Dominic D’Agostino, a research scientist and professor at the University of South Florida, told The Epoch Times. ”In a way, it’s a form of metabolic therapy.”

Vitamin D, often called the sunshine vitamin, has receptors throughout the body, and low vitamin D levels are linked to metabolic dysfunction. Research shows that vitamin D deficiency is more common in people with higher body weight, likely because of a mix of biological and lifestyle factors such as reduced sun exposure and outdoor activity.

Humans have vitamin D receptors in the brain and on the skin. The skin can sense light, and it synchronizes hormones with a proper sleep-wake cycle, according to D’Agostino. Morning light can also reduce glucose levels and enhance insulin sensitivity.

“ I sleep in a room that is pitch black, and I go outside first thing in the morning,“ Asprey said. ”I connected my body to Mother Nature’s cycles.

“ If I had to choose between giving up natural sunlight and giving up whole foods ... I'd rather have the sun and ultra-processed food than ... no sun.”

At the opposite end of the spectrum is the artificial blue light that comes from devices, which can significantly harm our sleep and metabolic function by suppressing melatonin production. There’s no known safe level of exposure to artificial light at night. A 2024 study published in the Diabetes & Metabolism Journal found that nighttime artificial light exposure is linked to disrupted glucose metabolism and a higher risk of Type 2 diabetes.

A 2023 review published in Nutrients found that artificial light can disrupt natural cycles, affecting metabolism and daily routines. The authors concluded that adjusting light exposure or taking melatonin may help protect metabolic health, especially for shift workers or anyone with a misaligned circadian rhythm.

While blue light at night is disruptive, lights with longer wavelengths such as red or amber light are much less so. Asprey said dimming screens and shifting them to red or amber tones after sunset helped him reset his sleep schedule. He noted that using nighttime mode on your phone and dropping the screen brightness all the way down also make a difference.

“I’ve been a night owl my entire life,“ he said. ”I went to sleep at 2 a.m., and I could not change it to save my life until I learned how to control my light.”

Science supports these observations. A 2024 study published in the Journal of Biophotonics found that a single 15-minute session of red light therapy at 670 nanometers significantly lowered post-meal blood sugar levels in healthy participants, likely by improving mitochondrial function and increasing production of adenosine triphosphate—energy-carrying molecules found in all living cells—which uses glucose.

2. Exercise

“If you could put physical activity in a pill, it would be like a blockbuster drug that would work for everything,” D’Agostino said.

Chen noted that any physical activity is better than none. Simply moving your body is important because once you start one habit, it leads to another.

“Whenever you’re going to do it, I think your workout should be based on your sleep chronotype,” Chen said. This can make exercise feel easier and more sustainable. Night owls may prefer evening workouts, while early birds may do better in the morning.

Your chronotype, or body’s natural sleep-wake pattern, influences metabolism. Aligning habits with your internal clock can help you maintain healthy routines.

Research shows that people who are more sedentary face a higher risk of metabolic disorders, cardiovascular disease, and premature death. Limiting sedentary behavior may help prevent such outcomes.

Extended periods of sitting trigger cellular processes that contribute to metabolic disease, while low-intensity, nonexercise activity such as standing or moving intermittently throughout the day offers unique metabolic benefits that structured exercise alone cannot replace.

Frequent, short activity breaks during sedentary periods may even better protect metabolic health than a single continuous bout of exercise in healthy adults.

More sedentary time and less low-intensity activity are linked to higher waist circumference and overall metabolic risk, independent of moderate-to-vigorous exercise. Very low muscle mass is also a risk factor for insulin resistance.

Muscle quality matters, too.

“You see the cross-section MRI studies of people’s thighs, especially as people age, and you see those white streaks forming through the muscles,“ Urban Kiernan, who holds a doctorate in bioanalytical chemistry, told The Epoch Times. ”It’s not supposed to look like Wagyu beef.”

Research supports Kiernan’s observation. Higher intramuscular fat is linked to metabolic syndrome. Regular physical activity helps preserve muscle quality by reducing intramuscular fat and maintaining strength.

3. Quality Sleep

While you sleep, your body repairs and regulates itself. Without enough rest, hormones fall out of balance, driving a cycle of metabolic stress.

A dearth of sleep causes metabolic dysfunction, according to Chen.

“You’re eating more carbohydrates as a stress response because your body’s also having higher cortisol levels,“ he said. ”Cortisol affects insulin levels, which is one of the regulators of sugar. And so you get into this dangerous cycle of, ‘I need more carbs because my body’s in stress.’”

Even one night of partial sleep deprivation can cause insulin resistance in healthy people.

Asprey noted that the skin has photoreceptors that can detect light. For this reason, he said, wearing an eye mask while sleeping isn’t a satisfactory solution, and a pitch-black room is essential.

Asprey shared one step he takes to improve his sleep.

“Unplug or put black tape over every single LED in your bedroom—even that little blinky green light on your smoke detector,” he said.

A July study published in Nutrients suggests that sleep’s primary purpose may be a metabolic one. The authors proposed that individual sleep needs are tied to a person’s mitochondrial function, noting that a strong feeling of tiredness is a common symptom of human mitochondrial disease. They drew parallels between the brain’s regulation of sleep and its regulation of hunger. Both sleep and hunger are influenced by the same neural processes, pointing to a shared mitochondrial origin for sleep pressure: your body’s drive to sleep, which intensifies the longer you stay awake.

“It used to be a badge of honor to sleep five, four hours,“ Chen said. ”Now, it’s like you’re not tough for doing that.”