Circadian Heliotherapy
You've read the threads. You've tried the supplements. You've tracked your sleep with three different devices and you still wake up tired. The problem isn't effort. It's order of operations. A small number of circadian inputs drive the majority of your health outcomes. This course identifies those inputs and sequences them correctly.
A structured look at the circadian system, the light environment, sleep, and metabolic timing.
"My body fat dropped from 29% to 23% and I'm continuing to make progress. My sleep and consistency are way better now."
A clearer picture of what the 80/20 Circadian Course covers and how to get started.
It is for people who want to understand how circadian biology, light exposure, sleep, and meal timing relate to human health—and how to apply those principles in everyday life.
The curriculum is organized around four areas: the circadian system, the 80/20 light rules, sleep and circadian timing, and metabolism and fat loss.
The course focuses on a small number of high-impact environmental and behavioral inputs, then explains how to sequence them through the day.
The course begins with the foundations of the circadian system and builds from there, connecting the underlying biology to practical daily inputs.
The course is available through Stan Store for a one-time purchase of $197. Use the enrollment link to view the course page and complete your purchase.
A different way to understand skin through circadian biology and photobiology.
Explore how light, biological timing, and the body's own regulatory systems shape skin function. Built for estheticians ready to look beyond surface-level protocols and understand the science behind skin health.
Explore Rethinking Skin
For estheticians who want to bring a deeper understanding of circadian biology, sunlight, and skin physiology into their work.
View course details
Zaid K. Dahhaj · Circadian Biology Educator
Understand your biology. Restore your relationship with nature.
I’m Zaid K. Dahhaj, a circadian biology educator focused on the relationship between light, biological timing, and human physiology.
I translate primary literature across circadian biology and photobiology into practical education—helping people understand how daily light exposure, darkness, sleep, and meal timing interact with the body's internal clocks.
At the center of my work is a simple idea: human biology evolved in relationship with the natural light-dark cycle. Modern environments often obscure those signals. My work explores what the science says, and how to bring those environmental inputs back into everyday life.
Explore my writing"My health is already improving applying the knowledge. Big early change is visual acuity. If I ever practice my integrative sports medicine again it will be a circadian centered practice."
"Working with Zaid changed how I think about my health entirely. Optimizing my circadian rhythm and light environment shifted my energy, my sleep, and my body composition from upstream inputs I had been ignoring."
"I sleep like a baby now. My deep and REM sleep improved dramatically, my metabolism feels like a furnace, and I have steady energy all day without stimulants."
"Within two weeks I dropped a full pants size and started sleeping much better. I finally have the daytime energy to get through everything I need to do."
"My body fat dropped from 29% to 23% and I'm continuing to make progress. My sleep and consistency are way better now."
"My afternoon slump vanished and sleep got fixed. One of the best courses to fix your circadian rhythm. Now I understand why he didn't give a big list of supplements."
Conversations on circadian biology, light as medicine, health sovereignty, and the primary literature that changes how people understand their own bodies.
Learn the principles of circadian biology and understand the environmental inputs that shape human physiology.
For media appearances, interviews, and collaborations, connect with me directly.
Last Updated: September 25, 2026
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Last Updated: September 25, 2026
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