The Hidden Link Between Low-Carb Diets, Cold Exposure, and Light: What Ancestral Metabolism Can Teach Us
- Mobility-Fitness.com
- 4 days ago
- 6 min read
Our ancestors never ate in isolation — their diets evolved with the seasons. When food sources turned low-carb, the environment turned cold and dark. Today, many follow low-carb diets in warm, blue-lit environments, creating a mismatch that affects metabolism, hormones, and sleep.
In the modern technology era, in some diet cultures, we still hold on to our "ancestral" diet structures, but fail to consider the other metabolically important factors that ancestrally would accompany our diet "choices".
When nature's providing traditionally fell into the low carb category — less fruit and vegetables, more weight on animal-based foods such as meat and dairy — was during the months of low UV and short daylight hours.
For our physiology, simply put, this means more melatonin, less cortisol, and more brown fat activation, less relying on thyroid gland for metabolic regulation. Humans, like many mammals, are photoperiodic — our metabolism naturally shifts with changes in day length and light exposure (1,2). This seasonal rhythm influences thyroid output, leptin sensitivity, and even appetite (2).
How Cold Exposure Activates Brown Fat and Boosts Metabolism
Cold exposure activates brown fat, leading to desirable metabolic outcomes (4). It does so by upregulating DIO2, which converts inactive T4 into active T3, supporting local thermogenesis (3). Brown fat is mitochondria-dense, and when activated, increases metabolic rate and glucose uptake (4). These metabolic adaptations would have been critical in ancestral cold environments, allowing humans to maintain energy balance and stable blood sugar levels even when carbohydrate intake was low. Sustained cold exposure promotes mitochondrial turnover and β-oxidation in brown adipose tissue, enhances its oxidative capacity, and supports efficient non-shivering thermogenesis (5,6,7) As an environmental cue, cold stress creates a markedly different metabolic environment compared to a temperature-regulated setting. In ancestral environments, this may have facilitated a greater reliance on fat-based, lower-carbohydrate energy sources; by contrast, our modern, temperature-controlled living conditions may limit these adaptive responses, potentially reducing the effectiveness of low-carb dietary strategies.
How Light and Darkness Shape Hormones and Metabolic Balance
Infrared Light and Mitochondrial Energy
At sunrise and sunset, when the sun is low on the horizon, shorter wavelengths like UV and blue light are largely scattered, and the spectrum is dominated by red and near-infrared light (~600–1000 nm). This means the relative proportion of infrared light is higher during these times. Longer periods of darkness increase pineal melatonin production. Meanwhile, infrared light can enhance mitochondrial function by stimulating cytochrome c oxidase (CCO), boosting cellular energy (ATP) production and supporting repair processes. Mitochondria also synthesize melatonin locally, contributing to antioxidant defenses and potentially aiding cellular repair cycles (8).
Melatonin: The Forgotten Metabolic Regulator
In ancestral environments, shorter daylight hours and reduced exposure to high-energy (blue) light during winter months would have naturally lowered daytime cortisol peaks (1,9). This seasonal pattern likely supported metabolic flexibility, favoring fat oxidation over carbohydrate metabolism when food was scarcer and energy demands shifted. In modern environments, however, artificial lighting and nighttime exposure to blue-enriched light often disrupt these natural rhythms. Such exposure suppresses melatonin and can elevate cortisol and glucose at inappropriate times, effectively sending a daytime signal during the night (9,10). Over time, this misalignment may impair the body’s circadian metabolic signaling, potentially influencing substrate utilization and the efficiency of fuel use.
Modern Lifestyle vs. Ancestral Metabolism: The Circadian Mismatch
Modern environment however, is devoid of temperature changes throughout the year, and enjoys a blue-enriched environment of light throughout the day. This translates to lack of red/near-infrared light, potentially reducing mitochondrial support for cellular repair (8). And lack of complete darkness after sunset, translating to impaired release of pineal melatonin, thus disturbed melatonin–cortisol cycles (1,9), consequently impairing tissue oxygenation and fatty acid oxidation.
In a low carb diet situation, this mismatch requires more gluconeogenesis to turn amino acids into glucose, increasing metabolic strain. Cold and low light were originally cofactors in the low-carb environment — without them, the body’s hormonal and mitochondrial signals may be out of sync (3,4,8).
Today, many follow low-carb diets while living in an environment opposite of winter: constant warmth, artificial blue light, and disrupted circadian rhythms. This mismatch may explain why some experience fatigue, poor sleep, and metabolic disruption on low-carb diets (9,10).
Recreating Ancestral Conditions for Optimal Metabolic Health
So, can we assume that just because it's winter, we can keep thriving with the same diet our ancestors consumed? Or does it mean we need to shift our own environment to match nature's cycles first — with intermittent cold, infrared light (fire light), complete darkness at night — and low carb diet?
Or are we living in a "equatorial environment" with constant comfortable temperature, with a disturbed 24-hour high-energy light environment (LED lights, screens, phones, etc.), and expecting a good response from our "ancestral low carb diet"?
Geography also matters. Equatorial populations evolved under year-round UV exposure and stable light cycles, thriving on carbohydrate-rich diets. In contrast, higher-latitude populations adapted to long periods of darkness, cold, and fat-based energy sources. The ancestral success of any diet was thus tightly linked to latitude, temperature, and photoperiod (2).
In a world of "advanced tech", we need to become advanced thinkers too.
Perhaps the success of any diet depends less on macronutrients alone, and more on the context of light, temperature, and circadian alignment in which it’s practiced. True ancestral health means reuniting food with its natural environmental companions.
Key Takeaway:
Modern low-carb diets often miss two ancestral partners — cold and darkness. When aligned with natural light and temperature cycles, metabolism works more efficiently through improved brown fat activation, melatonin regulation, and mitochondrial repair. While adaptation to low carb diets have been a "survival response" by the body in times of long dark months, in the modern environment chronic low carbohydrate diets may not always support our biology, and should always be approached with individual and context dependant considerations.
Frequently asked questions:
Q: Why does cold exposure improve metabolism?
A: Cold activates brown fat, increasing energy use and heat production while supporting thyroid and leptin function.
Q: How does light exposure affect low-carb metabolism?
A: Bright blue light raises cortisol and glucose, while darkness increases melatonin and fat oxidation — aligning diet with light cycles supports balance.
Q: Why do some people feel fatigued or cold on a low-carb diet?
A: When carbohydrate intake drops, the thyroid gland naturally reduces output, and the body relies more on fat oxidation for energy. Without the ancestral companions of cold exposure and natural darkness, modern low-carb diets can disrupt hormonal and mitochondrial balance — leading to fatigue, poor sleep, and slower metabolism.
Q: How can I align my modern lifestyle with ancestral metabolic rhythms?
A: Focus on environmental cues — not just macronutrients. Get daily sunlight exposure, minimize artificial blue light after sunset, sleep in total darkness, and introduce brief cold exposure (like cool showers or outdoor walks). These signals help synchronize your circadian rhythm, support thyroid and mitochondrial function.
Realign your body with nature's clock - thrive in any season
The Circadian Reset Protocol helps you align your body with natural light and temperature cues, supporting hormones, energy, and metabolic health. → Start your Circadian Reset today
Explore more about circadian health in our related post on blue light and melatonin →
References:
1. Wehr, T. A., et al. (1991). The durations of human melatonin secretion and sleep respond to changes in daylength (photoperiod).
Proceedings of the National Academy of Sciences, 88(17), 8646–8650.
2. Navarro-Masip, È., et al. 2023. Photoperiodic remodeling of adiposity and energy metabolism in non-human mammals. Frontiers in Physiology, 14, 1097527.
3. de Jesús LA, Carvalho SD, Ribeiro MO, Schneider M, Kim SW, Harney JW, Larsen PR, Bianco AC. The type 2 iodothyronine deiodinase is essential for adaptive thermogenesis in brown adipose tissue. Journal of Clinical Investigation. 2001;108(9):1379–1385.
4. van Marken Lichtenbelt WD, Vanhommerig JW, Smulders NM, Drossaerts JM, Kemerink GJ, Bouvy ND, Schrauwen P, Teule GJ. Cold-activated brown adipose tissue in healthy men.
New England Journal of Medicine. 2009;360(15):1500–1508.
4. Virtanen KA, Lidell ME, Orava J, et al.
Functional brown adipose tissue in healthy adults.
New England Journal of Medicine. 2009;360(15):1518–1525.
5. Yau WWY, Wong KA, Zhou J, et al. Chronic cold exposure induces autophagy to promote fatty acid oxidation, mitochondrial turnover, and thermogenesis in brown adipose tissue. iScience. 2021;24(5):102434.
6. Blondin, Denis P., et al. "Increased brown adipose tissue oxidative capacity in cold-acclimated humans." The Journal of Clinical Endocrinology & Metabolism 99.3 (2014): E438-E446.
7. Mast H. Fatty acid oxidation: a neglected factor in understanding the adjustment of mitochondrial function to cold temperatures. Journal of Experimental Biology. 2022;225(21):jeb244934.
8. Reiter, R. J., et al. 2018. Mitochondria: Central Organelles for Melatonin’s Antioxidant and Anti-Aging Actions. Molecules, 23(2), 509.
9. Figueiro, M. G., et al. (2010).
The effects of red and blue lights on circadian variations in cortisol, alpha amylase, and melatonin.
International Journal of Endocrinology, 2010, 829351.
10. Cheung, I. N., et. al. 2016. Morning and evening blue-enriched light exposure alters metabolic function in normal weight adults. PLOS ONE, 11(6), e0157649.
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