Cortisol
Episodes
Derek from More Plates More Dates joins Dr. Rhonda Patrick to discuss testosterone optimization.
In this clip, Dr. Martin Gibala delves into the nuances of sex-based differences in exercise response and their implications for individual outcomes.
Dr. Martin Gibala discusses HIIT's health benefits and describes common HIIT protocols.
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Derek from More Plates More Dates joins Dr. Rhonda Patrick to discuss testosterone optimization.
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In this clip, Dr. Martin Gibala delves into the nuances of sex-based differences in exercise response and their implications for individual outcomes.
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Dr. Martin Gibala discusses HIIT's health benefits and describes common HIIT protocols.
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In this clip, Dr. Matthew Walker explains how altering the timing and duration of daytime light exposure influences sleep.
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Dr. Rhonda Patrick describes how bright light exposure drives cortisol release.
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Dr. Matthew Walker discusses how anxiety affects sleep and identifies ways to manage that stress to improve sleep.
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Dr. Matthew Walker explains how altering the timing and duration of daytime light exposure influences sleep.
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Dr. Aubrey de Grey discusses technologies that can repair the various types of damage that occur during the aging process.
Topic Pages
News & Publications
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Childhood obesity is a growing concern with multiple contributing factors, and perhaps, exposure to artificial light at night is among the most important. To investigate this, researchers in China followed more than 218,000 schoolchildren over a 15-year period.
Each year, the students underwent health examinations that included body mass index measurements. At the same time, satellite data provided yearly measurements of how bright the outdoor night sky was in the area around each school. Children were then grouped based on long-term trends over the study period: areas that stayed consistently bright, areas that brightened slowly, areas that brightened rapidly, and areas where brightness declined. Because the rapidly brightening pattern had the lowest baseline light, it served as the reference group for all comparisons.
The study revealed distinct differences across the light exposure groups:
- Children attending schools in areas that stayed consistently bright had the highest risk. Boys had a 67% higher rate of becoming overweight or obese, and girls had a 56% higher rate.
- In areas that brightened slowly, the risk was elevated but not statistically significant.
- Areas where brightness declined showed no meaningful difference from the reference.
- Among children who began at a normal or low weight, the consistently bright group recorded 9.95 new cases of overweight or obesity per 1,000 person-years, compared with 6.10 in the rapidly brightening group and 8.04 in the slowly brightening group.
- On a population level, long-term exposure to consistently bright night-time environments accounted for about 40 percent of the risk in boys and 36 percent in girls.
Prolonged exposure to artificial light disrupts circadian rhythms, the internal clocks that regulate daily cycles of hormones such as melatonin and cortisol. When these rhythms are disturbed, appetite, metabolism, and fat storage can be affected in ways that promote weight gain. Another possible mechanism may involve brown fat, a tissue that normally burns energy to generate heat but may become less active under constant night-time light. The differences between boys and girls may reflect a mix of biological sensitivity and behavioral factors such as screen use. Finally, the stronger risks in the consistently bright and slowly brightening groups may point to the impact of longer cumulative exposure, whereas more recent increases in brightness, as in the rapidly brightening group, may not have had the same effect.
Conclusion:
Children who attended schools in brighter night-time environments were more likely to gain excess weight over the school years. The study was limited because light levels were estimated from school locations, not individual homes, and detailed information on diet, activity, or puberty was unavailable. Moreover, while the analysis adjusted for broad regional differences, it cannot be ruled out that environmental and socioeconomic changes occurring alongside rising night-time light influenced the results. Still, the findings highlight night-time light as a potential and under-recognized factor in childhood overweight and obesity. Learn more about how to improve sleep in episode #45 featuring Dr. Matthew Walker. -
Sleep loss and lower sleep duration may be associated with lower morning, afternoon and 24-h testosterone levels. (2022) link.springer.com
From the publication:
When epidemiological and interventional studies are considered collectively, sleep loss and lower sleep duration are associated with lower morning, afternoon and 24-h testosterone; as well as higher afternoon, but not morning or 24-h cortisol. These reciprocal changes imbalances anabolic-catabolic signaling because testosterone and cortisol are respectively the main anabolic and catabolic signals in man. Fixing testosterone-cortisol balance by means of a novel dual-hormone clamp mitigates the induction of insulin resistance by sleep restriction and provided the first proof-of-concept that the metabolic harm from sleep loss can be ameliorated by approaches that do not require sleeping more. Obstructive sleep apnea is associated with lower testosterone, even after controlling for age and obesity whereas the conclusion that continuous positive airway pressure therapy has no effect on testosterone is premature because available studies are underpowered and better-quality studies suggest otherwise. High dose testosterone therapy induces OSA [obstructive sleep apnea], but more physiological dosing may not; and this effect may be transient or may dissipate with longer term therapy.
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Large doses of vitamin C might mitigate the body's stress response, thereby improving immunity. www.sciencedaily.com
The human body responds to mental stress by releasing hormones called corticosteroids, triggering the body’s fight or flight response. Chronic activation of these hormones can impair immune function, increasing susceptibility to infection and disease. Findings from an early study in mice demonstrate that vitamin C mitigates the body’s stress response, thereby improving immunity.
The authors of the study immobilized mice for an hour every day for three weeks to induce stress. They also fed the mice 200 milligrams of vitamin C daily – roughly equivalent to several grams per day in humans. A control group of mice also received vitamin C but they were not subjected to stress.
The stressed mice that received large doses of vitamin C in their diets exhibited fewer signs of stress as evidenced by lower levels of corticosteroid hormones as well as other physical manifestations, such as weight loss. The mice also exhibited higher levels of IgG, the most abundant antibody in circulation, responsible for binding a broad selection of pathogens, including viruses, bacteria, and fungi, to prevent infection. Interestingly, the non-stressed mice that received large doses of vitamin C exhibited even greater increases in IgG, suggesting that stress cancels out some of the beneficial effects of the vitamin.
These findings suggest that high dose vitamin C might improve immune function, especially during times of mental and physical stress.