Circadian rhythms have a dramatic impact on health, weight, mental well-being, and immune system. Over a hundred drugs have a known time of day effect.

Circadian rhythms influence every aspect of physiology and behavior. The master clock in the brain coordinates the rhythmic behavior of billions of individual cellular clocks throughout the body.

The light-dark cycle is the most important signal for setting the internal molecular clockwork. A third photoreceptor within the eye, a photosensitive retinal ganglion cell, is directly light sensitive and projects to the master clock within the brain.

Russell Foster faced skepticism when proposing the existence of another receptor within the eye, but through perseverance and better experiments, he convinced the world in 1999.

Ignoring circadian rhythm can lead to emotional fluctuations, cognitive impairment, health issues, and long-term problems like cardiovascular issues, lowered immunity, metabolic abnormalities, and worsened depression and psychosis.

Russell Foster and Jonathan Wolff discuss the impact of sleep and circadian rhythm disruption, particularly for night shift workers. They emphasize the double whammy of being on night shift, where the body's response is to over-activate the stress axis to function, leading to poor sleep quality and duration during the day.

They highlight the risks associated with night shift work, such as decreased vigilance leading to safety concerns, and the potential for poor physical and mental health. They suggest practical solutions like vigilance devices, increased workplace lighting, and providing healthier snacks for night shift workers.

The conversation delves into the profound consequences of working against the body clock, including higher divorce rates for night shift workers and the impact on the immune system. They also touch on the importance of stable circadian sleep-wake timing for long-term survival in cancer patients.

The empirical evidence shows that glucose clearance is much more efficient during the first half of the day and becomes pretty inefficient towards evening, leading to glucose intolerance and type 2 diabetes.

Experiments have shown that loading calories at breakfast and lunchtime promotes more effective weight loss compared to loading calories at lunchtime and evening.

Our changed eating habits, with large meals in the evening, are a recent occurrence driven by aristocrats, and it's the worst possible thing we could be doing. The recommendation is to have a big breakfast, a nice lunch, and a minimum meal in the evening.

Experiments on metabolism have mostly been done on healthy young males, so it's important to consider the implications for the rest of society, including females.

There's not much research on the long-term effects of disrupted circadian rhythms due to small children waking up at night. It's crucial to establish a robust sleep-wake structure for young children, focusing on dark bedrooms, the right temperature, and a clear routine.

Russell Foster emphasizes the importance of the body clock and the negative outcomes of living outside of its setting, especially for night shift workers.

Aging can lead to a decline in the circadian rhythm, and women going through menopause experience significant disruption of sleep due to hormonal changes.

The conversation highlights the personalized nature of sleep and the need to embrace it, with Russell Foster emphasizing that different sleep patterns don't have to be bad.