Fasting and the Circadian Rhythm

Dr Satchin Panda, a leading researcher in the field of Circadian Biology, has extensively researched the effect on people who don’t follow their circadian rhythm -- most people, it would appear! The circadian rhythm is a natural process internal to humans that regulates the sleep/wake cycle (and others) and repeats approximately every 24 hours.

Even a short disruption in sleep can result in some discomfort — think about this for yourself; you feel sleepy but can’t, your stomach may be upset, your muscles may be weak and your mind foggy. Research on study participants who were sleep-deprived demonstrated they ate more and made poorer food choices. Imagine the health consequences for shift-workers and new mothers? In a 2013 analysis of published papers on the topic, researchers found children of shift-workers not only had more cognitive and behavioural problems than children raised by non shift-workers; they also had a higher incidence of obesity.

It has been well documented that shift-workers experience more health problems than non shift-workers, particularly gastrointestinal diseases, obesity, diabetes and cardiovascular disease.

Panda believes we are all shift-workers to some extent and need to find how our circadian clock works to optimise our health.
The science research world largely discounted the field of circadian biology until the mid 1970s. From then onwards various studies using plants, insects, animals and ultimately humans have demonstrated a very strong adherence to circadian rhythms for all life on earth. An early study had one man placed in a cave in the Andes with sufficient food, candles and reading material to keep him occupied for weeks. The study revealed his sleep/wake cycle continued with clock- work precision for several weeks in the cave. His cycle was 24 hours and 15 minutes.

Strong circadian rhythms optimise biological function.

The Suprachiasmatic Nucleus (SCN), a cluster of small cells based in the hypothalamus, is the master clock directing our circadian rhythms. The hypothalamus is also the command centre for hunger, satiety, sleep, fluid balance and the stress response.

Panda argues, with much supporting evidence that disrupting this clock too much plays havoc with our metabolic rhythm. If our internal ‘canteen’ is open for say 18 hours a day, our digestive system becomes less efficient; gastric juice and gut hormones are produced at a different rate and you may experience indigestion/acid reflux. Every time we eat the fat-burning programme gets switched off and fat will be stored. This may be why diets don’t work for some people.
Set an eating routine and stick to it! Physical activity is proven to assist with good sleep.

Set your clock for weight loss

Experiments using mice and restricting their time for eating had amazing results, establishing the idea that it not only what you eat but when you eat that matters, especially for long term health. The mice whom were allowed an eight-hour eating window but were fed the same high fat high sugar diet (normally causes them severe metabolic disease) were protected from disease; they didn’t gain excess weight, they had normal blood sugar and cholesterol levels.

A Spanish /American study with humans found that individuals who spread their calories over a longer period of time did not lose weight. However people who ate bigger meals during the day and refrained from eating at night lost a substantial amount of weight. Our brain clock is responsive to light but the clocks in the gut, liver, heart and kidneys respond to food. If we keep changing our routine the clocks get confused.

Panda set up a study where participants who had previously reported eating in a 14 hour or more window and were overweight, were to choose the same 10 hour window in which to eat. What they ate didn’t change. In four months all participants lost an average of 4% body weight. They also reported sleeping better at night, and feeling more energetic and less hungry during the day.

The optimal eating window appears to be between 8 and 11 hours — the health benefits improve with the shorter eating window. Also, maintaining a strict schedule was less damaging. Panda also advocates eating early and finishing eating early. Drinking water anytime didn’t appear to impact on the body’s ability to repair and rejuvenate.

Whilst Panda has demonstrated that people will lose weight using Time Restricted Eating regardless of what they eat, he does recommend eating healthy wholefoods!

The Circadian Code, Satchin Panda (Vermilion Books, 2018)
The Hungry Brain, Stephan J. Guyenet (Vermilion Books, 2017)