The concept of the body clock, an internal biological mechanism that regulates body temperature, sleep, metabolism and hormone levels is a familiar one to most of us. You may have experienced the consequences of a temporary mismatch between your external environment and your own biological rhythm when you fly overseas to a different time zone. There is that short period where our wellbeing is affected as our body adjusts to a new biological rhythm.
However, the impact of consistently ignoring our body clock has only recently been understood and is now recognised as having detrimental consequences that are long term, making us more susceptible to chronic diseases like obesity, diabetes and cardiovascular disease.
The idea of living in harmony with our internal body clock is the subject of much research and has given rise to the term ‘chronotherapy’ — treatment in alignment with circadian rhythms. New understanding of how our internal body clock works is being used to help with management of obesity and other chronic health issues.
Circadian rhythms
In 2017, the Nobel Prise for Medicine was awarded to three geneticists who discovered the gene that controls our normal biological rhythms and explains how our bodies adapt to the rotation of the earth every 24 hours. This gene, found in the hypothalamus, contains the mechanism behind the master body clock that regulates the circadian rhythms found inside every single cell of our body.
This carefully calibrated process is involved in the many physiological processes that allow our bodies to adjust and adapt to different times of the day. When it is functioning normally, this biological clock regulates our sleeping, eating, body temperature, blood pressure and the rise and fall of a range of hormones with different metabolic functions. However, our busy modern lives increasingly dissociate us from our internal body clock.
We often work late, eat irregularly, and use screen devices to relax late into the night. We override and ignore this delicate internal mechanism that is fundamental to our wellbeing. There are a multitude of disruptors of our circadian rhythm. They can include: shift work; irregular eating; alcohol and other drugs; screen devices; lighting; and eating late at night.
Time restricted eating
A particularly fascinating area of research is focused on chrono-nutrition, which looks at the impact of nutrition on metabolism-based circadian patterns. Studies focus on three aspects of eating: irregularity, frequency, and clock time. This has given rise to the concept of Time Restricted Eating, or TRE, when eating is limited to a certain number of hours each day.
One two-week trial found that consuming meals regularly, even over such a short period of time, has a positive impact on cardiometabolic risk factors with lower peak insulin and lower cholesterol — in both lean and in obese women. This has significant implications in a society where many of us snack irregularly for up to 16 hours per day. How often do you grab a coffee and something to eat at 7am only to collapse at 10pm with a glass of wine or a snack?
A great deal of the early research about Time Restricted Eating has been done by Dr Satchin Panda, Professor at Salk Institute for Biological Studies in San Diego, who has demonstrated the positive health benefits of eating three regular meals within a time-restricted framework.
Subjects who committed to TRE experienced positive outcomes including weight loss; better control of blood sugar; improved blood pressure and sleep quality; and a lowering of their cholesterol.
The beauty of adopting a TRE pattern is that it doesn’t matter too much what sort of diet you decide to follow. Whether you are committed to a plant-based diet, a keto diet, a low-fat or low-carb way of eating, it is easy to adapt each one so that you are eating in tune with your natural circadian rhythm.
Although the research often restricts eating to a very narrow window of eight to 10 hours, benefits are also achieved by eating within a 12-hour window.
It is helpful to look back a couple of decades and think about the way our grandparents ate. Most people then ate three meals a day, used minimal processed food, and did not snack in between meals.
Shift workers provide fascinating insights. Studies show a strong correlation between shift work and weight gain. Shift workers also have higher rates of chronic disease, including diabetes and heart disease. Even less than one week of working a night shift can have a negative impact on blood glucose levels and circulating insulin. In one study, it was interesting to note that when shift workers restricted food intake to daylight hours only, there was an overall positive impact, with a reduction in blood sugar levels and an improved work performance.
The New Zealand Health Survey 2020/21 found that 34 per cent of adults were obese, up from 31% in 2019/20. Excess weight is associated with many health conditions including type 2 diabetes, ischaemic heart disease, stroke, several cancers, sleep apnoea, osteoarthritis and reproductive abnormalities. As such, obesity places an enormous financial burden on the health system.
Links to obesity
It is unsurprising that there is intense interest in studying the relationship between circadian rhythms and weight management. Managing chronic disease nearly always includes a discussion about obesity, with patients eager to find a miracle cure amongst the huge range of diets and drugs on offer. The reality is that most patients lose a few kilograms — only to regain them, often with a few extra added on, in a familiar pattern referred to as yo-yo dieting. While the causes of obesity are complex and multifactorial, TRE offers an option that is without side effects, is not prescriptive or rigid and allows patients to eat a diet that suits their specific cultural and personal preferences.
As a GP, I have started to discuss TRE with patients who are struggling to control their diabetes or who have multiple risk factors for cardiovascular disease. There’s strong evidence to suggest that eating in tune with your biological clock improves chronic disease management with early indications that it can help with weight management.
I always advise them that TRE is not a licence to live on unhealthy processed food, but an invitation to focus not only on when you eat but to make better choices about what you eat. I have had success with several patients who find TRE straightforward to follow and adapted the recommendations to suit their lifestyle.
One patient, Jess* had gained a significant amount of weight after being treated with an antipsychotic medication for her bipolar disorder. She was subsequently diagnosed with type 2 diabetes and feeling quite despondent. I discussed TRE with her, and she opted to give it a go, together with her husband whose weight was also in the obese range. She had a session with our diabetes educator and opted for a lower- carbohydrate diet which was beneficial for managing her blood sugar levels. We recorded all her baseline statistics — her diabetes control, blood pressure, cholesterol, and her BML
It was so rewarding to see her progress over three months. Her long-term blood sugars dropped to the normal range, I was able to cease her blood pressure medications, her cholesterol improved, and her BMI dropped from the obese to the overweight range. She found it straightforward to eat within a 12-hour window and her cholesterol, diabetes control and blood pressure readings continue to improve even now where her weight loss has slowed.
Her husband Bill has also lost a significant amount of weight and is motivated to continue this style of eating. They are both walking regularly and sleeping much better. Jess confided to me that Bill is no longer snoring and is hoping to be able to come off his CPAP machine at night.
There is growing interest in chrono-nutrition, with studies underway around the world. The emerging evidence certainly shows a correlation with mistimed/erratic eating and an increase in obesity and cardiometabolic diseases, such as heart attack, stroke or diabetes.
The evidence in mice is very strong that irregular and frequent snacking can have significant impacts on overall health. While the human studies are ongoing, it is reasonable to adopt a way of eating that appears to yield such significant benefits without any risk of the harms often associated with other strategies trialled for managing obesity-related chronic diseases.
It is beneficial not only for those who are obese or suffering from chronic disease but for anybody interested in living in tune with their internal biological clock and maximising their overall health and wellbeing.
*Name changed for confidentiality
