The practice of fasting has often made headline news in recent years. For many of us, it is a relatively new concept, and while some of us have adopted it as a way of life, others consider it no more than a passing fad. So, what should we think of it? What does the research tell us? Here, we set out to look at the evidence for fasting and share with you our thoughts on why you may choose to fast.
For many cultures, fasting is a centuries old tradition, often associated with religious and spiritual practice and considered integral to health and well-being. Fasting and calorie restricted lifestyles are also common practices in geographic regions of the world where people live significantly longer than average. These regions are commonly referred to as the ‘bluezones’.
Scientific research consistently demonstrates extreme calorie restriction (of around 25-50%) significantly extends the life-span of a variety of animal species – with the implication that the same might be true for humans. Despite these impressive results, permanently reducing calorie intake with such severity is likely to be neither enjoyable nor sustainable for most of us! Nonetheless, it is in part a consequence of these remarkable studies, that scientists have started looking for other ways to achieve the same effect.
In the early 20th century, fasting was common practice in the UK, and used as part of the ‘nature cure’ approach (which also included fresh air and exercise!) to address multiple health conditions. Gradually, as society moved towards medical rather than natural intervention, the nature cure approach died out. But now we find, interest in fasting revived in the UK, and this is almost solely due to the popularity of the 5:2 diet; an eating pattern where calorie intake is substantially reduced two days a week.
The 5:2 diet is based on intermittent fasting and involves alternating between periods of eating and periods of fasting. In the 5:2 diet, calorie intake is restricted to 500-600 calories on the 2 days, with normal calorie intake on the remaining 5 days. Another form of intermittent fasting gaining popularity is Time Restricted Feeding. This variation on the fasting theme limits your food intake to a certain number of hours each day. For example, you may fast over-night, for between 13-16 hours, and restrict eating to the remaining hours of the 24 hour cycle.
So, looking at the research, what does it say? Is fasting a fad or might it be the elixir of life? Given the popularity of the 5:2 diet, there are surprising few studies on it but, on the bright side, there is a large body of research to support the health benefits of fasting in general. Although most of this research has been conducted on animals, the results are promising, and further studies are underway. Beyond being an impressive weight loss tool, it’s suggested intermittent fasting may improve a range of health bio-markers including; insulin resistance, oxidative stress, and inflammation. Studies also suggest fasting can preserve learning and memory function. Put together, there is a picture emerging that intermittent fasting may be an effective way to reduce our risk of ageing-related disease.
In recent years, researchers have also been looking at how fasting may be of benefit to people with cancer. To date, most of the research has been conducted on animals, with only a handful of preliminary human studies having been undertaken. Nonetheless, these early results are promising. Several studies have investigated the effect of short-term fasting on the efficacy of chemotherapy. The results show that short-term fasting (defined as no food or calorific drinks for between 48-72 hours before chemotherapy) may reduce chemotherapy side effects, as well as suppress tumor progression, both growth and metastases. Other studies have demonstrated that fasting can enhance the effectiveness of radiotherapy. There are many possible mechanisms at play but one popular theory is that when normal cells are deprived of nutrients, they appear to be protected from the effects of chemotherapy and radiotherapy. While, in contrast, cancer cells appear to be more susceptible to ‘attack’.
Another interesting study – involving over 2000 women – looked at whether the duration of nightly fasting (a form of time restricted eating) could change breast cancer prognosis. Once again, the results were very promising and showed that prolonged night fasts of 13 hours or more, reduced the risk of breast cancer recurrence in women.
It’s important to know that fasting is not suitable for everyone. Those with an existing medical condition, such as diabetes, heart or liver disease, or cachexia should not fast. If you are undertaking chemotherapy and would like to consider fasting alongside, we recommend you speak with your Oncology team before doing so. If you do choose to fast, remember to stay hydrated and take plenty of rest during your fasting period. And when you are eating, be sure to eat nutrient dense foods!
If you are completely new to fasting, why not start with a 12-hour nightly fast, as a gentle introduction? So, for example, you may choose to eat only between the hours of 8am and 8pm. This is considered a normal approach to healthy eating since it allows the digestive system time for rest and recovery.
So, it seems the scientific research emerging in recent years supports the use of fasting in the quest for better health, as well as demonstrating positive use in cancer. Whilst this is still a relatively new area of research, requiring further clinical studies, here at Penny Brohn, we are excited about these early results and we will be following future research with great interest.