Part 1 of 3: What is fasting and why would you consider it?
With the New Year upon us we will all soon be inundated with information on choosing the best diet to help us shed unwanted pounds and improve our health in 2020.
As a registered dietitian here at Synchronicity I have made a career of understanding the science of how food impacts our heath. I believe in sharing nutrition information that is supported by quality research. So, for the next month I am choosing to focus our nutrition blog on a growing body of research that is demonstrating the incredible health benefits of both fasting and time restricted feeding. In this week’s post I’ll detail the benefits of fasting and clear up some common definition problems. In the weeks that follow we’ll review what happens during fasting and time restricted feeding and then we’ll dig into how to make it work in your life.
What are the benefits of fasting that are supported by research?
The take home message here is simple, a periodic absence of energy intake may improve risk factors for disease while promoting repair and stress reduction in the body. If your body is not always busy digesting, it can spend more energy on rebuilding and repair while also reducing the exposure to the oxidative stress that naturally occurs during metabolic activity. Research backed benefits include:
- Autophagy (a process of clearing out damaged cells)
- Reduced inflammation
- Reduced oxidative stress (which translates to a reduced rate of cellular aging
- Increased production of detoxification enzyme
- Increased expression of Brain Derived Neurotrophic Factor in neurons (BDNF is miracle grow for the brain)
- Increased serotonin
- Increased resistance to stress
- Improvement in bio-markers of disease such as
- Insulin sensitivity
- Pro-inflammatory markers
What medical conditions has fasting been shown to benefit?
- Rheumatoid arthritis
- Chronic pain
- Heart disease
- Used in conjunction for those undergoing chemotherapy treatments. (Cancer cells do not have the protective mechanism normal cells have that are activated during a fast and therefore cancer cells are harmed by the lack of glucose and energy intake).
How about one more HUGE benefit?
Fasting may also promote longevity and significantly slow down the aging process! During a fast, a reduction in the insulin-like growth factor (IGF-1) is observed. High levels of IGF-1 are associated with aging and the development of cancer. Animal studies have shown that by lowering this hormone, life can be extended.
Does fasting help with weight loss?
Yes. Caloric restriction has long been known to influence both weight and fat loss. But it may be the long-term physiologic adaptations that result from voluntary fasting that produce the most significant and sustainable benefits.
According to a review article in The New England Journal of Medicine, much of the benefit attributable to fasting is due to the metabolic switching that occurs during a fast as the body switches from glucose utilization for energy to fat utilization. This adaptation activates various pathways and cellular responses that have shown to benefit human health. In a chronic fed state however, insulin levels stay elevated and the body is in storing rather than burning mode making weight loss challenging.
While there are clear short-term weight loss benefits associated with fasting, it is the long-term adaptations where sustainable benefits exist. Long-term physiologic adaptations include increased fat metabolism, a reduction in abdominal fat, improvement in insulin sensitivity and glucose utilization, and improvement in the gut microbiome which may influence metabolism.
Simply put, the research supports the idea that periodic fasting can improve the body’s ability to use fat for fuel, increase weight loss, and promote long term health.
Key definitions: Fasting, intermittent fasting, and time restricted feeding (TRF)
Intermittent fasting and fasting in general is a form of calorie restriction for a specified span of time. This differs from time restricted feeding (TRF) with which more people are familiar.
Fasting can take on many various forms. Two fasting methods frequently seen in research studies are “alternate day fasting”, and 5:2 fasting. The alternate day fast alternates one day of low-calorie intake, up to 500 kcal, followed by a day of unrestricted eating. The 5:2 method follows a very low-calorie diet, up to 500 kcal, 2 days per week and normal eating for 5 days. Physiological benefits have been reported with both methods.
Time restricted feeding (TRF), on the other hand, (which is often mistakenly referred to as intermittent fasting) is a process of compressing all calories into a certain time frame. For example, eating within an 8-10 hour window. TRF is based around the science of circadian rhythms which control hormones.
Studies have shown that people can still lose weight when they restrict the time frame in which they eat regardless of whether they restrict calories. A 2012 study found mice that ate fatty, sugary foods around the clock got sick while those that ate the same food and the same amount of calories but within an 8 hour window did not. The theory is that TRF gives the body more time to repair itself each day.
What’s coming next?
Now that you know some of the key benefits to incorporating fasting and time restricted feeding into your lifestyle, stay tuned for next week when we discuss what happens to you during a fast and how you can best work it into your current lifestyle.