Fasting for longevity, weight loss, and metabolic health
I’ve been fasting periodically for 19 years. I’ve done water fasts for several days at a time and week-long juice and vegetable fasts. This spring my oldest began fasting to boost his immune health so I decided to join him for weekly 36 hour fasts. Fasting is arguably one of the most powerful things you can do for your health. It has recently gained popularity in diet culture advocating for intermittent fasting (IF), which is currently an area that is exploding in research. However, fasting has been around since about the beginning of time.
Hippocrates, c. 400 BC, considered the father of modern medicine, prescribed the practice of fasting for health. He was a pioneer to say “To eat when you are sick, is to feed your illness”’. Others at the time, Plutarch, Plato and Aristotle also propagated fasting for health. To this day, all over the world, people fast for health, religious and spiritual purposes.
Why do I fast? I am very interested in, in fact fascinated by, the concept of anti-aging. Aging is what happens to the body on a cellular level in response to stress in the environment. This stress is due to sunlight, emotional and physical stress, poor diet, sugar, alcohol, toxins and other factors. Autophagy is the body’s way of handling aging by cleaning out damaged cells. Autophagy occurs while sleeping or fasting - it does not occur in a fed state. While we can’t be exactly sure out of a laboratory, we think that autophagy is initiated in humans after 18-20 hours of fasting, with maximum benefit occurring once 48-72 hours has passed. After this time, there is an increase in autophagy and a boost in stem cell production. This is important because it prevents damaged cells from becoming cancer cells. Therefore, it greatly reduces the chance of cancer occurring. Also, stem cells help with preventing organ decline as we age. This means enormous regenerative power to combat the effects of aging. We also get mitochondrial biogenesis, an increase in NAD which is involved in many pathways, and many other biochemical changes. In a nutshell, fasting activates repair processes in DNA, damaged cells, mitochondria and proteins. It also improves blood sugar and lipids and insulin and leptin sensitivity.
There are no rules around the length of time you can fast. You can fast once a week, or once a month. Intermittent fasting involves fasting for shorter periods of time on a regular basis. Intermittent fasting typically ranges from eating within a five to 10 hour window which means fasting the rest of the day. Longer fasts are typically 24 to 36 hours done one to three times per week. More prolonged fasting may range from one week to one month.
During a 24 hour fast you would fast from breakfast, lunch or dinner on one day to that same meal on the following day. During a 36 hour fast, you fast from dinner on the first day until breakfast two days later. Longer fasting periods produce lower insulin levels, greater weight loss and greater blood sugar reduction in diabetics. For diabetics, 24 or 36 hour fasts will occur two to three times per week, under medical supervision. Longer fasting periods also result in greater cellular benefit where more autophagy occurs.
What can you have on a fast? Filtered water and sparkling water, plain or with citrus slices or cucumber added to water is permissible. No artificial sweeteners, sugars, or even stevia or erythritol is allowed because these can impact insulin. All teas are great during a fast, except for those with added sweeteners and flavorings. Green tea may help suppress appetite which can be helpful. Spices such as Ceylon cinnamon can also help with appetite suppression. Black coffee is also permitted in many cases. However, coffee, tea and anything other than water can theoretically impact blood sugar if you want to be a purist.
It can take some time for the body to adapt to fasting. Typically, hunger doesn’t persist and worsen. It actually comes in waves initially, and over time it diminishes. For longer fasts, hunger will actually disappear. As the body becomes accustomed to fasting, it starts to burn its fat stores and your hunger will be suppressed. Staying hydrated helps with appetite suppression, and having sparkling water can help with a gurgling stomach. The antioxidants and caffeine in green tea and coffee help stimulate weight loss and metabolism. Ceylon cinnamon has been shown to lower blood sugars and slow gastric emptying, helping to suppress hunger.
It took a few weeks for my body to adapt to fasting. A large part of the hurdle is mental. Our inclination is to panic if we know we won’t be getting food for several hours. However, just a simple reminder that it’s not forever and it’s beneficial for your health can abate anxiety. I find that staying busy (but not too busy!) is helpful in keeping my mind off of wanting to eat. Typically, once you get past 24 hours it does get easier.
Finally, it is advisable that you consult your doctor before undertaking a fasting regimen. It is a good idea to get some blood work if it has been awhile. Diabetics and those with blood sugar dysregulation can benefit from fasting but will need extra caution. It may also be necessary to monitor various factors if you are taking certain medications. Once you do get the clear, enjoy your fasting journey to longevity!
