This week, we are excited to tell you about fasting, and the health benefits it can confer. Fasting is an exciting tool for weight loss and for health, and one of the biggest advantages it offers over dieting is its simplicity. Rather than worry about what to eat for your paleo diet, or your keto diet, what is allowed and what is not, you simply must not eat anything for a certain amount of time. During this time it is important to continue to drink water (tea and coffee are usually ok too).
Fasting is also a flexible way to lose weight and stay healthy – no matter your dietary restrictions or how often you travel, simply by modulating the time between your meals, you can gain the benefits of fasting. If you do not feel the benefits in a 16 hour fast, you can bump it to 24 hours, or even several days!
Furthermore, fasting saves you money AND time!
“A little starvation can really do more for the average sick man than can the best medicines and the best doctors.” -Mark Twain
What is fasting?
Let us begin by defining fasting and clearing up a few common myths about the practice. There are 5 stages within the process of fasting, starting the moment you finish a meal.
In stage 1 (0-4 hrs), your body relies on the energy immediately available to it via the meal you just consumed.
In stage 2 (4-16 hrs), the body turns to its glycogen stores for energy. Glycogen is glucose your body has stored previously in the liver.
In stage 3 (16-30 hrs), the body’s glycogen stores will be running low, and your body begins to break down protein for glucose in a process called gluconeogenesis. By this stage, many of the tissues in your body have entered ketosis, burning fat for energy.
In stage 4 (30 hrs-24days), gluconeogenesis has fallen off a little, and many more of the tissues in the body have entered ketosis, and glycerides (fats) have become the major fuel source of the body.
In stage 5 (24 days+), the only remaining organs getting glucose via gluconeogenesis are the brain, red blood cells, and parts of the kidney. The body has almost entirely switched over to ketones, burning stored fat to provide energy.
In the following sections, we will discuss how the above stages are used to create the most common schedules of fasting.
Before we get to that, it is important to note that fasting for long periods without preparation and physician guidance can be EXTREMELY dangerous. Most notably, refeeding syndrome, which can occur during the process of reintroducing glucose back into the body after prolonged periods of starvation, can result in death if improperly handled. Those most at risk of refeeding syndrome include the heavily malnourished (BMI < 16, fasts over 10 days), but the average person will not suffer any severe consequences if they pursue fasting under the supervision of an experienced physician.
However, fasting is not for everyone – children, pregnant or breastfeeding women, and those who are already underweight or malnourished should not fast. Patients with a history of anorexia nervosa should be cautious with fasting, as should patients on medications (which is why it is important to consult your physician before fasting).
The most popular and accessible schedule of time restricted feeding (AKA intermittent fasting) is called 16:8. This consists of fasting for 16 hours a day and having an 8-hour window in which to consume meals. It is important to set this window to end a few hours before bedtime – ideally this window falls around 10am-6pm, with a bedtime around 9 or 10pm. Using the stages listed previously as a reference, you might notice that the 16:8 schedule of fasting lasts just long enough to get the benefits of stage 2 of fasting, which can help to use up the liver’s glycogen stores.
To gain some of the benefits of stage 3, one might change this to an 18:6 schedule or a 24 hour fast (dinner to dinner). To fully reap the rewards of stage 3, one might engage in a 36 hour fast (dinner to breakfast after one day). In the 18:6 schedule, as in the 16:8, it is important to set this window to end a few hours before bedtime. The 24-hour and 36-hour fast should also be paired with a healthy dinnertime (between 5-7pm).
Schedules of time restricted feeding can mostly be engaged in without fear of refeeding syndrome, but one should still consult a physician beforehand, especially if they fall into one of the at-risk groups noted above.
Alternate Day Fasting
Slightly more intensive than TRF is the alternate day of schedule. There are two popular setups for ADF, the 2:5 and the 3:4. In the 2:5, two days out of the week are spent fasting and 5 days are spent eating normally. This effectively amounts to two 36 hour fasts per week. As one might suspect, the 3:4 consists of 3 fasting days and 4 feeding days. The 3 fasting days are usually broken up so that no two fasting days fall in a row. This way, one can benefit from 3 separate 36 hour fasts per week, burning tons (not literally) of fat every week!
Fasting Mimicking Diet
Interestingly enough, the body can actually take in a small number of calories without breaking its fasting state. FMDs (fasting mimicking diets) are slightly more complex, often requiring careful supervision or meal kits. Usually FMDs last about 5 days and come with a comprehensive list of what can and cannot be eaten. The end goal of the FMD is to gain the benefits of stage 4 of fasting without too much risk of refeeding syndrome, and also make longer fasts more accessible to the general public.
If you needed help to achieve this you might want to consult at Huntington hospital.