The intermittent fasting craze has thrown dieters all over the world into a frenzy. It’s so common for many years now that many versions have come up. Is it effective? Is it even safe? If so, then which type of intermittent fasting is recommended for you try? 

To make it simpler, intermittent fasting is having a schedule of when one is allowed to eat called the feeding window and when one is supposed to fast or the fasting window. But is it really that simple?

First, we must define what is true intermittent fasting. According to the director of the Longevity Institute at the University of Southern California – Leonard Davis School of Gerontology and international bestselling author of The Longevity Diet Dr. Valter Longo, “It’s not fasting if you’re going without food for 24 hours or less. The correct term is time-restricted feeding.” Therefore, what most of intermittent fasters are doing is technically time-restricted feeding. Most fast between 12 to 21 hours a day. 

How safe and effective is time-restricted feeding and what should be the duration? Dr. Longo recommends a feeding window of 12 hours per day for optimal health. Feeding for only four to six hours a day increases the risk of gallstone formation due to diminished gallbladder motility and changes in bile composition. Bile is a greenish-yellow fluid produced by the liver and stored in the gallbladder. It is essential for the breakdown of fat and the elimination of wastes such as excess cholesterol and bile salts. Recent studies also have shown that prolonged periods of fasting may increase the risk of cardiovascular diseases. 

It isn’t just the duration of fasting that we need to consider when doing time-restricted feeding. The timing of meals must also be aligned with our circadian rhythm or natural body clock. The body produces hormones throughout the day to help maintain bodily functions. Some hormones are supposed to be higher in concentration specifically during daytime and nighttime. Our food intake and meal timing can alter the production and functions of these hormones which can be detrimental to overall health.

If you don’t eat the whole day and just have one large meal at night, you may lose weight from the decreased total caloric intake but it messes up with your overall health. Our bodies were not programmed to eat late at night. We naturally produce more cholesterol at night starting at around 7:00 pm. You wouldn’t want to burden your organs by adding more fat, carbs, and protein. Furthermore, the body should start to produce the sleep hormone melatonin at around nine in the evening. That reduces the production of the hormone insulin which is needed to control blood glucose or sugar. When we fast at night while sleeping, the liver, pancreas, gall bladder, and other organs repair and detoxify. 

Unfortunately, if we eat late at night, we don’t just increase the probability of getting non-alcoholic fatty liver disease. Obesity, diabetes, heart disease, and even cancer are also associated with late night eating.

According to a scientific statement issued by the American Heart Association, “More intentional approach to eating that focuses on the timing and frequency of meals and snacks could be the basis of a healthier lifestyle and improved risk factor management. An intentional approach to eating requires eating at planned intervals to distribute total energy intake throughout the day.”

Should you decide to try time-restricted feeding, it is best to do it for 12 to around 16 hours maximum with feeding times no later than 9:00 pm. I usually recommend no food intake between 7:00 pm to 6:00 am and as late as 9:00 am. Meals can be two to three times a day during the feeding window. 

Make sure that you do not have any medical condition that contraindicates prolonged fasting as in the case of individuals taking insulin injections and those with gastrointestinal issues like hyperacidity. It is best to consult a registered nutritionist dietitian for proper assessment and guidance. 

You will find consulting a dietitian beneficial especially in planning your food intake during the feeding cycle. After all, it isn’t just the duration and timing of meals that need to be considered. What you put into your body is more important. 

You may reap the benefits of fasting for 12 hours but if you eat unhealthy food choices during the feeding hours then that cancels out the benefits of fasting. When we fast, we break down energy stores from fat. We also repair damaged cells. When talking about cellular repair, the only nutrients that can help repair cells without causing side effects like inflammatory responses such in the case of animal based products, are found in plant sources. These nutrients are called phytonutrients or plant chemicals and antioxidants. Fiber is also exclusively found in plant food sources.

Therefore, during the feeding window, your intake must be mostly from wholesome, minimally processed vegetables, legumes, fruits, whole grains and some nuts and seeds. Fish, dairy, and other animal-based or meat products should not be a staple even if you choose to still consume them. 

When it comes to time-restricted feeding, remember that it should be aligned with the body’s natural circadian rhythm, it must not be prolonged unless you need to do 24 to 48 hours of intermittent fasting for autophagy and stem cell regeneration (this must be done with proper guidance of a dietitian), and the quality of food that you consume is very important. It’s not just about what time you eat but also how and what you eat.

[email protected]