Fasting: The New Diet On the Block
By Arpana Gupta, PhD and Riya Sood
Most start the new year with optimistic resolutions around health and wellness. My husband and I decided that we were going to get a head start and end the year on a healthy note. While everyone was gathered around tables briming with abundance, we decided to go on a five-day fasting diet, a fasting mimicking diet specifically. While this sounds crazy, we decided that we wanted to gift ourselves with a fresh start on our health and fitness journey.
You have probably heard of the mantra “You are what you eat”. Though the quality and quantity of the foods we eat are important factors, many health experts have begun to think that the timing is equally crucial. This has led to the rise of many types of fasting diets that are focused on eating during a specific time as a way to restrict the daily calorie intake and achieve weight loss.
Simply put, a fast is when you abstain from eating for a certain period of time. Different forms of fasting exist. The methods vary in the number of fast days and calorie intake.
Intermittent fasting (IF)
Social media has been abuzz lately with many people hailing the effectiveness of IF to lose weight. There are many different types of IF schedules. One method is the 5:2 approach which involves eating regularly for 5 days a week and limiting yourself to 500 to 600 calories per day for the other 2 days. You can choose any 2 days of the week as long as there is a regular eating day between the two fasting days. For example, you could choose to eat regularly on every day of the week except Monday and Friday in which you will have 500 to 600 calories per day.
Time restricted eating (TRE)
Another type of IF schedule is TRE. TRE is not necessarily a way to restrict the daily calorie intake, but in this strategy, food intake is restricted to a certain number of hours each day, without necessarily reducing the total caloric intake over a 24 hr period. For instance, if you eat your meals within 10 a.m. to 8 p.m. during the active part of the day, you achieve 14 hours of fasting until the next morning. Based on both mouse and human studies, the most effective timing is 16:8, e.g., no food intake from 8 pm to noon the next day.
Circadian rhythm fasting (CRF)
CRF goes a step further than IF by not only timing your meals but making sure those meals are in line with your body’s internal clock. But first, what is the circadian rhythm and why does it matter? The circadian rhythm is the body’s internal clock that regulates our sleep/wake cycles. Our eating schedule is a major factor that impacts the circadian rhythm. CRF narrows the eating schedule to daylight hours usually from 8am to 8pm followed by a period of fasting during the night. Studies conducted on humans have shown a positive effect of CRF on metabolic health. A study from 2019 showed that following a CRF diet for 4 days decreased average daily glucose levels and altered lipid metabolism.
Fast mimicking diet (FMD)
Exactly as the name suggests, a FMD tricks the body that it is in a state of fasting while allowing some food intake. Essentially, you follow a low-calorie diet over a period of five days. Pioneered by Dr. Valter Longo, a biogerontologist and cell biologist at the University of Southern California, this diet is an effective alternative to avoid the challenging aspects of fasting: hunger, fatigue, and the food pangs. On the first day, you consume 1100 calories followed by 725 calories per day on days 2 through 5. To achieve optimal results, it is recommended to follow this diet once per month for three months.
Solid scientific evidence supports that fasting, if done correctly, helps shed pounds, beat disease, and live longer. Studies looking at the effects of fasting on the gut microbiome notice a dramatic shift in the gut microbiota population within 12 to 16 hours after fasting. Specifically, a decrease in the level of harmful bacteria (Alistipes) and an increase in the population of beneficial bacteria (Akkermansia) was observed. Beneficial gut bacteria live in harmony with our body, promoting several health benefits ranging from improved immunity to improved metabolism and better cognitive health.
“Fasting is not a new concept.”
Giving your digestive system a break from a constant input of food is also a healthy way to restore, repair, and refresh. It helps alleviate digestive issues such as gas, diarrhea, and heartburn. Furthermore, it also increases the levels of a brain-derived neurotrophic factor (BDNF), a protein that helps stimulate the growth of new neurons and improves memory and brain functioning.
Fasting is not a new concept. It constitutes an integral part of many faiths like Hinduism, Buddhism, Islam, Judaism, and Christianity. For many, fasting is considered a powerful spiritual practice. Denial of the physical needs of the body is seen as a way to purify the body and mind and acquire divine grace.
Though fasting is gaining recognition as an effective way to lose weight, there are some considerations to keep in mind. According to Harvard Health, fasting may not supply enough nutrients in the following people (Check with your healthcare provider before trying out a fasting program to make sure that it is safe for you.):
- People who take medications for blood pressure or heart disease
- People with diabetes or blood sugar issues
Just as much as consuming food supplies our body with nutrients, abstaining from it also comes with a whole set of benefits. Maintaining a balance is what good health is all about. While the five-day fast may have been a bit extreme and honestly quite difficult to adhere to, we have now settled into a routine of TRE. Limiting intake of food to certain times of the day seems doable with hectic work schedules and yet has several health benefits. So, give it a try, there may be a fasting diet out there for you that seems doable and rewarding at the same time.