What is Intermittent Fasting (IF)?

Intermittent Fasting: An Overview of the Benefits

If you are wanting to lose weight, maintain your weight or simply want to improve your overall health, you might want to try intermittent fasting, or IF. This approach to eating uses an intermittent schedule so that you might enjoy several research-backed health benefits. There are several different types of IF, allowing you to choose the method that fits you and your lifestyle the best.

What is intermittent fasting?

People who do IF fast intermittently during the week. It is more akin to an eating schedule than a diet. Some people combine IF with other diets such as low-carb/high-fat or low-calorie diets. Others simply eat normally during part of the week while eating on restricted calories two days per week or forgoing food for 12 to 18 hours per day while eating meals during the remaining windows of the day.^[1]

What are the health benefits of IF?

Studies have shown that there are multiple potential benefits of IF, including:

• weight loss,
• weight maintenance,
• lowered risks of cardiovascular disease and diabetes,
• improvements in blood sugar levels,
• and potential protection against neurodegenerative diseases such as Alzheimer’s disease and dementia.

A researcher at the University of Chicago, Krista Varaday, has found that IF is easiest for people to follow when they combine their fasting schedules with diets that are moderately high in fat.^[2] In her study, Varaday found that people who followed an IF schedule of alternate-day fasting lost weight regardless of whether they followed a high- or low-fat diet on their regular eating days. However, the subjects who followed the moderate high-fat diet enjoyed similar weight loss and cardiovascular protection as the subjects who followed a low-fat diet on their eating days.

Dr. Mark Mattson, a neuroscientist at Johns Hopkins Medicine, has conducted multiple studies on the benefits of IF. In one study in 2011, Mattson studied 107 obese subjects. Half of the subjects were assigned to a calorie-restricted diet on a continuous basis while the others were assigned to an IF schedule. Both groups lost weight during the six-month study period. However, the people who followed the IF schedule lost slightly more weight than the low-calorie group and helped to reduce the risk of disease.^[3]

Another study in which Mattson was involved looked at the use of IF to help to prevent neurodegenerative diseases and to prolong life. In this study, Mattson and his colleagues conducted a review of the literature and found that animal studies showed that following calorie-restricted diets or fasting intermittently both helped to protect against neurodegenerative diseases and to prolong the lives of the subject animals.^[4] In his study of the animals that were fed on an IF schedule, Mattson found that the neurons in their brains reacted better to oxidative and other stresses that can lead to the development of such diseases as Alzheimer’s and dementia.

Different kinds of IF

There are several different kinds of IF that people can follow. Here is an overview of each type to help you to determine what might work the best for you.

Alternate-day fasting

An alternate-day IF schedule involves your restricting your calories on alternate days to no more than 500. On the opposite days, you can eat without calorie restrictions. Varaday’s study, which was described above, looked at alternate-day fasting for both low-fat and high-fat diets. Both groups lost weight, but the high-fat diet group had greater compliance. She also found that the subjects did not eat significantly more than they should on their non-fasting days.

Fasting at night and in the morning

In a study that was published in 2016 in the journal Cell Metabolism, researchers found that not eating during the evening hours or the morning hours may help people to lose weight and to enjoy other health benefits.^[5] In this style of IF, you either stop eating around 5 pm at night or avoid eating when you first wake up until lunch time.

12- and 18-hour fasting

Dr. Mattson, who has conducted numerous studies into IF, has followed an IF schedule for decades. He restricts the calories that he eats each day to a six-hour window and fasts the remaining 18 hours. People who eat in a 12-hour or 18-hour fasting schedule limit eating to specific windows of time during each day. For example, if you are on an 18-hour IF schedule, you might limit your caloric intake to the hours between 12 p.m. and 6 p.m. If you are on a 12-hour IF schedule, you might limit your caloric intake to the hours between 8 a.m. and 8 p.m. each day.

How to do IF

Like other lifestyle changes, it can be difficult for people when they are first trying an IF schedule. Dr. Mattson states that starting IF for people who haven’t done it before is similar to what people who have been sedentary experience when they begin exercise programs.^[6] This means that you should expect it to be hard at first until you get used to the change. It might be a good idea for you to try to ease into it slowly. Start by trying to limit your eating after a certain hour each night if you are planning to do the 12- or 18-hour schedule, for instance, and gradually build up from there. If you plan to try alternate-day fasting, reduce the calories that you ingest on the alternate days gradually over a few weeks.

During your fasting times, it may be a good idea to make certain that you have a full schedule. This can help you to get through those hours without thinking as much about food. Remind yourself that you will not starve simply because you are fasting for a few hours. The day before your first day of fasting, eat plenty of food so that you will begin the fast without feeling hungry. Finally, if you slip up, forgive yourself and get right back on your IF schedule. Over time, IF will become easier.

IF schedules can help you to lose weight and to enjoy many other health benefits. IF may allow you to enjoy a healthier life while helping you to live longer. It might also be easier for you to adhere to as opposed to low-calorie diets that are ongoing.

You may also be interested in our articles on the Keto diet and the Paleo diet. Both of those are often combined with Intermittent Fasting eating.

Sources

1. https://well.blogs.nytimes.com/2016/03/07/intermittent-fasting-diets-are-gaining-acceptance/

2. https://www.ncbi.nlm.nih.gov/pubmed/22889512

3. https://www.ncbi.nlm.nih.gov/pubmed/20921964

4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2622429/

5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5388543/

6. https://well.blogs.nytimes.com/2016/03/07/intermittent-fasting-diets-are-gaining-acceptance/