Trendy or troublesome? The facts on intermittent fasting

Intermittent fasting typically involves an eating pattern that alternates periods of fasting with periods of eating. During fasting periods you usually consume no food, but can drink water, black coffee, tea and sometimes broth. Intermittent fasting has little to do with the food you eat and more to do with the timing of your eating.

Intermittent fasting schedule

There are all sorts of ways to do it. One of the most popular intermittent fasting patterns is the 5:2 plan in which you fast for two, usually nonconsecutive, days per week and eat whatever you want the other five days. 

Another version is the 16:8 plan. The goal with this intermittent fasting plan is to lengthen the time you fast each day, building up to 16 hours, then limit your eating time to an eight hours a day. For example, if you started to eat at 8 a.m., you’d eat nothing after 4 p.m.

Most plans recommend that you follow healthy eating guidelines during the times you do eat.

Benefits of intermittent fasting

Some of the common claimed benefits of intermittent fasting include

• preventing disease
• reducing inflammation
• preserving muscle
• improving memory
• promoting weight loss

The fasting reduces insulin levels which in turn will release fat stores for energy. Fasting puts our cells under mild stress. It is thought that this stress is actually good because, over time, you can build up a resistance to it and potentially resist disease. Moreover, when going from fasting to eating, it is thought that the body is able to use the nutrition to be able to regenerate healthy cells.

What the research on intermittent fasting tell us

While this eating pattern needs more study, the early research seems very promising as far as losing weight, but it may not be any more effective than simply cutting back on the calories you consume every day.

There is also a growing body of research that suggests that the timing of the fast is very important. Matching your sleep/wake cycle by eating earlier and stopping eating earlier in the day can be effective for both weight loss and lowering glucose and insulin levels. A large review of studies published in 2017 supported the hypothesis that intermittent fasting can improve your metabolic profiles and reduce your risk of obesity and obesity-related conditions, such as liver disease, diabetes and cancer.

Disadvantages of intermittent fasting

While more study is needed, when combined with a healthy diet and for people who can tolerate it, intermittent fasting may be a promising approach to weight loss and improving your metabolic health. There does not appear to be any harm in it, either physically or mentally, but it can be hard for some people to follow. If you have advanced diabetes, are on insulin, have an eating disorder or are pregnant or breastfeeding, it is important that you check with your provider before doing any type of fasting.

If you plan to start intermittent fasting, pick a pattern that fits your lifestyle, and when you do eat keep it healthy.

Annual Review of Nutrition, 2017, 37:371-393.