Is Intermittent Fasting Healthy?

Intermittent fasting, or IF, is a method of eating that entails fasting for periods of time throughout the day. Rather than consuming meals at breakfast, lunch, and dinner times, IF adherents give themselves a relatively brief window during the day in which to meet their dietary needs. While this method of eating can be very helpful for some people, there are situations where it may end up doing more harm than good.

How does intermittent fasting work?

Intermittent fasting works by restricting the amount that followers can eat. The most popular protocol is 16/8 — or fasting for 16 hours, and only eating during 8. Some adherents choose to do alternate day fasting, which entails eating more on some days, and less (or nothing) on others. Still others choose to fast for 20 hours, allowing themselves only 4 for eating. Many 20/4 adherents follow an OMAD protocol, or “one meal a day.”

The short- and long-term benefits of IF.

In animal studies, subjects that followed an intermittent fasting protocol showed improvements in blood sugar, body composition, and other metabolic markers. In humans, weight loss was the primary result. That said, losing weight alone is often enough to improve health markers like blood sugar, blood lipids, and body composition. Some people respond better to intermittent fasting than other methods of calorie restriction. So, while IF may not yield more dramatic results than portion control or other methods of reducing calorie intake, it is still a very valuable tool for those who did not respond to more traditional weight loss protocols.

Some research has shown that intermittent fasting may be able to help improve glucose metabolism. This effect is generally limited to adherents whose eating window occurs early in the day. Eating meals early, rather than later, can even improve metabolism in those who don’t end up losing any weight. This may make early meals a helpful long-term strategy to fight metabolic impairments.

The downside to IF.

Fasting, as a practice, has been around for millennia. That said, research on how it actually effects the body is still very new. Most of the studies of intermittent fasting are of relatively short duration, so we don’t really know how it impacts the body when followed as a lifestyle. A study performed by a team of researchers at the University of São Paulo in Brazil found that fasting may damage the pancreas and impair the action of the sugar regulating hormone insulin, increasing the risk of type 2 diabetes. Other studies found that fasting can increase oxidative damage in the body by producing free radicals.

While intermittent fasting is a very promising way to help adherents lose weight, it is not a cure-all. As with any diet or lifestyle change, it’s important to discuss with your provider to determine if the possible benefits outweigh the risks.

Who shouldn’t try IF?

There are a number of cases where intermittent fasting is contraindicated. For people with a history of eating disorders — especially anorexia nervosa, bulimia, or binge eating — a fasting protocol can trigger a relapse into disordered behavior. Intermittent fasting may also cause increased PMS symptoms, irregular cycles, or other menstrual difficulties. People suffering from hypoglycemia, stress, or elevated levels of cortisol may find that IF makes them feel lightheaded, irritable, or anxious. Lastly, children, people who are pregnant or breastfeeding, type 1 diabetics, insulin-dependent diabetics, and people who are underweight should avoid fasting. For those for whom IF is contraindicated, healthcare practitioners generally recommend a diet consisting of small meals with a high protein content and good quality fat to help meet calorie needs and keep blood sugar stable.

Intermittent fasting is essentially a method of calorie restriction. While it isn’t for everyone, there are increasing numbers of people who swear by it as an effective method for weight loss. If you are considering trying a fasting protocol, talk to your provider to determine if intermittent fasting can benefit you and figure out how to best fit it into your lifestyle.