Intermittent fasting (IF) is an eating trend that has once again gained popularity after being studied for its health benefits. Some people choose to fast for religious or spiritual reasons, and in fact can feel more natural than traditional eating practices. Compelling evidence on the health benefits of intermittent fasting reveals that fasting may be a viable option to help regulate metabolism and prevent and treat a variety of health concerns.

Intermittent fasting, or periods of voluntary abstinence from food and drink, guides your focus to when you’re eating as opposed to what you’re eating. A fast can vary in length, depending on your goals.

Types of Intermittent Fasting

  • Time restrictive eating. This method aims to align eating patterns with the natural circadian rhythm. In this method (16:8), you would fast for 16 hours, and eat over the course of eight. This is often the most sustainable way to practice fasting, and is definitely the most popular option.
  • Whole-day fasting. You may have heard of this as the 5:2 diet, where you eat your regular portions and at your regular times for five days, and then fast for two full 24-hour periods each week.
  • Alternate day fasting. This is the strictest form of fasting because you only eat every other day. 24 hours of eating is followed by 24 hours of fasting.

What happens during fasting phases? 

After hours without food, your body begins to run out of sugar to use for energy to keep you going. At this point, your body will look to other sources for energy and begin burning fat. Some refer to this change from using glucose as energy to using fatty acids for energy as metabolic switching.

Intermittent fasting induces a temporary ketogenic state. This promotes weight loss, as processing ketones requires greater energy. Intermittent fasting contains elements of the ketogenic diet, benefitting from increased fat metabolism, but it may actually be more beneficial than the ketogenic diet. The typical keto diet involves high consumption of animal fats, which is associated with increased cardiovascular risk.

By prolonging the fasting period, your body switches to fat burning more quickly. When choosing the right fast for you, you want to make sure your preferred method will fit into your lifestyle and daily routine. The key to any ‘diet’ is consistency, so be sure to choose a method to which you can adhere for an extended period of time. 

Metabolic Benefits of Intermittent Fasting

During periods of fasting, several things happen in your body. For example, your body initiates cellular repair processes and alters hormone levels to release body fat. Giving your body a rest from calorie intake helps regulate metabolism in the following ways.

Reduce Insulin Resistance

Intermittent fasting has promising value for people with type 2 diabetes and pre-diabetics. Studies show that IF helps decrease glucose levels in the blood and insulin resistance. For those with diabetes, IF may even eliminate the need for insulin.

Weight Loss

Many people adapt intermittent fasting for weight loss benefits. It works not only because of lowered calorie intake, but also because of hormonal changes that take place during IF. Fasting enhances the production of human growth hormone, which facilitates fat burning and muscle gain.

Lower insulin levels and higher growth hormone levels increase the breakdown of body fat. In this way, short-term fasting actually increases metabolic rate, helping you burn even more calories. Importantly, intermittent fasting increases the loss of belly fat, which plays a role in the risk of metabolic disease.

Decrease Inflammation and Oxidative Stress

Oxidative stress contributes to premature aging and many chronic diseases. Free radical damage to cells like protein and DNA can lead to cancer and other diseases. Oxidation also causes widespread inflammation in the body, as an immune system response to the damage.

Studies show that intermittent fasting helps protect against oxidative stress on the body and decreases the immune system’s inflammatory response. Other studies show that cellular repair is improved during fasting periods, thereby further protecting the body from the effects of cellular damage.

Sleep Better

A shortened eating window helps to regulate the natural circadian rhythm. Most people who fast stop eating earlier in the evening. Late dinners cause higher glucose levels than daytime meals, increasing the risk of diabetes and disrupting sleep. Nighttime eating decreases both quality and quantity of sleep.

Quality sleep does more than just help us feel good and function more effectively during the day. Adequate sleep duration and quality is also important for the normal functioning of daily metabolic and hormonal processes and appetite regulation.

Improve Heart Health

Studies show that intermittent fasting improves numerous cardiovascular risk factors, including blood pressure, cholesterol, and triglycerides. Even after a cardiovascular event, intermittent fasting may confer cardiac protection. People who engage in IF post-heart attack have a lower risk for coronary heart disease.

The Bottom Line

Given the known benefits for metabolism and other health markers, intermittent fasting is a viable method for weight loss, managing blood glucose, and preventing metabolic disease.

As with any lifestyle change, it’s always a good idea to consult with a physician. IF may not be recommended for children under 18, women who are pregnant or nursing, or people with a history of eating disorders. Listen to your body, and remember that change does not happen overnight. It takes consistency and trial and error to figure out what is going to work best for your own body.