Learn the definition of intermittent fasting and how to unlock its power.
It is commonly said that losing weight is simply a matter of calories in versus calories out. Eat less than you usually do, and you’ll lose weight. Exercise more than usual, you might see the same effect. But what if changing when you eat, not what or how much, would do the trick?
What Is Intermittent Fasting?
Intermittent fasting is restricting all of your eating to a specific period of time in the day. Most people eat throughout the day, starting with breakfast and ending with dinner. A person practicing intermittent fasting condenses all their eating into a shorter window of time. Intermittent fasting is a diet only in the sense that it involves making conscious choices about your food intake. It is not limiting what foods you eat or how much you eat. Some intermittent fasters eat multiple full meals during their eating window, while others might graze throughout that time.
Let’s get right to the point: intermittent fasting is an effective practice for improving mental and physical health in a variety of ways (de Cabo & Mattson, 2019). Here are some of the backed-by-science benefits of intermittent fasting:
Burning fat for fuel. Once your body stops getting glucose to burn, it uses fat as fuel instead (de Cabo & Mattson, 2019). This is the primary way that intermittent fasting leads to weight loss.
Cellular repair. While fasting, your body engages a process called autophagy, in which it recycles dead or unused cells that otherwise clutter the body and cause problems (de Cabo & Mattson, 2019).
Decreased inflammation. Certain key biomarkers of inflammation go down among fasting individuals (Wang et al., 2020).
May reduce depression. Individuals in treatment for depression saw slightly larger improvements in their symptoms when they fasted (Fernandez-Rodriguez et al., 2022).
Improves insulin resistance. Individuals with diabetes can lower their blood sugar levels through intermittent fasting. After extended fasting, some people have no longer qualified as diabetic (Welton et al., 2020).
Intermittent Fasting Schedules
Intermittent Fasting 16/8
Perhaps the easiest place to begin with intermittent fasting is to go 16 hours without eating. For example, a common pattern of fasting is from about 7:30pm to 11:30am each day. Therefore, the eating window starts at 11:30am and ends at 7:30pm. For most people, this can feel like “skipping breakfast”, although the goal is still to eat as many calories as they usually would during the eating hours.
Intermittent Fasting 20/4
The longer you fast, the more your body experiences the benefits of fasting, such as ketosis and autophagy. That means many people attempt to limit their eating window to four hours a day, spending 20 hours in fasting. A common way to do 20/4 intermittent fasting is to break one’s fast in the mid-afternoon, then finish eating in the early evening.
Intermittent Fasting OMAD
For the truly strong-willed, there is OMAD, or “One Meal a Day”. This is just what it sounds like – trying to cram all your caloric intake for the day into a single meal, or a short period of about an hour.
OMAD fasting is effective in the short-term for weight loss, but not very sustainable in the long-term. It’s hard to get a full day’s calories into your body in just an hour! Although many people practice 16/8 fasting or 20/4 fasting daily or almost daily, OMAD fasting should be undertaken only temporarily.
Intermittent fasting is a simple, straightforward technique for accessing a variety of health benefits. While it is difficult at first to sit through one’s hunger, many people have experienced the rewards on the other side.
That said, if you are considering trying intermittent fasting, try not to go into it with any particular set of expectations. The benefits to your health, your focus, or your waistline may not be easy to discern at first. Like so many techniques for promoting health, intermittent fasting needs time and commitment to show its effects.
de Cabo, R., & Mattson, M. P. (2019). Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine, 381, 2541-2551.
Fernandez-Rodriguez, R., Martinez-Vizcaino, V., Mesas, A. E., Notario-Pacheco, B., Medrano, M., & Heilbronn, L. K. (2022). Does intermittent fasting impact mental disorders? A systematic review with meta-analysis. Critical Reviews in Food Science and Nutrition, advance online publication.
Wang, X., Yang, Q., Liao, Q., Li, M., Zhang, P., … , & Abshirini, M. (2020). Effects of intermittent fasting diets on plasma concentrations of inflammatory biomarkers: a systematic review and meta-analysis of randomized controlled trials. Nutrition, 79-80, 110974.
Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (2020). Intermittent fasting and weight loss: systematic review. Canadian Family Physician, 66, 117-125.