Unless you’ve been living under a rock, you’ve probably heard about the now vastly popular diet and eating trend (or lack thereof, to be accurate), "intermittent fasting." The name alone can scare hoards of people back to their keto-friendly and gluten-free diets that don’t require them “fasting” for hours at a time. But before you write it off altogether, intermittent fasting, or IF as it’s also known, can actually be an incredibly effective method for weight loss and isn’t nearly as intimidating as it may sound.
Before you decide to skip your next two meals and jump head-on into intermittent fasting, there’s a lot you need to know about how the diet works. The diet can actually be unhealthy if you don’t follow a strict regimen and dedicated balance of eating and fasting. If this all sounds overwhelming, just take a deep breath as we walk you through everything you need to know about intermittent fasting.
What Is Intermittent Fasting?
Intermittent fasting, according to Harvard’s T.H. Chan School of Public Health, is a diet regimen that cycles between brief periods of fasting, with either no food or significant calorie reduction and periods of unrestricted eating. For many, intermittent fasting isn’t a diet at all, but rather a pattern or schedule for eating. If you’re one of those types that doesn’t eat breakfast but instead sips on a cup of coffee and waits until 1 p.m. to have your first meal of the day, then you’ve been intermittent fasting to some degree without even realizing it!
Intermittent fasting doesn’t necessarily dictate what you eat, but rather when you eat, and its methods are derived from the kind of traditional fasting that’s been practiced for millennia. Even when fasting wasn’t used for specific social or spiritual practices, it was present in the early stages of humanity simply because accessibility to food wasn’t always promised. Our hunter-gatherer ancestors didn’t have the option to pop down to the grocery store for a snack, and as a result, they learned how to cope and operate without food for extended lengths of time.
To understand how intermittent fasting works, it’s key to understand the differences between your body's "fed" state and its "fasted" state. The fed state, as you probably guessed, is the state in which our bodies are digesting and absorbing food, but in that state, it’s difficult for the body to burn fat, as its insulin levels are much higher when you’re full.
When your body is in a fasted state, however, it’s not actively absorbing any food, insulin levels are lower, and your fat cells will release stored sugar to be used as energy, resulting in weight loss. The bigger picture of IF, then, is that when insulin levels are lower for a long enough amount of time, our bodies will begin to shed weight.
Methods of Intermittent Fasting
There are a few different ways to begin intermittent fasting. None of them focuses on exactly what you’re eating but rather set strict limitations on when you’re eating.
A quick note on what to eat during the days you aren’t fasting: While a lot of the draw towards IF is due to the loose restrictions around what you eat during your allotted stretch of time to consume food, it’s not recommended that you zip through a fast food chain on your day off to fill up. A well-balanced diet consisting of low-carb foods, lots of lean protein, veggies, fruit, legumes, and other nutrient-rich foods will provide energy to your body on the days when you’re not eating… and will help you lose weight along the way, if that is your goal!
Here are some popular approaches to intermittent fasting:
The 12:12 Method
This is a great beginner method because it already closely resembles how lots of people naturally eat. This method requires you to fast for 12 hours a day and then allows you to eat for 12 hours a day. So, for example, if you finish eating your last meal at 8 p.m., then you can eat again 12 hours later at 8 a.m.
The 16:8 Method
This method is also referred to as the “Leangains” protocol, and requires skipping breakfast and has you eating for a stretch of 8 hours at a time, for example from 12 p.m. to 8 p.m. After that, you fast for 16 hours in between, so you won’t eat again until 12 p.m. the next day.
The 20:4 Method
This method is a little bit more advanced and requires you to fast for a full 20 hours a day, and then gives you a four-hour window to eat before starting over. If you decide to eat between 3 p.m. and 7 p.m., you’ll then fast overnight and eat your first meal the following day at 3 p.m.
The 5:2 Method
This is another method to ease into and requires that you eat a limit of 500-600 calories on two non-consecutive days of the week (like a Tuesday and a Thursday), and then eat normally on the other 5 days of the week.
The Benefits of Intermittent Fasting
Aside from its effectiveness for weight loss, IF—when done right—comes with loads of other benefits for the body. One major benefit to intermittent fasting is that it has the potential to help repair and regenerate cells. When you fast, your cells initiate cellular repair processes and remove old and dysfunctional proteins within the body. As you fast, your cells experience stress, and in turn, they adapt and enhance their ability to cope with stress, and to even resist disease.
Perhaps one of the most remarkable effects of IF is the research found by Mark Mattson, the Chief of the Laboratory of Neuroscience at the National Institute on Aging. He and his team have published several papers (and Mattson did a now extremely popular Ted Talk on the subject), asserting that fasting twice a week can significantly lower the risk of developing both Parkinson’s and Alzheimer’s disease.
If that’s still not enough to wow you, intermittent fasting can also help to heighten levels of HGH, the Human Growth Hormone, which can aid in fat loss and muscle gain. And, as we mentioned earlier, IF helps to lower insulin levels. Lower insulin levels mean less sugar in your body, which sets the stage to release sugar from our fat cells, resulting in easier weight loss and helps to fight against diabetes. Finally, IF can help improve heart health through reducing the amount of “bad” cholesterol, and triglycerides in the body.
Who Should Avoid Intermittent Fasting?
Although intermittent fasting can be a really helpful tool for people interested in losing weight and gaining more energy, it can also be unsafe for certain individuals who have struggled with disordered eating, or for those whose bodies aren’t equipped to handle the alternating rounds of eating and fasting.
People with diabetes should abstain from IF or consult with their doctor before starting as manipulation of insulin levels is the main result of practicing intermittent fasting and could affect those with diabetes. Similarly, if you suffer from another disorder that requires you to intake food at certain times, IF might not be the diet for you.
Because fasting is at the core of this diet, women that are pregnant or breastfeeding shouldn’t try intermittent fasting, as you can potentially cut off much-needed nutrients to your growing little one. If you’re in an active growing stage of your life—maybe you’ve just hit a growth spurt or are starting puberty—try this diet later on. Your body is in a phase that requires lots of nutrients every day, so opt for a diet without fasting that consists of lots of lean proteins and vegetables instead.
A Pattern, Not a Diet
One of the biggest lessons to be learned from intermittent fasting is that it’s a pattern of eating, not a diet, so many that have taken to this method of eating have found that they can stick with it for a really long amount of time. For others, it is about weight loss, and consistently eating the IF way may not be something you can sustain for months and months at a time. Start slowly and ease your way in with one of the more approachable methods, and—if you like it and see results—slowly move into a more advanced method with a healthy and balanced diet for support.
Emma Trevino is a freelance writer who splits her time between Los Angeles and Wimberley, a small town situated on the Blanco River just outside of Austin. She's combined her passion for wellness and beauty with her knack for telling stories to help brands communicate their narrative in an honest way. When she's not writing, you can find her swimming in the river, growing veggies in her garden, finding tasty natural wines, and reading on her porch.