Nearly three-quarters of American adults are overweight or obese. This epidemic of caloric overload and sedentary lifestyles puts people at increased risk from all kinds of life-threatening conditions, including stroke, heart disease, diabetes and mental illnesses.
Enter intermittent fasting (IF). Less a diet than a time restriction on when a person eats, IF demands that adherents follow one of several schedules. These include alternate-day fasting (ADF), 5:2 intermittent fasting, time-restricted feeding (TRF), and a fasting-mimicking diet (FMD).
Intermittent Fasting
An eating plan (or eating schedule) that cycles between hours of fasting and hours of eating on a regular basis (usually daily).
A mounting body of research shows that the various kinds of IF do what their evangelists claim: lowering body mass index and glucose metabolism, decreasing cholesterol and even reducing some of the markers of inflammation.
This growing evidence is attracting more and more interest from people who want to lose weight and be healthier. And researchers haven’t found a significant difference between the version of IF a person chooses. What matters most is the same as any attempt to modify behavior—finding what works best for you.
“The key is to come up with an approach that is sustainable for you, that works with your personality and fits with your lifestyle,” says Stephen Anton, an IF researcher and the chief of the clinical research division at the University of Florida’s Department of Aging & Geriatric Research.
Ultimately, there are a couple of things that make IF a better choice than typical difficult-to-maintain caloric restriction protocols. First, IF makes consuming fewer calories over a week less arduous by letting people eat what they want most of the time. Also, a metabolic switch can occur whenever fasting involves taking in very few carbohydrates. It requires as few as 12 hours for the body to switch into ketosis, a state where cells burn fat for energy instead of carbohydrates. Ketosis has an appetite-suppressing effect, potentially making it easier to make it through the fasting portions of the regimen.
If you’re interested in giving IF a go, here are the different varieties and what they require to be successful:
Alternate-Day Fasting
ADF is a day-off/day-on plan. If you follow a strict ADF lifestyle, you’ll eat nothing every other day and your regular meal consumption during non-fasting days. Many people choose a less challenging version of this approach, called Alternate-Day Modified Fasting, that lets them eat up to 500 calories a day for women and 600 or less per day for men while fasting. You’d be surprised what you can squeeze into a 600-calorie day—an egg white, avocado and tomato scramble for breakfast; a turkey wrap for lunch; and a spinach, lemon and shrimp salad for dinner.
5:2 Intermittent Fasting
The 5:2 IF approach divides a week into five normal eating days and two non-consecutive fasting days, which can be complete fasting or very low-calorie days (again, 500 calories a day for women and 600 per day for men). Many followers of this lifestyle modification choose to fast on Mondays and Thursdays.
Time-Restricted Feeding
TRF divides a 24-hour day into an eating window that can last up to 12 hours, followed by a fasting window extending up to 20 hours. The most popular form of TRF is the 16/8 plan, where the person eats for eight hours and fasts for 16 hours. Some people select an early eating window from 8 AM to 4 PM, for example. Others begin later with a noon to 8 PM window.
“The 16/8 TRF approach is one of the intermittent fasting diets that seems to be a better alternative to the misery that simply restricting calories continually would impose on us,” says Juvenescence Chairman and co-founder Jim Mellon.
Fasting Mimicking Diet
FMD doesn’t involve any complete fasts but focuses on very low calorie intake over five days. It’s also a plant-based ketogenic diet packed with nutrients, offering the follower plenty of beneficial fiber and more healthy fats than conventional keto approaches.
So whether you’re looking to maintain healthy body weight, shed pounds, or just be healthier, IF may offer an easier, more sustainable route than traditional diets. Feasting—and fasting, for that matter—never looked so good.