These days, intermittent fasting—eating lightly, or not at all, for planned periods during the day or week—is something of a fitness phenomenon. The original IF bible, The Fast Diet by Dr. Michael Mosley, was an international bestseller, and dozens of other guides and cookbooks have followed in its wake. Adherents claim that it improves hormonal profile, body composition, and heart health, and celebs like Hugh Jackman, Nicole Kidman, Joe Rogan, and Terry Crews all reportedly practice it. But should you try it?
Early animal studies suggested that fasting might lead to not just better body composition, but to improved cardiovascular health, metabolic health, and increased lifespan as well. In humans, however, large-scale studies failed to show a significant difference in any health markers, including fat loss, between IF and a more conventional approach to dieting. “Intermittent fasting,” concludes one 2015 study, “represents a valid—albeit apparently not superior—option to continuous energy restriction for weight loss.”
So long as you’re consistently eating fewer calories than you’re expending, the researchers concluded, you’ll lose weight and get healthier whether you eat one huge meal a day or six little ones. The science, as the saying goes, is compliance.
While this may come as a disappointment to some devoted IF practitioners, it’s good news for the rest of us.
“Having many paths to the same goal—fat loss—means you can choose which one works best for your taste, lifestyle, and goals,” says Angelo Poli, SPN, CFT, SET, founder of the MetPro diet system. “It also allows you to switch strategies if you get bored, or if the one you’re using stops working.”
It’s important to remember that if your goal is gaining muscle mass, intermittent fasting—and, indeed, any form of caloric restriction—is not the best approach because for that, you need to consume more calories than you expend. But if you’re looking to lose fat and would rather skip a few meals altogether than watch your calories like a hawk every time you sit down to a meal, IF might be just what you need.
Feel like giving IF a try? Here are some of the most popular strategies:
<p class='slide-count'>1 of 3</p><img width="1109" height="614" src="/uploadfile/2024/1217/20241217083712213.jpg"><p class="photo-credit">RossHelen / Shutterstock</p>Alternate-Day Fasting
Eat normally on alternate days, and restrict intake to 500 calories per day—the equivalent of a light meal—the rest of the time. On fasting days, you’re allowed unlimited amounts of calorie-free beverages: water, tea, coffee.
Pros: Easy to understand, lots of research supporting its benefits
Cons: Although it’s marketed as fun and easy, you’re eating almost nothing up to four days a week. That flat-out sucks, no matter how much cheesecake you eat those other three days.
Resources: The Every Other Day Diet by Dr. Krista Varady, The Alternate-Day Diet, by James B. Johnson, MD.
Fans: Not as many as the other two, but fitness writer Jenny Sugar reported great results on the ADF method.
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The 5:2 Protocol
Perform a modified fast (500-600 calories) for two nonconsecutive days each week. The other days, eat normally, but not excessively.
Pros: Flexibility. Do you want freedom to eat normally all weekend, or to cut loose on a mid-week Girls’ or Boys’ Night Out? Done and done.
Cons: To work optimally, you still have to watch what you eat on non-fasting days.
Resources: The Fast Diet by Dr. Michael Mosley, The 5:2 Diet Book by Kate Harrison.
Fans: Benedict Cumberbatch, Jennier Lopez, Jimmy Kimmel
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Time-Restricted Feeding (TRF), including the 16:8 fast
Every day consists of a feeding window and a fasting window. You might eat from noon to 8:00 pm (or 9:00 am to 4:00 pm, or some other window) and fast the rest of the day.
Pros: Great for inveterate breakfast- or dinner-skippers, who don’t have to modify much to fall in line with its rules.
Cons: As in a standard diet, you have to stay vigilant every day.
Resources: The 8-Hour Diet by David Zinczenko, Intermittent Fasting 16-8 Lifestyle Guide by Josh Smith
Fans: Chris Hemsworth, Justin Theroux