Alternate Day Fasting: Is It Right for You?

alternate day fasting

If you pay attention to trends, you probably know intermittent fasting is having its 15 minutes of fame. You might not know that there are many intermittent fasting types, including the 5:2 method, the Warrior Diet, and alternate-day fasting, or ADF for short.

You can tailor each intermittent fasting protocol, including ADF, to fit your needs. ADF is one method that may require a bit more personalization than the others due to its more intense nature; the fasting window is very long, which could be problematic for you depending on your medical needs and your personal goals. However, after reading this, you may find that ADF is the protocol you’ve been searching for all along!

What is Alternate Day Fasting?

When you follow ADF, you’ll fast every other day and eat as you typically would on the days between. It roughly equates to a cycle of 36 fasting hours and 12 eating hours on repeat. Visually, an alternate day fasting schedule typically looks like this:

  • Day 1:  Eat regular meals
  • Day 2:  Fast
  • Day 3:  Eat regular meals
  • Day 4:  Fast
  • Day 5: Eat regular meals (you get the picture)

As with any fasting plan, it’s okay for you to change up these rules. You may find it challenging to go an entire day without eating (hello grumbling stomach!). So, you might want to try to eat on your fasting days but limit your calories.

Alternate Day Fasting and Hunger

One of the primary obstacles of ADF is that pesky hunger problem. Your body has a complex system of mechanical and chemical signals that let you know when you need more fuel. Whenever you limit nutrition (like when fasting), these signals kick in to let you know you need to eat. 

alternated day fasting benefits

You’ll hear your stomach growl and feel pangs of hunger that let you know you’re physically empty. You may also experience fatigue, light-headedness, and shaky hands, among other chronic food restriction symptoms. Hunger and other symptoms aren’t enjoyable, and if that happens to you, you may want to stay away from ADF or modify it, so you’re not constantly hungry.

Subconsciously, your body will try to get you to eat somehow. For example, people with restrictive eating disorders often report that much of their thinking is preoccupied with food to the point that they even have food dreams! Even if you don’t have an eating disorder, there’s still the potential for food thoughts to take over your mind if you follow a restrictive protocol like ADF. 

The classic 1940’s Ancel Keys Starvation Study shows food obsession can be induced in healthy individuals by starving them. The test subjects (who didn’t have eating disorders) displayed similar symptoms to people with eating disorders; these included obsessing about food during the day and dreaming about food at night! While you probably won’t experience starvation to the level the Ancel Keys subjects did, you may find yourself thinking a bit more about food if you’re feeling hungry on your fasting days.

A study from May 2020 shows ADF can decrease your calorie intake, but you’ll probably continue to experience hunger pangs for an extended period. Older studies claim that fasting every other day can decrease hunger cues over time, but this isn’t well-supported. Research on ADF is pretty limited because subjects often drop out due to hunger or diet issues, shrinking the already-small study populations.

Alternate-Day Fasting and Other Health Outcomes

A 2017 study published in the American Medical Association Journal delivered more damning information on ADF, showing fasting every other day didn’t improve health success any better than daily calorie restriction did. In this study, health success markers included adherence to the prescribed diet, weight loss, weight maintenance, and cardioprotection! Simply put, ADF had the same health benefits as daily calorie restriction, meaning a less-restrictive form of IF will get you the same results. Additionally, you should not use ADF if you have certain health conditions or are at increased risk of developing any. Because it has a fasting window that goes well past 24 hours and lasts through the day (as opposed to overnight only), don’t use ADF if you:

  • Are underweight or anemic
  • Have an eating disorder or are at risk for developing one
  • Have type 1 or type 2 diabetes
  • Are on medications which affect blood glucose levels
  • Are female and pregnant or trying to conceive
  • Have young children who will also use ADF
  • Are an elite athlete or have intense day-time physical demands

Benefits of Fasting Every Other Day

Intermittent fasting has many health benefits, including:

  • Improved sleep patterns
  • Weight loss
  • Increased longevity
  • Potential muscle maintenance improvement, 
  • Increased insulin sensitivity, 
  • Reduced oxidative stress, 
  • Better blood pressure 
  • Better cholesterol

As such, ADF does have the potential to bring about positive changes to your health, but it may be a challenging plan to maintain.

Tips for Implementing Alternate Day Fasting

alternate day fasting meal plan

As with any lifestyle change, you must pay attention to your body. Listen to your hunger cues if you are fasting every other day, and don’t make yourself uncomfortable for the sake of losing a few pounds. Don’t let your drive for good health get in the way of enjoying life!

Make sure you’re drinking plenty of non-caloric beverages on your fasting days, especially since a good part of hydration comes from your meals. Water is the gold standard here, but it is also okay to drink coffee or tea as long as they don’t have caloric sweeteners or creamers. If you add some fat, like MCT oil, to your coffee, it’s A-Okay in terms of your fast.

If you find your stomach won’t stop grumbling at you, consider having some small meals or snacks on your fasting days. Aim to have snacks or small meals that include protein and fat; foods rich in these two macronutrients help you feel full longer and are typically more satisfying. And if you decide to eat something on your fasting days, aim to limit your calories to about 25% of what you typically eat.

Your Takeaways

Current research and personal testimonies show alternate-day fasting may not be the best choice for you. It has a high potential to leave you feeling uncomfortably hungry on your fasting days and has been scientifically shown to be no different than daily calorie restriction in terms of health benefits. Because of this, it may be best for you to avoid ADF. However, a regimen like this may work well for you if you want more structure to your fasting routine. In this case, ADF may be the key to helping you stay on track with your goals. If you are thinking about using ADF, talk with your doctor to determine if ADF is right for you.

Author's bio

Grace Engels, RD

Grace Engels, RD

Grace Engels is a Registered Dietitian Nutritionist based in the Greater NYC Area. She completed her undergraduate coursework and requirements to sit for the RDN exam (including 1400 hours of supervised practice) at Cornell University. Grace keeps busy with three main jobs: Clinical ...

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