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Intermittent Fasting and Shift Work

Not the Oxymoron You Think

Walker, Graham, MD

doi: 10.1097/01.EEM.0000553478.34856.2a

Dr. Walkeris an emergency physician at Kaiser San Francisco. He is the developer and co-creator of MDCalc (, a medical calculator for clinical scores, equations, and risk stratifications, which also has an app (, and The NNT (, a number-needed-to-treat tool to communicate benefit and harm. Follow him on Twitter @grahamwalker, and read his past columns at



Intermittent fasting must be a hot topic: I received many questions and comments about my article, specifically how it might work for shift workers like us. (“Intermittent Fasting Can Boost Your Life and Focus,” EMN 2018;40[10]:36;

It's much easier to fast when your mind is busy, and EPs typically have that in spades. But our varying schedules can also make fasting more difficult. With a little prep, however, you can make intermittent fasting a success.

Intermittent fasting is limiting calorie intake to a feeding period, and the longer the fast (and shorter the feeding period), the better the health benefits. I typically do a 16:8 fast, where I eat from noon to 8 p.m. (eight hours) and then consume no calories (but drink sparkling water and green tea) from 8 p.m. to noon the following day (16 hours). The health benefits can be objective changes (weight or fat loss, improving HgbA1C levels) and subjective changes (better mental focus, more energy). What you eat still matters. You can't just eat junk during your fast, and you should focus on healthy fats and proteins and limit simple carbohydrates. Sipping your latte or Diet Coke or nibbling on snacks throughout the day is constantly pinging your pancreas to release insulin, an anabolic hormone, and chronically high insulin levels cause insulin resistance.

So how would all of this work? Let's go through a run of shifts and how you could make intermittent fasting work for each. The first couple of weeks are rough, but hang in there!

  • Early morning shifts: You've been fasting since the night before. You may want some carbonated water, coffee, or tea to get the morning started, but you may realize that you're much more sensitive to caffeine in a fasted state, and some mornings you may not even need caffeine to get going because your body is heading into ketosis (which is likely responsible for the wakefulness and mental clarity). Pack a healthy lunch; you'll break your fast at work.
  • Late morning shifts: The closer you get to stopping your fast, the hungrier you become and the faster your hunger returns after it passes. Working helps keep the mind occupied, and sometimes you can supplement with carbonated water. You may pack a healthy snack (yogurt, almonds, hummus) to have after lunch, around 3-4 p.m. because more of this shift's hours are during your feeding period. Remember, you're not trying to limit your calories; you're trying to eat enough protein for the day along with filling, delicious, healthy fats but fitting your needs in eight hours.
  • Swing shifts: You've got the morning and lunchtime to yourself, so you may get some exercise early (yes, still fasting!) and make lunch at home. You'll be eating dinner and ending your fast on shift, so set an alarm around 6 p.m. to remind yourself to heat up your dinner (or order something) because evenings can get crazy in the ED, and you need to make it a priority to finish eating by 8 p.m.

Doable, right?

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Fasting at Night

I honestly have no good ideas for night shifts, so I turned to the internet for help. Thanks to Twitter, some intermittent fasting shift workers (three doctors, a nurse, a pharmacist, a power plant worker, and an auto worker) shared what they do. Interestingly, eating calories overnight stimulates insulin much more than eating calories during the day, so night-shift eating is really awful for you. (But honestly, does anything taste as good as reheated 4 a.m. pad Thai noodles?) Many of the people I interviewed work many or exclusively nights and have had massive health improvements (weight loss, resolved type 2 diabetes) doing intermittent fasting.

My interview panel does it all differently:

  • Just don't do intermittent fasting on night shifts. It's a hassle if you only work a few nights a month, and it's not worth the unnecessary added stress in your life.
  • Maintain the same fasting window every single day regardless of day shift, night shift, or being off. It's easy to be regular, but I get extra hungry at 4 a.m. having worked all night, and I feel like I should reward myself with food. It might also be hard to sleep fully fasted, but others said this isn't a problem for them.
  • Eat early in the night shift, then fast until you wake up the next day. You may give yourself until 10 p.m. to eat, work the rest of your shift, go home, sleep, and then wake up and eat lunch.
  • If you work mostly nights, push your feeding window later into the night. If you're a nocturnist, eat from 3 p.m. to 1 a.m. every day instead of earlier because you have a different sleep-wake schedule as well.

Nights are the hardest nut to crack, especially if you have a constantly changing shift schedule. I think the only way I can do a 16-hour fast regularly is if I'm asleep for at least half of the hours of my fast! I recently finished two night shifts fasted, and going to sleep fasted gave me the best post-night shift sleep I've had in years. I couldn't believe it!

It's critically important that we as a specialty try to understand and optimize our health. Shift work, particularly overnights, is really, really bad for you, and along with all the other stressors of our jobs, it's critical that we find ways to negate some of the harmful physiological effects. I can't prove it just yet, but I'm hopeful that fasting is one way.

Thank you to everyone who responded with their solutions to night-shift fasting!

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