intermittent fasting: what it is & if it's for you

originally published 5/28/2017. updated 6/1/2020.

fasting? isn't that like...starving or something that monks or super religious people do?

well, yes and no.

some people call it a "diet;" others say that it's just a natural way of life that our ancestors (AKA the hunter-gatherers) had to practice because there was no way they had a fridge full of snacks handy for whenever they felt like eating.

then there’s the fasting for women vs. men — since we women have very different bodies and hormones than men, our bodies can respond differently to fasting.

although well-known people (from Hugh Jackman to Tim Ferriss) swear by it, it’s up to you to do the research and decide if you want to try it out.

disclaimer: I am NOT a doctor or health professional. this article is based on research.

that’s what this article is here to do — empower you to make informed decisions about your health and your way of eating.

disclaimer: please proceed carefully if you have a history of disordered eating. I have struggled with an eating disorder in the past, and this can be an easy trap to fall in — justifying something as “healthy” when it’s actually disordered eating behavior.

the important thing to keep in mind with IF is that you should be eating adequate calories on days that you are eating, and if you’re doing time-restricted feeding, it should be the ~ same amount of calories as usual, just in a compressed window.

if you find yourself binging or obsessively thinking about food while fasting, stop fasting.

the most important thing is to listen to your body.

let’s get into the details of fasting.

intermittent fasting: what it is

there are a few different ways to do IF.

time-restricted feeding

this breaks down the day into eating and non-eating hours.

the most common ratios (fasting:non-fasting) are 20:4, 18:6, 16:8, and 12:12.

I personally did the 12:12 for a long time — simply because I like eating dinner early and I usually sleep for 8-9 of those 12 hours. then I’ll have breakfast (notice how it’s “break” “fast”?).

when I’m traveling or at home for extended periods of time, I’ve found that I shift toward a 14:10 or 16:8 pattern.

what that looks like is:

  • 6:30PM: finish eating dinner.

  • 10:30PM-7AM: sleep.

  • 7AM-10:30AM: drink water and black coffee. walk my dog. I’ll workout in the AM fasted ~2-3x a week. I also sip on ACV with water, lemon juice, turmeric, cayenne before breaking my fast.

  • 10:30AM: make breakfast & eat it. I like a mix of fat and protein (more low-carb) — usually, that’s eggs and avocado.

  • and repeat!

leftover salmon, 1 fried egg, broccolini, seaweed, ½ avocado, handful of macadamia nuts

leftover salmon, 1 fried egg, broccolini, seaweed, ½ avocado, handful of macadamia nuts

resource: how to break a fast for women [VIDEO] by thomas delauer

5-2 method

this is how it sounds: eat regularly for 5 days and fast for 2 days.

for the fasting days, you can also cut down your calories to 500-600 calories per day.

you can break up the fasting days however you like, whether that’s 48 hours in a row or broken up throughout the week.

alternate-day fasting (ADF)

I recently discovered this thanks to Jess of Keto Rewind ‘s video.

it’s a fascinating concept — you fast every other day. this typically ends up being ~36 hour fast, because you have 2 sleeps and 1 whole day of fasting.

some people do this for a whole month; some people have been doing this for over 100 days.

I personally don’t think I can successfully do it and be as active as I am, but if you have a lot of weight to lose (ex: Jess was classified as obese and 200lbs+ when she started), this could be a good option.

this is essentially the “feast and famine” diet that may extend life.

resource: alternate day fasting — the basics [VIDEO] by thomas delauer

one meal a day (OMAD)

this simply means fasting for however long… but only eating one meal a day. this meal can (and should) be quite large to accommodate for not consuming anything caloric during the rest of the day.

I did a 24 hour fast and was amazed at how clear my mind was and how much energy I had, but like ADF, I don’t think I can maintain this long-term (maybe a 1x a month thing).

resource: I LOVE the Zero app for fasting (no matter the length) — you can track when you start, when you finish, how many hours you have left, how you feel, etc.

the benefits

so, why the heck would you not eat? different people do it for a couple of different reasons.

1. it can improve focus and productivity

this study was done on mice — so huge disclaimer there — but it shows improved memory due to a reduction in oxidative stress in the brain, which can impair memory and increase brain aging.

other than that, it's become all the rage in Silicon Valley because people swear by the increased clarity (I agree!).

2. it legit makes life easier

meal prep? worrying about your yogurt going bad on the commute from home to work? all of the time spent prepping and worrying about food is drastically cut, allowing you to focus on things that matter more.

this is one of the reasons why intermittent fasting is popular among people who are considered "life hackers" (ex: Tim Ferriss); it's similar to successful people like Mark Zuckerberg and Barack Obama having a set uniform every day.

with less energy expended towards worrying about smaller-picture things, you have more energy to devote toward big-picture things (starting or running a company).

3. it may improve health

there are a variety of metabolic benefits, but one key health benefit is that it reduces insulin resistance (aka improves insulin sensitivity).

if you're asking yourself wtf that is and why it matters, I did too.

basically, it lowers your blood sugar levels and can help prevent type 2 diabetes.

it can also help protect your gut microbiome and lower inflammation (disclaimer — this study was done on fruit flies, but apparently they have a 61% genetic match with humans disease genes).

4. you may lose weight

ok, this one seems like a given.

but for people who are extremely obese, this can be a good way to do it.

like I said before, it's not a diet.

you don't have to eat or not eat something. you only have to eat during certain time periods, part of which you're sleeping for, which makes it easier to stick to.

in addition, it increases the oxidation of fat while sparing your muscles, making it easier for you to lose fat rather than muscle mass. essentially, while you’re fasting, your body is drawing on its fat stores.

the downsides

there are quite a few obvious downsides to this, and I think it's important to address them.

first of all, like any health study, the research is not 100% solid. most studies are done on mice or male men; in addition, all people respond differently to different things because, as we all know, every body is different.

women especially receive fewer benefits and have more risks from intermittent fasting (though these are mostly for the fasting for a couple of days rather than the time-restricted feeding window form).

if you are exercising a lot, already very lean, and have high amounts of stress, you can be at risk of becoming amenorrheic (losing your period).

I think this advice from Mark's Daily Apple sums it up beautifully:

Most of all, though, I’d simply suggest that women interested in fasting be cautious, be self-aware, and only do so if it comes naturally. It shouldn’t be a struggle (for anyone, really).

a more important topic to address is the psychological impacts of intermittent fasting.

because no matter what you call it, fasting is not eating.

and if you have a history of disordered eating or calorie restriction, this can be an unintentional way to spiral back into old habits.

in this 2016 study of "healthy" women (i.e. women who did not self-report eating disorders), some women reported feeling a sense of achievement at abstaining from eating.

for anyone who has experienced restriction, this sense of achievement is very similar to why restricting eating can be addicting.

if you ever find yourself feeling proud of yourself for not eating rather than finding that fasting sometimes allows your body to reset and takes less of a toll on your digestive system, STOP. talk to someone. think about why you feel this way, and, as always, feel free to reach out to me!

common questions

  • what breaks a fast? anything that has calories. so black coffee will not break your fast, while coffee with cream will. (tip: add cinnamon to coffee if you want some sweetness!)

  • should I exercise while fasting? you can! it typically depends on the length of the fast, though. if you’re doing time-restricted feeding, working out fasted in the AM and then breaking your fast can help you burn more fat (fat oxidation is greater when working out fasted). if you’re doing a longer fast (24 hours or more), listen to your body’s cues. I found that for a 24 hour fast, doing yoga and LISS (low-intensity steady state) cardio like walking, jogging, or swimming felt great.

  • how do I know if I’m hungry? a lot of times, we’re not actually hungry. you’ll know hunger — it’s a physical feeling, rather than a mental need to use food to satisfy emotional responses/stress/anxiety/cravings.

  • what should I break my fast with? drinking warm cinnamon water, bone broth, or ACV with water right before you break your fast can help with bloating. depending on how your body feels, you can start with a small meal or a larger one, but stick with real, whole foods rather than processed, sugary foods.

think it's for you?

ask yourself these before you start:

  • why do I want to do it? if you feel like you're 100% fine with how you feel right now, then is there really any reason to start this?

  • what do I want to gain from it? have some type of goal in mind.

parting thoughts & advice:

  • listen to your body. if you wake up and you're starving, it might just be the increased cortisol in your system in the morning. give it some time. drink some tea or coffee (and most importantly, at least 8 oz of water); if you're still hungry after 30 minutes-1 hour, eat.

  • start slow. don't just jump into 16:8 or full days of fasting right away. start slow and build up to it.

  • know your routine. IF is the easiest when you're super busy and have a lot to do. if you're just sitting at home with a fridge full of food, it's likely that you'll snack from boredom. also, if you're exercising a lot, make sure that you're eating enough.

other resources

health & fitnessNancy Chenfasting2 Comments