As a dietitian, it’s not uncommon for me to get asked about the same diet/fad/nutrition topic over and over again. I spend a lot of time talking about the pros/cons of such things and realized that this blog might be (read: duh, Laura it’s DEFINITELY) the perfect space for me to talk openly and as candidly as possible about these topics. Intermittent Fasting is one of those topics I get asked about on the regular.
With topics such as Intermittent Fasting (IFing for short), I tend to feel like a broken record. I don’t mind repeating myself, but some days you wonder if anyone is listening. Now, as someone who views themselves as an educator and coach, it’s not uncommon for me to repeat myself weekly, if not daily or hourly. In fact, educators rely on repetition, even Aristotle believed in its power:
“It is frequent repetition that produces a natural tendency.”
That being said, let’s get on to one of the hot topics I get asked about all the time, shall we?! Know that I try my best to view a fad diet/fitness trend from all angles but want to provide you with my sassy dietitian opinion on it all. That’s why you’re here, right?! Let’s get on with the show then.
What is Intermittent Fasting?
So glad you asked. Well if we break down the two words first, here’s what we get:
Intermittent (adjective): coming and going at intervals: not continuous
Fasting (intransitive verb): to abstain from food; to eat sparingly or abstain from some foods
So from those two words, we get something along the lines of “not continuous abstaining of food” or something along those lines. While it may sound terrible to do such a thing, MOST of you abstain from food at least for a few hours in your 24 hours of being alive in a day. So I guess in some sense we all intermittently fast aka sleep. Unless you eat in your sleep or bring food into bed? You might be the exception.
Why do I bring this up? Well, it seems that Intermittent Fasting is becoming a thing…AGAIN. It’s one of those fads that seem to recycle over and over and over. Why? Because it can work for a small subset of people and so they shout it from the rooftops and then they share their success and everyone wants a piece of their six-pack pie. And so we health professionals quietly roll our eyes, take a deep breath, and educate in the hopes of creating positive health changes.
Types of Intermittent Fasting
The thing with intermittent fasting is that when people are talking about it, they may be talking about different types of fasting. Yes, there are different ways in which you can fast, shocking, I know. This, of course, makes it even more confusing if you are trying to follow guidelines. Let me break it down for you.
This is probably the most popular type of intermittent fasting. This is where you have a restricted window for eating. In this case, 16 hours of fasting and 8 hours of eating. So, for instance, you could eat between 10a-6p or 12p-8p and then fast the rest of the day. Some people also loosen that window to 14:10 or even 12:12. Heck if you are just started out a more favorable window of 8:16 would work.
The reason this works is that a shortened feeding window means that you have fewer hours to cram in the total caloric intake. Chances are you will be too full and won’t eat too much of an excess. It also works because you are only restricting the time in which you restrict intake, not the consistency of what you’re intaking. So you, in essence, could eat whatever you want within this feeding period and not feel restricted. I’m not saying I recommend it, I’m just saying you could eat whatever you want. Chances are if you eat like an idiot you won’t see results, just saying.
This is another common way people fast. You choose 2 non-consecutive days within the week (or 7 day period) where you fast for a full 24-hour period. The rest of the 5 days you can do whatever you want. This promotes a caloric-deficit over a 7 day period.
So, once again, you are restricting a feeding window in hopes to restrict the total number of calories consumed. No quality of food mentioned, just a miserable 2 days of hunger and hatred. I’m sorry I mean, a day with no food and just fasting.
While this may not be a recognized diet per se, this is the original way we used to (and still do) see fasting. If you ask anyone who partakes in a fast for a religion they are not doing it for weight loss, instead, they are doing it for a bigger reason beyond themselves. They are doing it to show respect to what they believe in and tend to also cut back on activity. However, people have become interested to see if there is any health benefit to such a thing, just google scholar it.
The results?! Varied and non-conclusive at best. In some cases, it has been shown that fat loss and some metabolic markers (namely lipids) were improved. However, because no long-term research has been done I feel like it’s not really a great model to base your health on. The other issue I see is that most won’t continue this type of fasting regimen throughout the year so it’s short-term and does not promote any positive diet or lifestyle change. Save it for the holidays, respect it, and move on.
Unintentional & Realistic Fasting
As I mentioned earlier, we all can think of a time we unintentionally fasted. For instance, maybe you overslept/slept-in and went 12+ hours without food. Maybe you had a procedure or blood test and were required to go without food for 12+ hours. Maybe you were so busy yesterday with kids, work, errands, etc. that you literally forgot to eat for 16 hours. THIS HAPPENS.
Honestly, I believe this is the only fasting we should be doing. Sure, some can benefit from time-restricted feeding but putting a fad diet label on it is absurd. The goal of eating is to nourish and feed. You are meant to feel hungry before you eat and not-hungry after you eat. You are meant to feel energetic with a stable mood throughout the day. If fasting works for you and makes you feel all the above great, if it doesn’t chances are it’s not for you. End of story.
This whole intermittent fasting thing we probably shouldn’t call a diet. Instead, we should call it a feeding regimen. A diet normally involves more of a way of eating (i.e. Keto, Paleo, Vegetarian) and less of when to eat. As research shows more and more, it’s more important to focus on how MUCH we eat in total. SO, that being said, if fasting helps you eat an amount that supports lean body mass as well as energy, mood & performance and decreases fat retention, perhaps it will be okay for you. It just depends, but don’t push your success story on someone else, unless you know for a fact it will help them.
Pros of Intermittent Fasting
There is a reason this feeding regimen has gained more steam AGAIN. It’s because there are most certainly some benefits to eating this way. The major reason this works is that, once again, the feeding window is decreased in some capacity and thus overall intake is decreased for most. You can totally eat like an idiot and overeat as well, so it really just depends. Here are some pros to IFing:
In some (not all) we will see overall weight loss and most importantly, fat loss. This is a pro if you need to lose weight, of course. This happens for many because…
Reduction in total caloric intake
This type of feeding regimen will make it more difficult to overeat. I’m not saying you CAN’T overeat I’m just saying for many it will be hard to do so. This reduction in caloric intake is what promotes weight loss. It can also help to give the digestive system a break as well as your insulin response. This may over time ensure that your blood sugar stays stable…however, the verdict is still out on that, once again, give it a google scholar.
Frankly, restricted eating windows may elevate cortisol which then elevates blood sugar, and then we’re back at square one, see below.
This may be the biggest pro to IFing. Why? Well because we’re all just grown-up children who want to eat whatever we want. For some this way of eating is easier to wrap our head around because then we can eat whatever food we want without feeling deprived. We also dont have to worry to much about prepping because we can grab whatever food is available to us during that window.
We can shorten the feeding window but we can keep our soda, candy, cookies, donuts, and beer. I’m not suggesting you do that but let’s be honest, there is a part of you that would be happy to restrict your feeding window if it meant you could eat ANYTHING you wanted.
Cons of Intermittent Fasting
Honestly, if you look at a lot of recent posts/podcasts on Intermittent Fasting, you will hear a LOT about the positive. So while I don’t want to be the bearer of bad news, I’m going to lay down the hammer. Once again, there are pros so I’m not saying there aren’t but when the diet fails you…know that there are reasons it does. Some cons I see with IFing:
Hunger & Lack of a Sustainability
You know the word “hangry”? That word comes to mind when I think about fasting. Now, I’ve fasted unintentionally and probably do so once or twice a week. However, I’m not restricting my window and suffering through hunger, that sounds miserable and frankly the complete opposite of intuitive eating. Being hungry over and over again is anything but sustainable. So, one of the biggest issues is that this diet or fad or feeding regimen will not last and will not serve you over time.
To me, a healthy diet/lifestyle is one that is sustainable and keeps you healthy for as long as possible.
Intermittent fasting, if done anything but unintentionally, just isn’t sustainable for most. Yes, for some it will become a way of life, for many others, it’s just not realistic.
Speaking of hunger. Has being hungry ever made you STRESSED?! That isn’t just emotional stress, that is also physical stress. By not eating for extended periods of time, you may elevate your hormone called cortisol. This is your fight or flight hormone. You know the one you feel when the car in front you unexpectedly slams on the brakes?! Yeah, that one.
A spike in cortisol causes your blood sugar to spike. Too much spiking of blood sugar over time leads to poor control of blood sugar (leading to pre-diabetes and more) as well as weight gain. Seems like the complete opposite effect we were going for, right?! Once again, eat when you are hungry and feed your body, end of story.
Bingeing &/or eating disorder tendencies
This is one of those topics many who promote this way of eating in the fitness world forget. Some people may have a tendency to slip into disordered eating or even eating disorder patterns and behaviors. Telling someone to a. eat only between certain hours and/or b. eat whatever you want as long as it’s within a given timeframe can do more harm than good.
Why? Well, I see two very terrible consequences for those that may have a tendency for an eating disorder.
- Bingeing: By restricting, someone may then go to binge when they are finally able to eat. They may have no control once that feeding window is open, leading to disordered eating at the very least.
- Restrictive Eating: give someone an inch they’ll take a yard. Tell someone to restrict 16 hours a day and suddenly they are restricting 20 hours a day. Tell someone to restrict 2 days a week, now they’re restricting 5. This can go downhill fast. If you know you have those tendencies, this isn’t for you.
You see the issue here?! Intentional IFing is NOT for everyone and if you are not a trained professional who knows what to look for, you may be doing more harm than good as it comes to your recommendation. The more you know.
Lack of proper fueling
The sports dietitian in me is screaming into the computer. If you are an athlete of any level, fasting especially around training is the dumbest thing I’ve ever heard. It’s especially even more problematic if you are someone trying to gain weight or at the very least gain/maintain muscle. If you are NOT fueling yourself around exercise/training, you run the risk of having to over-tap into your muscle glycogen stores and suddenly your body is breaking down muscle as opposed to gaining and building muscle.
Another issue is having the fuel to support your performance. Ever bonked?! Yeah, fasting will help you with that bonking. Let’s not bonk and instead eat to perform. Ok, great.
Lack of muscle gain
I know I just said this but I think it’s worth repeating. It is VERY hard to build muscle if you are in a caloric deficit. If you are someone looking to gain muscle, you must be incredibly diligent with your fasting if you want to see gains. Anything is possible but if you want to go the fasting route because you feel better in other ways (i.e. sleep, gut, etc.) then I highly recommend working with a professional to make sure you aren’t losing any muscle. #doitforthegains
I’ve alluded to this throughout this whole (longer than intended) post. This type of diet/fad/feeding regimen does not discuss or recommend any type of quality. If you know me, then you know I’m a quality over quantity gal. I don’t really give a crap if you have abs and eat donuts/pop-tarts/candy because I can guarantee that will all catch up with you. Focus first on quality and then we can worry about quantity, kapeesh?!
Who is Intermittent Fasting For?
Dare I say it?! It depends.
I will never stop using that answer because it applies to almost everything as it applies to health and fitness. Hopefully, the above ramble/rant will give you insight into if it is right for you or not.
Speaking from experience, I tend to find that this way of eating works better for males over females. There are different hormonal factors coming into play so it’s not a shock that a male (dominant in testosterone) adapts better to a restricted feeding regimen than a female(dominant in estrogen). That being said there are exceptions. Look at your goals, how you feel, the sustainability of this way of eating for you, and your overall health. Then you may have your answer. If not, seek a professional’s opinion, not some insta-famous-lack-of-experience-but-has-abs preacher of this way of eating.
Phew, okay Sassy OUT. Let me know what questions you have, happy to continue the conversation!
It wouldn’t be a bad idea to check out some extra information on the topic as well if you’re interested click here.
My research also suggests for some pre-menopausal women it can mess with fertility and your cycle. No good .
Laura Ligos, MBA, RD, CSSD says
would love to read more on that!
Alicia Wise says
Once again I’m in the camp of “If it works for you, great!” but its not for me. I need to be fed, watered and walked regularly.
Laura Ligos, MBA, RD, CSSD says
Yes! Same same 😀