The Truth About Intermittent Fasting: One Size Doesn’t Fit All - Ask a Nutritionist

Transcript:

Leah: Hello and welcome to Dishing Up Nutrition's “Ask a Nutritionist” podcast, brought to you by Nutritional Weight & Wellness. My name is Leah Kleinschrodt. I'm a Registered and Licensed Dietitian and your host for the show today. So on today's show, I'm going to discuss a topic that comes up fairly frequently with my counseling clients.

It's a topic that garners a lot of attention on social media, podcast, blogs, books, you name it. And that topic is intermittent fasting. It's a big topic with a lot of rabbit holes that we could dive down. As I was going through this, the outline kept getting longer and longer, but since this is our mini episode, I'm going to do my very best to condense down some of the latest research about intermittent fasting, but also add some of my own insights from my clinical experience with working with clients around fasting.

It will probably end up still being a little bit longer of an “Ask a Nutritionist” than what we usually try to keep it to, but just bear with me. We're going to talk about what's real, what's hype, and then most importantly, kind of help you run it through your own filter and decide if this is a potential path for you to explore and how you can do it in a way that would support your health and your goals and doesn't detract from them.

I want to just remind, put a reminder out there that we do have a Facebook page called Dishing Up Nutrition. You can search for it on Facebook. This is the primary place to leave your questions and suggestions for topics that you would like us to address, either on our full length shows or on the shorter “Ask a Nutritionist” episodes.

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What is intermittent fasting?

So let's get into intermittent fasting. Let's just start with the basics. What is intermittent fasting and intermittent fasting? It's, it's not a diet in the traditional sense. You're not told what foods to eat or to avoid, although I will have some things to say about that a little bit later on. It's more focused on when you eat, and so the idea is that you cycle between periods of eating and then periods of fasting or not eating.

Now the common, I'd say the most common patterns that I see out there, include, probably the most common one I see is called the 16/8 method. This is a type of intermittent fasting. This is actually called time restricted eating, if people have ever heard that term before. And time restricted eating is just a form of intermittent fasting.

So intermittent fasting is more of the umbrella term. Time restricted eating is kind of a subcategory of that. I am just going to call everything that we talk about today intermittent fasting, just because that's kind of the common nomenclature and I think most people can kind of follow me through that piece.

So in the 16/8 method, this is where you fast for 16 consecutive hours and then you eat during an eight hour window. So the majority of people I've met who are trying this method of intermittent fasting, they typically skip breakfast and they eat their first meal of the day around noon, one o'clock, two o'clock in the afternoon, somewhere in there.

And then if you kind of march that out, eight hours, then their eating window kind of closes, should we say, between eight and 10:00 PM. So the food typically gets shifted a little later into the day. Then there's something called the five/two method. So this is where you would eat normally for five days during the week, and then you either fast or you eat very low calorie.

So like 500 calories a day on two non-consecutive days during the week. So now we're taking, we're kind of going from a day-to-day method, and now we're zooming out a little bit and looking at the whole week. So we're eating normally for five days, eating low calorie or fasting for two days out of the week.

Then there's alternate day fasting. That's where it's kind of what it sounds like. You fast every other day, or you consume very minimal calories on those fasting days, and then every other day besides that, you're eating your normal diet.

And then there is a strategy called OMAD or one meal a day. And it, that's also exactly what it sounds like. You just eat one time per day. So you can actually kind of think of it as like you're fasting probably for about 23 hours out of the day and then you're eating window is one hour out of the day. It's just a different way to think about it. So again, this is less about restriction of specific foods and more about the timing of foods.

That doesn't mean that the quality of your foods don't count, and we'll get into a little bit more of that later. But that is again, like we're just putting some different parameters around eating patterns in this way.

Why does intermittent fasting get so much attention? (& some possible benefits of it)

So why does intermittent fasting get so much attention? Let's dig a little bit into the research. So number one is weight management. And so in my experience, weight loss or weight management is the most common reason I have clients or when I talk to people like they're trying intermittent fasting. When you shorten your window of opportunity of eating in a day, you may naturally reduce your overall calorie intake.

And I say may because that's, it's not always the case. But again, when you're used to eating for 12 to 13 hours out of the day and you put it down to eight hours out of the day, likely you will probably eat less in general over the day than you would if you had that bigger window.

Beyond that, fasting can improve insulin resistance, and that's just how your body uses insulin and whether glucose gets used up for energy or stored as fat. So sometimes it's a little hard to tease apart the weight loss and the blood sugar, the insulin resistance piece, but they are definitely two separate entities.

And there are several studies that show that intermittent fasting can be just as effective as traditional, like calorie cutting diets for weight loss. Actually, the British Medical Journal, which is one of the oldest and most highly regarded medical journals out there, they just published a study a few months ago, so this was in June of this year.

It was conducted by researchers at the Harvard School of Public Health. And they analyzed 99 different clinical trials that involved more than 6,500 people. So this is a very large systematic review and network meta-analysis, and that means they took all these trials and all these data points and just tried to summarize the big picture data or look for the overriding patterns across all of these trials and all of these studies.

And what these researchers found was that intermittent fasting diets have similar benefits to caloric restriction in when we talk about weight loss and when we talk about cardiovascular health. And so essentially it just means that focusing on eating in a certain period throughout the day can show similar results to just like eating less, like many of us have been told to do in order to lose weight.

So why might that be? I mean, that kind of again, dovetails us into one of the other health benefits of intermittent fasting is that you might see better blood sugar balance. And this is a topic we talk about all the time on Dishing Up Nutrition. Fasting, when you go longer periods of fasting, it does give your body a break from constantly processing food.

It gives insulin levels a chance to come back down and stay lower for longer periods of time. This allows blood sugar levels to come down and there's more time for that glucose to get used up by our brain, by our muscles, by our liver, et cetera, before we turn around and we start eating that next meal.

So this type of eating strategy may be especially beneficial for people who struggle with some of that insulin resistance. We've seen high blood sugars on lab work, people who are at risk for prediabetes or type two diabetes. So we've got the blood sugar piece.

There can be some benefits for digestive health, and this could come in a couple of different forms. There is a system in our intestinal tract called the migrating motor complex, or MMC. This is electrical and muscular activity that gets turned up when we're not eating. So when we are in more of that fasting state, the MMC is working a little bit harder, working a little bit better, and the idea is it sweeps out undigested food, some bacteria, debris from the digestive tract.

I like in my mind, I kind of think of it like a giant broom that kind of comes through in between meals and kind of sweeps everything down the track a little bit further. It's, it is kind of like housekeeping for the gut and anybody who has kids or a family when you're trying the, we know that the best time to try to clean house is when nobody is in the house already making it a mess as soon as we clean it up.

So same idea. The MMC works best when it gets a break from food so that it can do its job. And intermittent fasting is one way to give that gut a break or some, you might even call it like a gut rest in order for the gut to be able to do some of these housekeeping processes. And this is, as opposed to having like continuous snacking, eating every 90 minutes to two hours throughout the day.

So that's digestive health. There is, in terms of heart health, some evidence that intermittent fasting can lower blood pressure, reduce cholesterol, may decrease C reactive protein, which is just one of those markers of inflammation. And so all of those things kind of get wrapped into our heart health picture.

This was also, this was all information that had come out of that big Harvard study that I mentioned earlier. So again, they were looking at intermittent fasting from a lot of different angles from the blood sugar angle, from the weight loss angle, from the heart health angle, from a lot of different, a lot of different angles.

Lastly, not necessarily lastly, but one of the other big ones that I wanted to call attention to is intermittent fasting may be helpful for brain health. With intermittent fasting, sometimes you'll hear this word autophagy thrown out there. It basically is, it's again like another process where your body is doing some housekeeping.

It is kind of gobbling up the dead cells or the dead tissue, or it's stuff that isn't useful for the body anymore and it's getting rid of it. We naturally do this autophagy, a lot of it when we're sleeping, when we're getting that deep restorative sleep, and we're doing a lot of that recycling and that housekeeping already.

But when it comes to our brain, this is a way to, again, it's kind of like doing spring cleaning for our cells, but also for the brain. So a little bit more extended fasting may protect your brain, reduce some of that oxidative stress and you know, time will tell a little bit more as the research goes deeper, but this may be helpful for lowering the risk of neurodegenerative diseases like Alzheimer's or like dementia.

So a lot of different things I think that intermittent fasting could be beneficial for. It does have some powerful benefits if it's done in the right way. As with anything, it's not the miracle cure. It's not going to be the one thing that rules them all. And I do want to make a note too, before we leave this topic of health benefits, I wanted to mention that the benefits that I just mentioned with blood sugar, with gut health, with heart health, you may actually still even see some of those benefits through intermittent fasting, even if you don't lose a significant amount of weight with intermittent fasting.

Again, most people jump into intermittent fasting as a weight loss strategy, but even with that insulin sensitization, lowering inflammation levels like there may still be some really great and powerful benefits that you might even see, even if the weight loss piece isn't there. So keep that in mind that you might see those positive changes or that there might still be benefits to be had, even if you didn't necessarily hit that one weight loss goal that you had kind of set out with.

Who would not be good candidates for intermittent fasting?

Alright, so we talked about a lot of the great benefits that could be part of intermittent fasting. I do want to talk about who would not be a good candidate for doing a trial of intermittent fasting, because fasting isn't for everybody. I would say it is not advised to start a fasting practice if you are a woman who's planning to become pregnant, if you are pregnant, if you're in those early postpartum weeks and earliest postpartum months, and if you are breastfeeding.

The idea is the nutrient demands in this stage of life with pregnancy, postpartum, breastfeeding, that kind of stuff, these nutrient demands are staggering. And this is not the time to potentially compromise nutrient and energy intake when especially, as a woman you are, you are probably mostly the one responsible for bringing this child to life and making kind of nurturing them in those early weeks, early months. So this would not be a great time to potentially do something significant to slash calories or to compromise the nutrients that you're getting at this time.

Another category of people that I would be cautious about this with is somebody who's already underweight, so already has a lower BMI or already trending a little on the underweight side.

Another category of people: if you have struggled with an eating disorder in the past, or you still kind of have this warped relationship either with food or with your body, in essence, intermittent fasting is kind of a form of restriction; not again so much in the quality of the food, but more around like putting boundaries around times that you're eating.

This type of restriction can feed into some of that disordered mindset, those disordered relationships with food and body, things around rules around food. So if anybody has either an active or history of eating disorder, this would probably not be a great option for you.

I would say children should not fast. Again, like we don't need to be restricting growing bodies, restricting nutrient intake for little humans that are in a rapid phase of growth. Someone who's undergone surgery or a trauma and we're, we need some of those extra nutrients and we need especially a lot of protein to do a significant amount of healing, I would definitely be very cautious around intermittent fasting with this category of people.

And I think people, you could argue that maybe again, like our repair processes are upregulated during that fasting state, but I think it's, in my opinion, it would be too fine of a balance between a little too much fasting where we're getting some of that repair in, but also potentially getting too nutrient depleted to do the repairs that are needed because again, healing from a surgery, a trauma, anything like that is going to require actually more protein, more nutrients than usual. And that could become difficult to meet if you're kind of constraining your food intake into this particular window.

Potentially same kind of idea of if you are an older person, say like 55 or 60 plus, we do tend to be a little bit more insulin resistant as we get older. So again, like we know intermittent fasting can be beneficial for insulin resistance. I would just be cautious. Also, as we get older, we do tend to run the risk of losing muscle quickly.

And, we don't, I wouldn't want to compromise some of that muscle loss with trying to maybe just take a couple of pounds off. I would rather have people have a good amount of muscle and we work through other strategies to shed off maybe some extra body fat or do some body recomposition versus losing some of that precious muscle.

And lastly, I would say if you are managing certain conditions like diabetes, and especially if you have medications on board that are already steering your glucose in a certain direction, or if you're already, if you have medications that are steering your blood pressure down, jumping feet first into a more strict fasting routine is probably not the safest bet.

It would be best to talk to your medical provider and meet with a dietitian like one of us at Nutritional Weight & Wellness to get the best advice of how you would want to approach this and do it more gradually and do it in conjunction with your provider so that if we need to adjust medications, we're not running too low in blood sugar, we're not running too low in blood pressure. And potentially getting into deep water there.

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All right, so I know that was a lot of information right there. I've still got a little bit more that I want to cover, and I just want to pause here too and say, alright, hopefully you've been able to take all of this information so far, run it through your own filter your own lens, and decide if this is truly something that you want to dip your toe into the water with.

How to safely start intermittent fasting (if you fall into one of the categories where it might be recommended)

And if you're at that point, like let's talk about how you might start intermittent fasting safely if you're just curious about it and you want to like give it a go. So intermittent fasting, how do you get the most benefit out of it? If you think about it, we all fast every night while we sleep.

So the hours between when your, your last food of the previous day and your first food of the current day, like that is how long you're fasting. So say if you had that after dinner snack at 8:00 PM and then breakfast is the next morning at 8:00 AM, alright. We've already got like a good 12 hour fasting window where actually hopefully you don't even necessarily feel like you're fasting at that point.

So most of us hopefully are doing a fast for about 12 hours overnight without even thinking about it. So now if you are encouraged or want to try lengthening that window out, let's talk about how we might do that. And I would also encourage people to just approach this with curiosity and as a way to through a lens of self care, as opposed to this is another way to restrict myself. I feel guilty about the way I ate last week while I was on vacation. So now I'm going to fast or, or in a desperate motion for weight loss.

Like I would just approach this from a lens of I'm going to do an experiment. I'm going to see what happens and how I feel, and I'm going to take that information and then decide if that is something that is worth it to me or that fits with my lifestyle. So number one. Choose the method that fits your lifestyle.

So again, if you're new and maybe you typically only fast overnight for nine or 10 hours, you can start with that 12 and 12 hour method. So you fast for 12 hours, but then eat during the next 12 hours during the day. So the 8:00 AM to 8:00 PM kind of schedule. And if that already feels easy, if you're already doing something like that, then look at extending it. Maybe by going an hour more every couple of days till then you're more like 14/10 or 16/8, and see how you feel.

I mean, one indicator is if you're going to bed hungry, if you're waking up in the middle of the night because your blood sugar is dipping, that might be a sign like, hey, you're not actually having enough chance to eat enough during the day to sustain you throughout that night. So you may need to either back off, or you may need to start a little bit more gradually or take it, you know, just take that process a little bit slower.

You may need a bedtime snack. You may need a little something to balance your blood sugar throughout the night. So it's best, again, just not to go too drastic in one direction or another. So if you're used to eating during a 16-hour window, you don't want to jump into an eight hour window.

Again, it's more about how sustainable this can be for you. Work up to that bigger fasting period. So think about how that fits into your life. Then think about, all right, once you've kind of set up what you want that goal ratio to be, you, then you want to think about, okay, what time works best for me to start eating and when, when do I wrap it up for the day?

And this is where intermittent fasting can get a little more complex than just eating within a certain window. I think, as I mentioned earlier, the most common way that I see people trying intermittent fasting is to skip breakfast. Maybe we just subsist on some black coffee or just water through the morning. Then consume most of your food in the afternoon or evening. And some people fall into this habit naturally.

They might just not be super hungry in the morning. Their digestive system isn't ready to handle food until a little later in the day. The mornings get chaotic. So it's one less thing to have on the proverbial plate to worry about. So all of those are valid things to think about and I would actually encourage people to think about trying this intermittent fasting pattern in reverse.

Actually eat a great protein rich, balanced breakfast like normal in the morning and stop eating earlier in the day. This does tend to align better with our circadian rhythm and our energy requirements during the day. We tend to be a little more insulin sensitive earlier in the day, and most of us are busy.

We're a little more active. We're using our brains, which means typically we need a little bit more fuel earlier in the day. The research does also support this idea of kind of front loading your food earlier in the day and avoid taking in the majority of your food later in the day, in the evening or at night when usually this is the time where we're more tired, we're more insulin resistant, and we're typically less active. So think like we're just chilling on the couch for a couple hours.

So this is a great example where I would rather have someone say, have like a 10 hour eating window and they're eating from 8:00 AM to 6:00 PM rather than 12:00 PM to 10:00 PM Even if it is the exact same food, I think just that 8:00 AM to 6:00 PM aligns better with that circadian rhythm and kind of like some of those rhythms that our organs and our bodies are already set up for.

For some people, like really pushing back that breakfast and subsisting just on caffeine is very stressful for the body. It could raise those cortisol levels and create some of that anxiety, or you might feel kind of shaky or kind of like on edge a little bit more. You might find that your moods really suffer in the morning without that food or without some nourishment.

So this would be, again, another time where you're paying attention to your body and your body is telling you in that sense that it needs to eat earlier. So again, I would much rather have someone like say, eat that balanced breakfast, than skip that breakfast just to save the calories or have that mindset of like, I can't eat earlier because I am doing this thing.

All of this to say too, this is assuming someone has a normal circadian rhythm or like a normal day job. Of course, if you work second shift, third shift or like you've got some crazy work hours, you might have to adjust some of this, but just wanted to throw that out there.

Focus on quality food during eating window & prioritize other key lifestyle factors

I would argue you still want to focus on the quality of the foods during your eating window. We mentioned before, like intermittent fasting in and of itself does not give specific eating instructions or like certain foods that you're eating or not eating. It's more about the timing of it. But from a real food company, I will say fasting is not going to be your free pass to just eat anything in your eating window.

We still would love to make sure that you're eating really nutrient dense foods that support your health. So real food animal protein, fiber-rich vegetable carbohydrates, maybe some greens or like some potatoes, some of those starchier, higher carb foods in there. And we want some of those healthy fats in there as well. So this is the same overarching goals for everyone, regardless of when you're eating and how much you're eating. We do still want that food to count.

Tagging onto this idea as well, I do want to throw in there intermittent fasting is not going to be the thing that saves you if sleep is terrible, if you're not exercising, if you've got a lot of toxic relationships, if you're not managing stress well in your life. So just think about intermittent fasting as a tool in the toolbox that ideally should be built on a solid foundation with these other health pillars in place as well.

Stay hydrated during fasting window

Staying hydrated during your fasting window would be really, really helpful for kind of making some of these adaptations. You can drink water, you can drink black coffee, unsweetened tea, so all of these things technically will not break your fasting state.

Electrolytes in your water might be helpful just for a little bit of mineral support, as long as it doesn't contain added sugars. Some people will do a broth, like a bone broth and still consider it a fast. It does have some calories in it, but really most of those calories should be protein, which doesn't affect blood sugar that much.

So really, again, like bone broth probably fine. Just depends on kind of where do you draw the line between what do you consider fasting and what do you still consider things that keep your blood sugars low?

Listen to your body

Then, listen to your body. If you are feeling lightheaded, dizzy, shaky, fatigued, you're not recovering well from your workouts. You feel like you're kind of dragging. Your sleep is taking a hit. These are all signs that you've gone in potentially too hard, too fast, or that may be for you in, intermittent fasting is not the best route for you.

Gradual is better than drastic when it comes to making any kind of nutrition changes. So just keep an eye on those sleep patterns. Keep an eye on your immune system. That's another one that I do talk with clients about. If you are undernourished, your immune system takes a big hit. So if you're finding that you're getting a cold every couple of weeks, it's taking longer to shake off an illness than it used to, it might just signal like, we've got a little too much stress on the body, too much stress on the system, not enough nutrients to kind of counterbalance some of that.

And take time to experiment. If you're interested in trying intermittent fasting, just have fun with it. It is an experiment. The idea is we want you to feel your best. We want you to feel good and be reaching those health goals and health markers. And just because someone is doing intermittent fasting one way doesn't mean that's your blueprint. Do some experimenting, some trialing, maybe some tracking or just some kind of light journaling to figure out what works best for you or kind of decide what tweaks would be appropriate.

Fasting differences among men & women

So before I round out, this does bring me to another point that I do get asked a lot about, especially because I'd say most of our clients here are women. There can definitely be a different response between men and women when it comes to fasting, and typically it comes back to the hormonal systems that we have in place.

A man generally can tolerate longer or more intense periods of fasting than a woman can. So ladies out there, if you're getting fasting advice from a husband, a trainer, a male trainer, a coworker, or something like that, just take that with a grain of salt and know that they're looking at it through a certain lens.

I don't want to go too much into depth in it with this particular show, because I know we have talked about hormone balance, calorie restriction, under-nutrition in some of our other shows, especially around perimenopause. So I encourage you to go back and take a look in some of those shows.

But without going too much into depth, women's reproductive hormones, especially like estrogen, progesterone, they're a lot more sensitive to energy availability. So again, do we have enough nutrients floating around in the body to be able to do what our bodies need to do and want to do? So if we go say a little too long with fasting or we go a little too aggressive with fasting, this might disrupt the menstrual cycle, it can affect ovulation because the body is perceiving that there is some extra stressors out there, that maybe it's not safe to release that egg or to, it might not be safe to have a pregnancy right now. So this could contribute to fertility issues. We're, as women, we're just set up to be more protective of our energy stores to support that potential pregnancy. So, our bodies are set up a little bit more attuned to the energy availability. So I would just, I would encourage women if you are looking into this, like be very cautious and careful about still making sure, again, like we're eating nutrient dense foods, we're still eating a good amount of protein and like in general still eating a decent amount of calories so that we're not adding extra stress on the body.

Recap

All right. So again, I wish I could have maybe another hour to talk through and really flush out more of those things. I know I've, I've already gone a long time on this particular show, but I do, so just to wrap things up very quickly, intermittent fasting does have some interesting potential benefits to it: weight management, blood sugar control, heart health, brain health.

The key though is to do it in a more sustainable, gradual, safe, tailored way to your own lifestyle. So just keep all of those things in mind. Hopefully some of the bullet points that we gave here will give you some kind of food for thought to think about that.

And again, I would just highly encourage you to run this through your own lens and decide if this is something that fits the bill for you. And if it's something that you can approach with a good mindset and kind of like a solid knowledge base to go off of. So I want to thank you all so much for joining me today.

If you found this episode helpful, please subscribe to Dishing Up Nutrition. Leave a review, share it with a friend who might also be curious about intermittent fasting. And if you're interested in meeting with myself or one of the other dietitians at Nutritional Weight & Wellness, you can visit us at weightandwellness.com or give us a call at (651) 699-3438. Have a great day.

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