The Keto Diet & Intermittent Fasting: Do They Work?

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Many people are trying diets like the keto diet or intermittent fasting to lose weight. These diets aim to put your body in a state of ketosis – when your body’s preferred fuel source changes from carbohydrates to fat. Ketosis, the thinking goes, melts away the body fat.

But do diets that focus on ketosis work? UH registered dietitian Meghann Featherstun, MS, RD, CSSD, LD, tells us about these diets – and whether science backs up the weight-loss hype.

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Podcast Transcript

Pete Kenworthy

Hi, I'm Pete Kenworthy.

Macie Jepson

And I’m Macie Jepson. And this is Healthy@UH. Today we are breaking down two diets that are on the minds of just about everybody these days who want to lose a few pounds. And let's just face it. That is about everybody that I know. I guess you could call these fads. We're talking about the keto diet and intermittent fasting.

Pete Kenworthy

So, some don't even call them diets. Some I'm calling lifestyles, right? So, one thing's for certain though. There's a lot of buzz and frankly some confusion around both of these. So, I'll start with intermittent fasting cause this is one that I've tried. I'm actually currently trying now. It's, it's dieting that restricts the amount of time that you're allowed to eat. So, the appeal here is you don't need to count calories or eat certain foods.

Macie Jepson

All right, I'll jump in with keto. I've tried that before. That's an extreme low-carb diet that forces your body to burn fat for energy instead of using carbs to do that. It causes you to go into a state of ketosis.

Pete Kenworthy

Right. So, what's interesting here is intermittent fasting is supposed to do the same thing. At least that's what I thought. But are they healthy and are they right for everyone?

Macie Jepson

Well, my question is can I cheat my way to ketosis? That's what I wanted to know at the end of the day. Like can I take a supplement and make this happen?

Pete Kenworthy

Yeah. And as we know, every time we talk about any subject here is that you and I aren't necessarily the experts here, but we have one with us. And our guest is Meghann Featherstun, and she has all the answers for us. A clinical dietician at UH and a wellness coach. First, Meghann, thanks for being with us.

Meghann Featherstun

Thanks for having me.

Pete Kenworthy

What is ketosis and how do these diets get you there?

Meghann Featherstun

That's a great question. And I think in order to truly understand ketosis, we need to take a look at our body's preferred fuel source. So, that is carbohydrates. So, our brain actually prefers to run off of carbohydrates. It will burn through a quarter pound of sugar a day. It uses a lot of energy. So, if we are purposely restricting carbohydrates so we no longer have those in our diet, we know that we survive, right? We're all still around if we don't need carbohydrates. So, our body has to have another way to run, another fuel source. And what that is is fat. We all have plenty of stores of fat in our body. Even the leanest people will have, you know, 30,000 calories of fat to burn through. So, we are actually able to mobilize those fat stores, turn it into something called ketones, and that can actually pass that blood brain barrier to fuel our brain when we don't have sugar or carbohydrates around to fuel our brain. So, the premise of ketosis is when we have changed our body's preferred fuel source from carbohydrates to fat, and we break our fat down into those ketones. And that is what is now fueling our brain and our muscles and our body instead.

Pete Kenworthy

And if your body is eating fat, you're losing weight, right?

Meghann Featherstun

If you're staying in ketosis.

Macie Jepson

But is ketosis a good place for your body to be in all the time? And do both of these diets get us there?

Meghann Featherstun

So, no. Both of these diets are not going to get us there because typically with intermittent fasting, the longest period that you're fasting for is 24 hours. And it takes at least 48 hours to get our body into ketosis, to burn through those extra sugar stores that we store in our liver and our muscles and all different places.

Pete Kenworthy

So, to clarify, and just to explain intermittent fasting, if you're not familiar with it, there's a couple of different ways to do this, right? The most common one that I know of is you eat for eight hours a day, which is any eight hours, pick noon to 8 p.m., and then you can't eat again for 16 hours. So, then whenever you're finished eating your fast again for 16 hours, and then you eat again for eight. There's other ways to do intermittent fasting, right? There's the five two version of it, which is essentially fast for 24 hours, twice over a seven-day period. Essentially you're fasting for a period of time, then you're eating for a period of time. And you're saying ketosis doesn't happen because none of those…

Macie Jepson

So, what's the point?

Pete Kenworthy

What’s that?

Macie Jepson

What's the point then of this particular diet?

Meghann Featherstun

When we look at typical diets that Americans follow, it's typically what we call calorie-controlled diets. So, if you think about it, it's like a dimmer switch. It's like we're turning down the dial, we're turning down the lights, we're turning down the energy that our body is, is eating. With intermittent fasting, it's very black and white. It's an on or an off switch, right? So, we're either eating or we're not. We live in a 24 /7 food culture in the United States. There is not a time that we can't go grab something to eat, right? So, all of us are just eating for too many hours over the day. So, intermittent fasting is monopolizing on that. It's telling us that you can only eat for eight hours or you can only eat for 10 or whatever you're subscribing to. So, you're just kind of turning off that switch of I'm not consuming food. So, by default, most people are consuming less food.

Macie Jepson

OK. So, before we move to keto, I think it's important to know whether there's any science behind this intermittent fasting.

Meghann Featherstun

There is. It's been, it's been around for years. They actually kind of stumbled on this research in the 1940s, 1950s in old men in nursing homes. And they were finding that they were living for a very long time and what was going on. And a lot of them were what we are now calling intermittent fasting, right? They weren't eating very many hours throughout the day. So, it was kind of a secondary outcome of this research they were doing on these people. So, we were like, oh, we can live longer if we do this intermittent fasting, you know, other studies are showing improved insulin sensitivity. The most important for most people, right, is weight loss studies. So, they did one very large weight loss study where they put head to head a calorie controlled diet versus intermittent fasting, and they both lost similar amounts of weight. So, I think what that comes back to is that, you know, everybody has a different style, a different approach that works for them when it comes to weight loss, and this is just yet another approach that is working for some people.

Macie Jepson

So, when it comes to keto, I think everybody thinks about Atkins in the days of gluttony and bacon and eggs all day long. How is keto different?

Meghann Featherstun

You know, there's a lot of confusion about that. A lot of people put keto and Atkins in the same bucket, and they're actually very, very different. So, the Atkins diet is a very high protein diet, and the keto diet is a very high fat diet.

So, when we look at the typical distribution of what the quote/unquote recommended diet is for Americans, it's only about 30% fat. Keto is 80 percent fat. So, it's 80 percent fat, 75 percent to 80 percent fat, 15 percent protein, and then 5 percent to 10 percent carbs. So, it's completely different than the way most Americans are eating.

Macie Jepson

That can't be good for you. Huh?

Meghann Featherstun

That's questionable. Right? So, the, you know, compliance is the biggest issue with this diet. Can someone stay on a ketogenic diet and consume 80 percent of their calories from fat on a day to day basis to stay in ketosis, right? So, a lot of the research that they are doing, they control this. They give you food that meets these parameters. And they're finding from some of this research some very interesting concepts. But can we replicate that in the real world consistently enough to see these same things?

Pete Kenworthy

Is there anything…I've heard of this keto brain…I don't know, I’m not necessarily sure what it is. I haven't tried this, this keto diet. It sounds almost impossible to do. I can't imagine eating 75 to 80 percent fat. And maybe I just don't understand what, what foods have those fats? So, I guess, a two-pronged question, right? What are the foods that have enough fat that I could sustain that kind of diet and still be healthy while losing weight? And then second, side effects.

Meghann Featherstun

So, we'll, we'll do the, we'll tackle the fats first. The typical American diet, the fats that we're eating are unhealthy. They're saturated fats. They are in high fat meats, they're in processed foods, fried foods. Those are not good for us. Those are bad for our overall heart health. They drive up our total cholesterol. They drive down our good cholesterol, which is not good, right? So, if we're telling someone just eat more fat, you know, a fear of a dietician such as myself is that people are going to be consuming way too many unhealthy fats on this diet. But there are a lot of healthy fats out there like avocados, olive oil, nuts, seeds, all of those types of things are great, but those actually have some carbohydrates in them as well. So, in order to meet such a low carbohydrate, this gets really tricky to do in a healthy way. So, you know, that was the first part of your question.

And then the second part is side effects. So, going back to that preferred fuel source of our body. As we switched from preferring carbohydrates to preferring fat, I am told that there's something called, like you said, keto brain, keto flu, that the side effects when our body is adjusting to these changes in fuel source can be fatigue, fuzziness, right? A difficult concentrating, intolerance to exercise. So, our, our, our muscles want to run off of carbohydrates, so when they're not there, we can't work out very hard when we only have ketones and fat around. And they actually did a really interesting study where they looked at people's desire to exercise. And it found that when people were in ketosis, they did not have that drive to exercise, which we know that drive to exercise is an issue for a lot of Americans, right? So, then put the keto, you know, diet on top of there, and I'm not sure we're going to be exercising much.

Macie Jepson

This can't be too good for athletes, I wouldn't think.

Meghann Featherstun

It's, it's not preferred for athletes. You know, they've done a lot of interesting research looking at performance when, when someone is on a ketogenic diet. And, you know, people who are trying to backpack across, you know, a very cold climate by themselves, and they can only take so much food with them and they need to use their fat stores. There's really cool research on that, right, is to being able to mobilize their own fat stores. But what we know for competitive athletes that want to outrun somebody at the end of a race, right? That sprint capacity, that high intensity exercise will not be possible when you're on the ketogenic diet because that is a carb dependent type of exercise. So, we see performance kind of tank.

Macie Jepson

One more question. It’s the most important. Can't I take a supplement just to send me right into ketosis? Please say yes.

Meghann Featherstun

I'd be out of a job. Right? No, and that's what's, what's really hard about this is we live in a, in a world and that we want quick results fast for minimal effort. You know, that seems to be what everybody's looking for when it comes to diet and exercise. And it just doesn't exist. It's, it's hard work. It's eating well. It's exercising, and finding what works best for you and, and your goals in, in life.

Pete Kenworthy

So, the bottom line is, as it always is, eat right and exercise. But if you're going to try a diet, and you want to get into ketosis, the keto diet is the one for you. Intermittent fasting won't get you there, but it might be the diet for you as well.

Macie Jepson

Until next time, for more health news, advice from our medical experts and Healthy@UH podcasts, go to UHHospitals.org/blog.