Intermittent Fasting vs. Keto Diet – Which One is Right for YOU?

Intermittent Fasting vs. Keto Diet – Which One is Right for YOU?

Here at Nightlight Chiropractic in downtown Orlando, we get a bunch of questions from our clients about diets. So, let’s talk about diets! A lot of patients who come in want to know what we recommend for a diet. They’re not just trying to be healthy, sometimes they’re just trying to lose weight, sometimes it’s a combination of they’re trying to be healthy and losing weight, and so we’re trying to give the best advice that we can, based on the research, so that our patients are doing the right diets for them. Two of the most popular diets that we see coming through right now are the keto diet and the intermittent fasting diet, and they’re coming from all different kinds of sources. We’d like to quickly cover the differences and similarities between the two, but also why we recommend one versus the other.

We know that people get pretty passionate about this stuff. You may read a book, a news release, or a research study that says, “this is the way it has to be,” and it doesn’t have to be that way. It’s okay if you disagree with the research that I’m quoting, with the path that I’m taking, with the determinations that I’ve made based on the research that I’ve looked at, but it’s not a one-shot deal. It’s not a one size fits all here. So if you do it your way and it works for you, keep doing it your way. If it’s going well, just keep doing what you’re doing.


Let’s go over the keto diet first. The keto diet is basically a means of decreasing your carbohydrates, so let’s call it the no-carb diet because the idea is to get your carbohydrates way down, so your body goes into something called ketosis. And ketosis is when your body starts to burn fat, your fat, the fat that’s on you, for fuel, and then uses that in place of the sugar that it’s not getting from the easily-accessible carbohydrates that it turns into sugar. And so when your body goes into that ketogenic state, and it’s burning this fat, a whole bunch of things happens to you metabolically.

One of the things that happen to you is that you get rapid weight loss very fast, and part of the reason that you get that quick weight loss so fast is that your body is burning off a lot of water. You end up losing a lot of water weight upfront, and that’s a good thing. It’s not necessarily a bad thing that you’re burning off a lot of extra water that your body is holding on to, so rapid weight loss happens within the first few weeks.

This keto diet helps with insulin resistance in type 2 diabetics, and that’s really important. When you’re overeating sugar, you end up with this insulin resistance where your body doesn’t even recognize sugar anymore. It doesn’t pack it away into cells, so you end up with your blood sugars getting out of control. You end up with this type 2 diabetes and all the bad side effects that go along with that.  The keto diet actually does a great job of helping your insulin remember: this is what sugar looks like, take it and put it inside the cell, keep the blood sugar low, and it does a great job doing that.

One of the other things that it does is it lowers blood pressure. You’re decreasing all of this water in your system, so you end up with lower blood pressure, and that’s a great side effect. A diet that decreases your blood pressure and decreases your insulin resistance? This sounds fantastic; this sounds like exactly what we’re looking for. The last thing is it does great with epilepsy. So if you have a child with epilepsy, if you’re an adolescent or even an adult with epilepsy, there’s a lot of promising research that says that it will help with your epilepsy. So getting on a keto diet can help with epilepsy.


If it sounds so good and it has all these good side effects, why wouldn’t we recommend it? There are some downsides of the keto diet. One is kidney stones. In place of the carbohydrates that you’re not eating, you end up eating a lot more fat and a lot more protein, and a high protein diet ends up causing kidney stones. It’s just what happens. It’s just one of the risks, one of the pitfalls, of changing the macronutrients inside your diet. So kidney stones are a real risk.

Nutritional deficiencies, vitamin deficiencies, mineral deficiencies are another common side effect that happens with this keto diet. And again, it happens because in avoiding carbohydrates, you’re avoiding a lot of fruits and vegetables. Fruits and vegetables are jam-packed with a lot of vitamins, nutrients, a lot of minerals, and if you’re not getting them in your diet, then you have to supplement with them. So as you’re giving up carbohydrates, you’re also maybe giving up some of these other nutrients, which is actually a really bad thing.

One of the other things that happen with this keto diet is reduced athletic performance. Now, if you’re trying to get healthy, if you’re trying to get fit, if you’re trying not just to lose weight, but also to get in shape, you don’t really want to have decreased athletic performance, right? The keto diet results in decreased endurance performance and also decreased peak strength performance. You don’t want to have negative anything when you’re trying to get fit, so decreased athletic performance is a bad side effect of ketosis.

The last thing, and the most important reason why we don’t recommend this to most of our patients, is it’s not sustainable. It’s very hard to get into ketosis, relatively speaking. You have to stop eating carbohydrates or decrease your carbohydrates so much that your body will do it. It takes a period of a few days, you end up feeling terrible as your body’s making that flip from using glucose to using fats to support yourselves, and it just makes you feel terrible. They call it the keto flu sometimes because of all the ill effects that happen while you’re going through that process. And it’s not fun to do.

Let’s say you’ve been to ketosis for four weeks or six weeks, and then you go out with your friends one night, and you drink a few glasses of wine, or you end up having a terrible night, and you eat a bag of potato chips or whatever it is, you’re going to fall out of ketosis. Then it’s going to take you a day or two to get back into that ketosis. So it’s really difficult to sustain, and it’s really difficult because small misses can end up having deleterious effects on that ketosis.


Now let’s talk about why I recommend intermittent fasting. Intermittent fasting is any eating pattern that cycles between fasting and eating, and fasting means that you’re not consuming anything dietarily. So the easiest way to do it, the easiest way to think about intermittent fasting, is if you could cram all of your eating into eight hours, that would mean that 16 hours a day you’re not eating and that’s considered that fasting period. And 8 hours a day you are eating, whether it’s one meal or two meals or ten meals, you’re getting all of your calories in that shorter time period.

And what that ends up doing is during the time that you’re fasting, the 16 hours, your body is finding different ways to go about feeding itself or maintaining itself, and it will give you similar effects to that ketosis diet, although not quite the same way. That’s the easiest way to think about it. The way most people do it is to cram all of your meals into eight hours. There are other ways to do it. You could do a 5-2, which is to eat normally five days a week, and on two non-consecutive days, you cut your calories way down to like 500 or 600 calories. You then go back to eating regularly the next day. What that does is similar to that same 16-8 idea of cramming all your meals into an eight hour period.

There’s also the eat-stop-eat method, which basically is one or two days per week, you’re not eating anything, there’s nothing but water all day and you’re decreasing your calories on that day to zero, which means that you’re going to lose weight and your body’s going to find other ways to burn fat on those days. There’s even something called spontaneous meals skipping, where you just skip a meal once in a while, and this also has good positive health effects.

I hear this all the time from patients: “Oh wait, I can’t skip breakfast. Breakfast is the most important meal of the day.” And that’s totally not true. I mean, I think that started with John Kellogg back in the 1800s, but it’s totally not the most important meal of the day. Don’t let anyone fool you. It’s one of the easier ways to get into this intermittent fasting.

So why would intermittent fasting be for you? Well, one of the first effects that you look up in the research is that it increases your human growth hormone tremendously. Now, this human growth hormone creates a whole cascade of other great benefits in your body that’s helping cells to perform better; it’s assisting tissue repair; it’s helping muscle growth. It’s like the opposite of the decreased athletic performance that you get in the ketogenic diet or the keto diet because your body is actually working hard so that it can pack on more muscle and it’s working hard so that any exercise that you’re doing, you’re getting better gains for it.

Number two, you get better insulin sensitivity. So just like with the keto diet, your body is learning again, when it doesn’t have fuel available, how do we work, how do we make fuel, and so when you’re on this intermittent fasting diet, what you’re getting is that insulin resistance departure again. So, you’re doing good things for type two diabetes. You get cellular repair, and gene expression changes towards longevity. I’ve been doing a little bit more research into longevity recently, and I love this idea because what you’re doing when you’re fasting or when you’re going from periods of fasting to eating is you’re tricking your body into thinking we have a chance now to change what we’re doing, and then when we get more food, we can go back to what we were doing before.

Your body is going through two different paths. You’re going through a period of trying to repair all the cellular damage that you’re doing, keep your DNA running so that you can keep yourselves replicating, and you’re also trying to move forward and grow and. A good balance between the two genetically and on a cellular level is happening when you’re in that intermittent fasting state. You’re getting the best of both worlds when you’re doing that.

The last thing, and the main reason that I recommend intermittent fasting versus the keto diet, is because it’s very, very sustainable. You can do this almost by accident. If you just didn’t have food in your pantry that morning, you are still getting that intermittent fasting effect. Not that I recommend doing it by accident, but you could, and so it’s incredibly sustainable. If the keto diet is all about what you eat and eliminating carbohydrates, the intermittent fasting diet is all about when you eat and just making sure that it all fits within that time.


I want to give a couple of quick answers to a lot of questions that we’re getting about intermittent fasting. This is a diet we recommend, and we typically just steer people out the door with intermittent fasting. Go find the resources that you like, that you can understand, that you’re going to stick to. When you’re in the fasting state, remember that you can drink water, tea, and black coffee. All three of those things are good for reducing hunger, so it’s recommended that you drink them when you’re in that fasting state.

You can eat whatever you want, but it’s better to be healthy. During that eight hour period, we still recommend lean meats, a lot of vegetables and foods, limited dairy, maybe a little bit of grains, but a diet based on lean meats and vegetables is going to be best for you in the long run. So during that eight hour period, if you can stick to that, you’re going to be better off for it.

The last thing that I get is some patients come back, and they’re like, “Well, how do I start? Where do I start? What do I do?” And the answer is: just jump right in. Out of those methods that I just mentioned and just talked about, you can jump right in with whichever one of those sounds the best to you. So if you typically skip breakfast anyways, try and fit it into that. Skip breakfast, just do lunch and dinner, and get into that eight hours and then don’t eat anything in the other 16 hours, and you’re good.

If you have hard travel days or days where you’re at work the whole day, you could do it one of the other ways where you’re skipping all the meals in one day or some of the meals in one day. There are some exceptions to some of this. Nursing mothers, pregnant mothers, or young children can’t be skipping meals like this; they should follow a more traditional eating pattern. But for almost everybody else, even adolescents, it works very well.


The same way that there’s a dirty keto diet, there is also a dirty intermittent fasting diet. So if I didn’t eat for 16 hours a day, and during that eight hour period I had 15 bowls of ice cream, well, first of all, I’m really not going to lose weight, but second of all, I’m really not going to be healthy. You can do both of these diets the right way or the wrong way. They’ll both give you good results if you do it in the right way, they will both give you bad results if you do them the wrong way. So be careful of what you’re doing when you’re doing either one of these diets. If you’re looking to lose weight and try intermittent fasting, just jump right in, get to doing it. I look forward to hearing how it works for you!


About Dr. Merrill

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Dr. Andrew Merrill is a passionate active clinician and owner of Nightlight Chiropractic Orlando where him and his team treat hundreds of patients each month. With a strong background in exercise science from Stetson University, clinical skills from Palmer College of Chiropractic, and continued postdoctoral training in spinal disc injuries and clinical nutrition, Dr. Merrill is very well versed in the healthcare landscape. With topics ranging from "what to do for common ailments" to "why the medical system is failing you" Dr. Merrill and this blog in particular aim to keep readers up to date on what the research shows and how you can put it into practice NOW to keep yourself healthy for a lifetime.