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I was out having dinner with my wife a couple of nights ago and she asked me what my next video was on. I said it's a video explaining the difference between low carb and ketogenic diets, to which she replied, "They're the same thing, aren't they?" Which highlights the main reason that I'm making this video, because these two terms are often used interchangeably and they shouldn't be. There are some very important differences. All ketogenic diets are low carb, but not all low carb diets are ketogenic. It's kind of like all thumbs are fingers, but not all fingers are thumbs. The second reason is that while I've been researching this video, I've seen this topic explained very badly. It's no wonder people are confused. So let's do this properly.
Hi, I'm Dr. Dan Maggs. I'm so glad you've landed on my channel, which is all about achieving lasting weight loss through low carb real food nutrition. Today I'm going to be focusing on the difference between low carb and ketogenic diets. This video is not about which of those is better or what the pros and cons of each are. I'm not going to be telling you which type of diet is right for you, if either of them are, but I will be making those videos soon, so make sure you subscribe to my channel if you're not already so you don't miss those when they come out.
So, yes, both low carb diets and ketogenic diets involve restricting the amount of carbohydrates. As a starting point, let's consider what most people in the Western world eat on a daily basis. It's going to be a combination of all sorts of bread, rice, pasta, some protein, maybe not enough. And if they've been listening to what our governments have been preaching for the last 50 years, not very much fat. It varies quite a lot from person to person and from country to country, and clearly not everyone is following their government's advice to the letter. But broadly speaking, the standard Western diet is upwards of 250 grams of carbohydrate per day, per person, and often considerably more. As many of us learn at school, but most of us have forgotten, all of the starches in the bread, rice, and pasta break down into glucose once they're in the body. Glucose, which is commonly called blood sugar, can be used by cells all over the body for energy. It can also be stored as fat. Fat cells turn excess glucose into fat for storage.
Let's compare that to a low carbohydrate diet, which, as you probably can guess, aims to reduce the amount of carbohydrate consumed. If you're consuming less carbohydrate, you'll end up with less glucose in your blood, and therefore your pancreas will produce less insulin. The reason that is important is because insulin is our main fat storage hormone. It's what triggers those fat cells to take up the glucose and store it. That's why doctors, whenever we start anyone on insulin injections, always warn them that the main side effect is weight gain. Having lower insulin levels allows us to actually use our fat stores for energy rather than simply keep adding to them.
So how low is low carb? There's no universal definition of how low a low carb diet should be. Lots of scientific papers use less than 130 grams a day, but if you read around the internet, you're going to find figures quoted from anywhere between 100 and 150 grams a day. So that's around half of the amount of carbohydrates when compared to a standard diet. But what does a low carb diet look like? In practice, that means you're going to be significantly reducing your intake of bread, rice, pasta, basically all of those white or beige foods. Importantly, you're going to be significantly reducing your intake of refined sugars. You can pretty much eat all vegetables on a low carb diet, but you're going to want to manage the portion sizes when it comes to starchy vegetables like potatoes. Similarly, you're going to be limiting, but not eliminating, fruit. Because we're cutting back on carbohydrates, generally your protein and fat consumption will go up a little bit, and our bodies tend to adapt to a low carb diet quite quickly and easily, and you won't usually get any side effects when restricting carbohydrates to this kind of level.
But there is an important safety point. If you're diabetic and on medication to lower blood glucose, you should always consult your doctor before starting a low carbohydrate diet, as you run the risk of dangerously low blood glucose levels. Now, unfortunately, not all doctors are comfortable adjusting medication for low carbohydrate diets. So I've linked to a useful paper down below that you can give to your doctor that basically tells them how to do it.
Let's look at the ketogenic diet, sometimes called the keto diet. If we restrict carbohydrates more aggressively, we'll get to a point where we're no longer consuming enough glucose to meet our body's basic needs. Running out of glucose like this isn't really something that most people in the modern world have to concern themselves with. Most of us have food security and an adequate supply of carbohydrates. But running out of glucose was a frequent challenge for our hunter-gatherer ancestors. Fortunately, we evolved our way around it and we can simply switch to an alternative fuel source. When your body is running low on glucose, your liver will begin to produce a fuel called ketones, which it makes from fat. This can be the fat that we are consuming or the fat that is stored on our bodies, which, as you can imagine, is incredibly advantageous for those of us who are looking to lose excess weight. During the process of turning fat into ketones, your liver also produces some glucose, so your blood glucose won't drop completely, even if you stop eating carbohydrates altogether. Once ketone levels build up in your blood, you've entered a metabolic state called ketosis. The majority of the cells in your body will happily run on ketones as their main source of energy. For example, after three to four days of being on a ketogenic diet, 75% of the brain's energy source is from ketones.
So the key thing that defines a ketogenic diet is that it causes the body to enter the metabolic state of ketosis. In order to get into ketosis, you must be consuming a very low level of carbohydrates. So we can consider that ketogenic diets are a subcategory of low carbohydrate diets. All ketogenic diets are low carb, but not all low carb diets cause you to enter the metabolic state of ketosis. For the sake of simplicity, from this point onwards, when I talk about a low carb diet, I mean low carb diets that are not ketogenic.
Now, I need to make an important distinction here. It's important that we don't confuse ketosis with diabetic ketoacidosis, but it often is confused given the obvious similarity in the name, even by doctors. It's possible to have dangerously high levels of ketones in the blood. This is a condition known as diabetic ketoacidosis, or DKA. DKA is a serious, life-threatening complication of Type 1 diabetes and less commonly Type 2 diabetes. This is the reason I think many doctors freak out when they hear keto anything. All doctors know only too well that a patient in diabetic ketoacidosis is critically unwell, and honestly some of the sickest patients we ever treat. So doctors are understandably jumpy at the very mention of the word. The key difference is that patients in ketoacidosis not only have very high levels of ketones in their blood, way higher than we'd ever get on a ketogenic diet, but they also have very high glucose levels. When we compare this to somebody who is in ketosis due to diet, we find normal levels of glucose and moderately raised levels of ketones. Going from this to ketoacidosis isn't possible, because if we consume carbohydrates to raise our blood glucose levels, we'd stop producing ketones.
So how much do we need to restrict carbohydrates to get into ketosis? I'd love to give you an exact figure, but the truth is that it varies from person to person. It can vary based on your activity levels, your genetics, and your physical size. Clearly, someone who is six foot four is going to have different needs to someone who is five foot one, but generally speaking, we're looking at somewhere between 20 and 50 grams of carbohydrate per day. Fortunately, it's quite easy to find out if you're in ketosis. We can measure the levels of ketones directly with a simple finger prick blood test. You'll also pass some ketones out in your urine, where we can measure them with dipsticks. I've made a video all about the different methods of testing ketone levels, which I'll link to up here.
So what does a ketogenic diet actually look like? Most fruit and vegetables are restricted, and starchy vegetables, typically the ones that grow underground, like potatoes, are completely eliminated. Above-ground vegetables like cauliflower, broccoli, cabbage, and lettuces are generally fine, because they're very low in carbohydrates. Most fruits, other than berries, which are very low in carbohydrates, are also gone. You'll need to focus on consuming an adequate amount of protein for your body. Again, that will vary based on how active you are, and that's much the same as on a low carbohydrate diet. The big difference is that when you cut back on carbs so much, you need to replace those carbohydrates with fat. Importantly, and this is something that I see explained incorrectly time and time again, it's not the adding of the fat that causes the body to go into ketosis, it's the restriction of the carbohydrates. You go into ketosis if you just stop eating altogether. The increased fat consumption is to help you feel full after a meal. It's not there to trigger ketosis. So a ketogenic diet is usually described as a very low carb, moderate protein, higher fat diet.
But doesn't eating fat make you fat? There is a common misconception with the ketogenic diet that you're just spooning fat into your mouth all day, eating bacon and cheese and nothing else. Thank you, Instagram. But no, ketones actually inhibit hunger and trigger a reset on the feedback systems that tell our brains to stop eating when we're full. We don't fully know the mechanisms by which this occurs, and more research is definitely needed in this area. But people who are in ketosis therefore naturally restrict their food intake without the need for counting calories. The experience of hunger on a ketogenic diet is radically different. Most people will drop from eating three meals a day plus snacks to two meals a day, or even one meal a day, without really feeling hungry.
A ketogenic diet can cause some side effects. I mentioned earlier that a low carbohydrate diet is generally well tolerated by the body. But with a ketogenic diet, there are a set of transitional symptoms that are collectively known as keto flu. These occur when our bodies are simply not used to being in ketosis. For many of us, the only time we've ever spent in ketosis is when we've been unwell and not able to eat. It's important to note that side effects are to be expected and are not a sign that ketogenic is not right for someone. All that is happening is a drop in insulin levels as a result of carbohydrate restriction, and that means the kidneys lose some fluids and electrolytes. Thankfully, these side effects are usually able to be minimized by focusing on hydration and electrolyte replacement. There is a document which you can download free from my website that takes you through how to easily manage the side effects of ketosis. I'll leave a link to that in the description below.
So both low carb diets and ketogenic diets are low in carbohydrates, but the ketogenic diet is very low and, therefore, is higher in fat. A ketogenic diet is defined by the metabolic state of being in ketosis. There are some more transitional symptoms with a ketogenic diet, but these can be easily managed. And a ketogenic diet is by its very nature more restrictive than a standard low carb diet. But in some ways, that makes it simpler. Some people love the clarity of being able to test their ketone levels and say, "Yes, I'm in ketosis." But given that our governments have been pushing a low fat message for pretty much the last 50 years, it's natural that some people have safety concerns about the additional fat you need to consume on a ketogenic diet. I made a video earlier this year called "Is Keto Safe?" which addresses in some detail all of the safety concerns that people commonly have around the ketogenic diet. I'll link out to that at the end of this video. I'm going to be doing a follow-up to this video in the next couple of weeks, where I'm going to look at keto versus low carb: which is better? So make sure you subscribe to my channel so you don't miss that one. Have a great day.