The ketogenic diet. What is it, what’s it useful for and is it dangerous?

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Simon Long

Simon Long

Simon is a highly experienced personal trainer and behavioural psychology expert
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The ketogenic diet is a diet that is low in carbohydrates. Yes that means that the atkins and south beach diets could be classed as ketogenic. It is often cited as being beneficial for reducing fat stores. This is a hotly debated topic though. Some people say that it is very effective. Others claim that it is completely useless. Personally, I fall on the side that it can be useful, but not for the reasons that many people cite.

Before we get into that though, let’s touch on what the ketogenic diet actually is. As previously mentioned it is a diet that has a low number of calories being consumed from carbohydrates. Typically less than 20%. Now this could be achieved in 2 different ways. Either you eat a much larger number of your calories from protein or fat. Or you maintain the same percentage of calories consumed from carbohydrates, but you reduce your calorie intake to the level that the body is not taking in a severely depleted number of calories.

The second option is not advised. Reducing your calorie intake severely will not be safe, it will not be sustainable and it is very likely that you will put any weight you do manage to lose straight back on. Use the first option, eating a higher amount of protein and fat, and create a small calorie deficiency.

So now you have started a ketogenic diet and are beginning to lose fat. But why? Well to understand that you need to understand a bit more about how the body uses the different macronutrients (protein, carbs and fat) to create energy for the body.

The body breaks down carbohydrates in the gut into glucose. Glucose is what is known as a monosaccharide, or a simple sugar. It is the simplest of the carbohydrate molecules. Once broken down glucose enters the blood stream, where it can be taken up by muscles and used in an ATP (Adenosine Triphosphate) reaction, which produces the energy for the muscle to contract, which in turn creates movement.

However when carbohydrates are low there will be a low availability of glucose in the blood. Now initially the body will source its glucose from somewhere else, your glycogen stores. What is glycogen? It is how the body stores extra glucose that it cannot use at the time. The glucose will be pulled into the muscles where it goes through a process called glycogenesis. The body will use a process called UTP (Uridine Triphosphate) to achieve glycogenesis and store each gram of glucose, as glycogen, in the muscle along with three grams of water.

When blood sugar, or glucose in the blood stream, is low your body will then convert this glycogen back into glucose using a process called glycogenolysis. This will then release the glycogen and the water it is stored with back into the body, where the glycogen will be converted back into glucose and transported to the muscles for energy.

It is worth noting that this reduction in glycogen stores, and the water it is stored with, is the reason people on a reduced calories diet often lose a couple of kilos of weight in the first week. An individual stores between 6g and 15g of glycogen per kilogram of body weight. For a 70kg individual this would mean they could be storing between 420g and 1050g of glycogen. When you add the 3g of water per 1g of glycogen then the weight of your glycogen stores increases to between 1.68kgs and 4.2kgs. So although the scales seem a lot lower, your fat stores may not have changed.

There are 4 calories of energy per 1g of pure glycogen, i.e. the water it is stored with does not produce glucose, and so doesn’t produce energy. This means the 70kg individual above will have between 1680 and 4200 calories stored in their muscles as glycogen. If they are eating a reduced calorie diet then the extra calories have to come from somewhere. Due to carbohydrate being so good at producing energy the body will initially get the extra energy from its glycogen stores.

However these stores will not last long. Considering the average human needs 2000-2500 calories a day, a reduction of just 20% will result in their glycogen stores being emptied within, at the absolute most, 8 days. It is far more likely that they will be emptied within 3 to 4 days.

At this stage the body has to look elsewhere to create its calorie deficit. This is where your fat stores begin to play a big part. They hold massive amounts of energy in them. The average women has 20% of her body weight as stored fat in the adipose tissue. So if they weigh 70kgs then that means around 14kgs of their weight is fat. As fat has 9 calories per gram, this equals a massive 126,000 calories!!

As your glycogen stores are now empty, and you are not eating enough calories to pay for all of the bodies requirements, your body will begin to use a process called lipolysis to cleave off fatty acids from your fat stores. These fatty acids can then be transported around the body by the lipoprotein albumin to the muscles. Once in the muscle they will be used to produce energy.

It is worth noting that carbohydrates are the bodies preferred energy source. By a long way. They oxidise (convert into energy) twice as fast as fat, and create 6% more energy per reaction. This is the reason that carbs are the exclusive energy source for anaerobic (very high intensity) exercise. Fat simply cannot produce energy fast enough. For this reason the intensity that you can reach during exercise when you are in a glucose, or carbohydrate, depleted state will be reduced. The speed that your body can cut off fatty acids, transport them to your muscles and convert them into energy will determine how hard you can train. It is also the reason that you may feel like you have less energy in day to day life. This will improve though as your body becomes more efficient at lipolysis.

Carbohydrates are also the almost exclusive energy source for the brain and central nervous system (CNS). This means when carbs are not available the brain and CNS have far less energy to function. This is why people who are not taking in enough carbs often complain of feeling tired and unfocused. However this will only last around 8 days, at which stage your body will begin to use ketone bodies to fuel the brain. But more on them later.

So, you’ve reduced your carb intake, which has emptied your glycogen stores and begun lipolysis to break down your fat stores. Is that why the ketogenic diet is so good? Well no. All of that can be achieved with any diet that is reduced calorie. You could eat a 20% reduced calorie diet with 80% of your calories coming from carbs and still go through this process.

So what advantage does the ketogenic diet have? Well, it’s just a lot easier to stick too. You see satiety, which is how long different macronutrients keep you feeling full for, runs in the following order: protein, fat, carbs.

Therefore if you are eating a low carbohydrate, and high protein and fat, diet then you will feel fuller for longer. This means you will get less hunger pans and so will be less likely to eat more. If you suffered hunger pans and gave into them then this will reduce or even negate your calorie deficit. This in turn will slow, stop or even reverse your fat loss.

There are a couple of other beneficial factors, such as the fact that your body will become more efficient at lipolysis (breaking down fat stores for energy), which in turn will allow you to train at a higher intensity when you are not using carbs to produce energy. But mainly the satiety is the advantage. However this is not to be sniffed at. Motivation and plan adherence are the bread and butter of any health and fitness goal. Anything that makes this easier is a blessing.

But what about the bad side of ketogenic diets? Are there any disadvantages?

Well unfortunately yes. You see carbohydrate break down produces waste products that are actually used as a primer for fat oxidisation (converting fat into energy). If these primers are not available then fatty acids will not be broken down completely, producing ketone bodies. These ketones are acidic, and over time can lead to a condition known as acidosis, or in this case specifically ketosis. This results in the bodies tissues becoming more acidic than usual.

A second disadvantage is that when carbohydrates are low, although the body will prioritise using fat as energy, protein will also be used to produce energy. This is done in the liver using a process called gluconeogenesis. Because lean tissue, such as muscle, requires a constant supply of amino acids (protein) to maintain itself this reduction in amino acid availability can over time result in muscle wastage. This can be reduced however with a focused muscular training program.

Due to these two reasons it is not advised that you use a ketogenic diet for longer than 6 months at a time.

So there you have it. Everything you ever wanted to know, as well as some stuff that you probably didn’t, about the ketogenic diet. I hope it’s been useful.

As always if you have any questions give me a shout. If you have any comments them stick them in below. I always read them.

If you would like to take the next step in improving your health and fitness then come and see me for your no obligation consultation and assessment.

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Best wishes,

Si   =]