When Dina asked me to write a guest blog post for her on the ketogenic diet, I told her straight up that although I knew that ketogenic diets were basically about utilising fat instead of glucose for energy production, my knowledge beyond this point was quite arbitrary. Indeed, after scrolling through the blog site of Peter Attia, a medical doctor who is a proponent of utilising ketosis for endurance exercise, I was only too aware of his opinion on people with WordPress accounts who, according to him, “feel entitled to spew their opinions about ketosis without even the slightest clue of what they are talking about”. As someone who is keen to learn the facts of a matter and form opinions based on evidence rather than anecdote and hyperbole, I actually share Peter’s stance and, as such, I decided to approach this post from the angle of presenting what I understand about ketosis on a very basic level, whilst also providing information and debate material that I have gleaned from various articles, via both the blogosphere and academic journals, on the subject of ketogenic diets and being in a state of ketosis.

So what is ketosis? I think that Dina has already laid this out in previous blog entries in more detail than I am going to go into here, but speaking generally, my understanding of ketosis is when lipolysis (fat release) and beta oxidation (fat burning) are up-regulated due to carbohydrate (or more accurately, glucose restriction), and the body starts to produce ketone bodies in the liver that are subsequently utilised to generate Adenosine triphosphate (ATP), which is the energy currency of our cells. When the level of ketone bodies in the bloodstream breaches a certain threshold, a person is said to have entered a state of ketosis. In essence, ketones therefore act as an alternative source of energy to glucose when it is not available, with their production considered to be an evolutionary adaptation by the body to ensure survival when faced with starvation.

Now in order to expand my understanding of ketosis beyond this basic level, I consulted Lyle McDonald’s Body Recomposition website, which is a tremendous source of objective and scientific information. My initial inquiry surrounded what is required to induce ketosis, and I discovered that an intake of carbs below 100g/day is required to induce ketosis to any measurable degree, with deeper ketotic states achievable with further incremental carbohydrate reductions. Interestingly, I also learnt that Ketostix, which are used to measure excess ketones in the urine, do not provide an accurate picture of an individual’s state of ketosis – they can, in fact, be very misleading. This is because out of the three types of ketone bodies produced by the liver (acetate, acetoacetate, and beta-hydroxybutyrate), Ketostix only measure acetoacetate. The most accurate means for testing for the presence of ketone bodies is via blood serum, and there are devices which allow a person to do this. However, I understand this to be quite a bit more expensive than testing via urine, and many people will also not relish the thought of having to regularly prick their finger by choice for a blood draw. Furthermore, the issue of Ketostix providing misleading information seems to relate predominantly to measuring ketones once fully fat-adapted, and is less of a problem in the initial stages of ketosis.

So with this basic understanding of what ketosis is and how it is induced, my next line of questioning was concerned with who would want to do a ketogenic diet and why? Now I was previously aware that ketogenic diets have been used successfully as a treatment for epilepsy, and I knew that research was also ongoing into the potential for ketogenic diets to offer a treatment option for Parkinson’s disease, Alzheimer’s disease, Polycystic ovary syndrome (PCOS), diabetes (both type 1 & type 2), and a range of neurological conditions. Additionally, Dr. Dominic D’Agostino is well-known within the nutrition sphere for his research into the utility of ketogenic diets in cancer treatment, and if you are interested in listening to his TED Talk on this subject, you can do so here. However, my main interest in ketogenic diets related to its use as a weight management tool, and also in its effects on athletic performance. Basically, can a ketogenic diet assist people in losing weight and ameliorate the ability to athletically perform in a glucose/glycogen-depleted state?

To answer the first part of this question, I headed over to Sigma Nutrition and read Danny Lennon’s excellent article on the claim that if you eat more fat you will burn more fat. Now in order to tackle this claim, Danny asks to think about what happened when lipolysis is occurring. Stored fat (in the form of triglycerides) is broken down into free fatty acids, liberated from adipose (fat) cells, and enter the bloodstream. However, this is only one stage of fatty acid degradation. In order to be utilised by the body, fatty acids must then be activated (enzymatically) and transported into the mitochondria where they then undergo beta-oxidation – at this stage, two important things must be considered. Firstly, the amino acid carnitine is required for transporting long-chain fatty acids across the mitochondrial membrane in order for them to be burned for fuel. Not only does a lack of carnitine have a rate-limiting effect on the mitochondria’s ability to generate energy, a reduction of fatty acid transport has been shown to result in a build-up of fat in which can lead to insulin resistance – this effect has been recorded in Type-2 diabetes. Furthermore, and to flag the second important consideration, even if the fatty acid cascade is functioning optimally, this still does not mean that all the free fatty acids in the bloodstream are going to be burned. Now read the following carefully, because if I followed Danny’s interpretation correctly, the following statement is important to grasp: free fatty acids will only be burned if you need to produce energy at that present moment in time. If you do not require the production of energy at that particular point, the free fatty acids will be re-esterified and stored back into adipose tissue (fat cells) as triglycerides. As such, you can have lipolysis occurring and plenty of free fatty acids in circulation, but if your energy demands are not sufficient enough for beta-oxidation to be required, then you will simply restore the fatty acids in your fat cells. Subsequently, we find ourselves back at a situation in which it would appear impossible to lose body fat without creating a negative energy balance.

In terms of offering a “metabolic advantage” when it comes to weight loss and body composition, it therefore appears that such an advantage does not exist. Evidence to support this conclusion can be found in this study which concluded that “the use of ketogenic diets for weight loss is not warranted”; this study which showed no differences in extent of body composition changes between a very low-carb (VLC) diet and moderate-carb diet; and also in a meta-analysis of 23 randomly controlled trials (RCTs) which concluded that when low-carb and low-fat diets were compared, “reductions in body weight, waist circumference and other metabolic risk factors were not significantly different between the two diets”. It has been observed that low-carb diets can generate more total weight loss than low-fat diets, but the reason I have put total in italics is to highlight the point that this issue is confounded by water loss. As insulin causes the kidneys to reabsorb water, a drop in insulin facilitated by an absence of significant amounts of carbohydrates (combined with the dehydrating effect of ketone bodies) can cause significant water loss ranging between 1-15 pounds depending on an individual’s body size. Quite clearly this poses problems for comparing total weight loss in low-carb and low-fat diets. However, in once again consulting an article from the Body Recomposition website, it is wise to consider that ketogenic diets may confer other “advantages” unrelated to fat loss that are still important. For example, if you are someone who cannot have just one cookie without eating the whole pack, and you also find yourself periodically bingeing on carbs, then severe carb restriction may be warranted in order to break the cycle of binge-starve-binge-starve. If individuals also have a significant level of insulin resistance, reducing carbohydrates to ketogenic levels may again be warranted. Then there is also the issue of how a particular diet makes a person feel.

Not everyone functions well in ketosis. Some people are said to develop brain fog, become lethargic, and generally do not feel great at all. Even after a period of weeks on a ketogenic diet, they never seem able to adapt completely, and a diet that makes someone feel rotten is clearly not one that anyone would wish to adhere to for an extended period of time, particularly if they are active and train regularly. As a general rule, if you feel good on a higher-carb diet, do not suffer from energy highs and crashes when eating carbs, and can take part in high-glycolytic exercise without any problem, then the chances are that a ketogenic diet will make you feel terrible. These people most probably have excellent insulin sensitivity, are fairly lean, active, and also have a genetic propensity to run on carbs. I can almost guarantee, from past experiences with low-carb dieting, that I am one of these people. Furthermore, I can almost “feel” the stress on my body when I restrict carbs to any significant degree, and it has been shown in the scientific literature that low-carb diets can increase the release of cortisol, which may contribute to HPA-Axis dysregulation in susceptible individuals. That being said, people who are generally sedentary and suffer from blood sugar swings when eating a higher proportion of calories as carbs, may feel fantastic on a lower carb, or even ketogenic, diet. In this case they may be insulin resistant (induced or genetic), which does not allow them to handle a high, or even moderate carb, diet. There are also some people who seem to have the metabolic flexibility to do well and feel well regardless of whether they burning fat or glucose, but the take home point is that everything just discussed is very much to do with individuality – in the context of diet, there is no universal truth that is applicable to everyone. Ketosis may work wonderfully for some people, but terribly for others. If you do well on carbs, I do not see any reason to mess around with low-carb diets. If, however, you feel that you have some issues that you could potentially improve by trialling a well-designed low-carb/ketogenic diet for a period, then go ahead – you might be someone who will reap the benefits.

*note: I was going to provide more information on the topic of ketosis and athletic performance, but this blog entry is already longer than I had intended it to be. If you are interested in this topic, please follow the link to Alan Aragon’s debate with Jeff Volek at the NSCA’s 2013 Personal Trainer Conference. In brief, I agree with Alan. Although I believe that fat-burning can potentially be utilised successfully in low-glycolytic sports such as endurance running, I do not believe that they can work for high-glycolytic sports like football.


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