The Ketogenic Diet is a nutritional strategy based on reducing as much as possible the amount of carbohydrates in food so that our health “works” with fat.
As most of us know, carbohydrate-rich foods are currently the most talked about topic in the world of performance and health nutrition, among which we find great professionals such as Layne Norton or Alan Aragon or critics of the calibre of Jeff Volek or Jacob Wilson.
What is the Keto diet?
A little further above, we have commented that it refers to a nutritional strategy following a low-carbohydrates (“low carb”) diet based on high-fat foods.
The word “keto” comes from the term “ketone” (keto –> ketones), and is due to the fact that through this type of diet we will experience a series of effects where our body will “function” with a type of molecules known as ketones.
It can be said that it is a fuel alternative to glucose, hence the hypothesis of the relationship between its effects and health. Ketones are produced when our intake of carbohydrates (glucose) is considerably reduced, in keto or low-carb type diets.
It is the liver that produces the ketone bodies from the fats that will serve as energy throughout the body and especially in the brain.
Our brain consumes a lot of energy, but not directly from fat, but from ketones…
What happens when we follow a keto diet?
Our whole body changes the metabolic mode of functioning towards fat. “We burn fat 24/7, and can lose weight quickly. We say then that we are in ketosis.
Even if the insulin is kept very low, and “fat burning” is enhanced, it should be noted that there will always be a calorie deficit for weight loss.
However, it should also be noted that to lose weight (fat), if we opt for a keto diet, we probably manage the anxiety and cravings for sweets that are also frequent in a diet that is not low in carbohydrates better.
Ketoacidosis is NOT ketosis
This is often one of the most common mistakes made when interpreting a low-carb diet.
How ketoacidosis occurs
Ketoacidosis is a process that occurs in diabetics because glucose cannot enter the cell
So there is an increase in ketones to levels that are harmful to our health.
As we can see in the picture, the glucose does not reach the cells producing a high concentration of glucose in the blood (high blood sugar)
To provide this energy to the cells, the adipose tissue (fat) breaks down the fat and releases it into the bloodstream, which when filtered in the kidney also produces alterations in the fluid balance due to the high concentration in both (osmosis).
How Ketosis happens
On the other hand, we have ketosis, a process that occurs naturally when glycogen levels are lowered over a long period of time, for example with a keto diet.
The difference is that in ketosis the entry of glucose into the cell is not altered, the levels of insulin remain stable and functional, and so the number of ketone bodies is lower.
Ketosis is not synonymous to ketoacidosis.
Interestingly, these levels are optimal for the body to function properly
How long does it take to get into ketosis?
According to proponents of the keto diet, it takes about 4 weeks for your body to fully adapt to using fat as fuel, and you may consume small amounts of carbohydrates, even in keto, mainly from vegetables.
In this way, in that time you will become a body fat burning machine.
This sounds really good, however, after that time you will not become a Super Saiyan keto.
Before we see the studies that defend this, we have to see the reasoning behind it. The theory is that by oxidising glucose all our lives due to the high amount of carbohydrates in the diet, your body loses efficiency when it wants to use fat as an energy source.
This is true, as you are continually on a high carbohydrate diet, the number of glycolytic enzymes (proteins related to glucose metabolism) is increased. This causes a loss of metabolic flexibility, or in other words, the ability to effectively alternate fat or glucose as fuel.
Even with 48 hours of fasting, increased enzymatic activity on fat metabolism is observed (7).
This reflects the fact that it doesn’t take a month for the body to improve its use of fat as fuel, as even the simple fact of being on a high-fat diet with a calorie deficit facilitates this metabolism even in sedentary people (8), as shown in the image below:
Keto diet for athletes?
We will take as an example the following study (9) where untrained obese subjects followed a diet for 6 weeks based on lean meat, fish or poultry, and vegetables compared to a group that consumed 45% carbohydrates 40% fat and 15% protein.
The result was as follows:
The group that followed a non-carbohydrate diet obtained higher levels of ketones, which does not occur in the control diet (Base Line).
However, the detail that surprised me most was that those doing ketosis had lower levels of T3 (metabolism-related thyroid hormone), as well as higher levels of reverse triiodothyroxine, worsening T3 activity.
In terms of performance, a better time was observed after these 4 weeks, which would confirm the theory of ketogenic adaptation.
However, this improvement is independent of the amount of glycogen they had, as I must remember that they were NOT trained subjects, so the improvement could have been due to the simple fact of moving from a totally sedentary state to moving.
Moreover, if we look at the study we see that at no time was the intensity of the diet elevated to a high state, which is where the ketogenic diet really gives problems. At low intensities, the main fuel is usually fat, unless in pre-workout we have consumed a large amount of glucose.
The author of the study himself commented as follows:
The cycling subjects in this study observed a slight decrease in their energy level, while in Inuit diet training, their ability to sprint was limited during the period of carbohydrate restriction.
This shows that ketone bodies are not suitable for athletes seeking explosive movements over a moderate to long period of time or even for long-distance athletes.
This is reflected in the elite Ethiopian runners (best brands worldwide), basing their diet on 64% carbohydrates(10)
Ketogenic diets make you lose more fat
Leaving aside the “ketones kill your brain”, this is possibly the most widespread myth on this subject
Let me explain: When we look at the studies conducted on this topic, we see that keto diets result in greater fat and weight loss than high carbohydrate diets.
This is because as a rule, keto diets tend to be higher in protein-rich foods than in carbohydrates, being 25-30% vs 15% in most cases of the daily total.
Due to the thermogenic and muscle protective effect of protein, a better body composition with ketogenic diets is observed.
PROTEINS + CALORIC DEFICIT= YOU LOSE FAT!!!!
What conclusions can we make
The reason why ketogenic diets lead to greater weight loss is water loss
As we know, glucose is stored in the muscle in the form of glycogen, which carries a significant amount of water into the cell.
As the days pass without ingesting carbohydrates, this glycogen is used and a significant amount of weight is lost in the first 3 days.
This is why many people find themselves with deflated muscles in the peak week on a ketogenic diet.
- Diabetic ketoacidosis. H.E. Lebovitz, MD
- Factors associated with brain herniation in the treatment of diabetic ketoacidosis. MD Stephen C. Duck, MD David T. Wyatt
- Risk Factors for Cerebral Edema in Children with Diabetic Ketoacidosis. Nicole Glaser, M.D., Peter Barnett, M.B., B.S., Ian McCaslin
- Adherence to insulin treatment, glycaemic control, and ketoacidosis in insulin-dependent diabetes mellitus. MD Andrew D Morrisa
- Diabetic ketoacidosis in a community-based population. Johnson DD, Palumbo PJ, Chu CP.
- Plasma Amino Acid Levels in Diabetic Ketoacidosis. Philip Felig, M.D., Errol Marliss, M.D., John L Ohman, M.D. and George F Cahill Jr, M.D.
- Hormone-sensitive lipase-independent adipocyte lipolysis during beta-adrenergic stimulation, fasting, and dietary fat loading. Fortier M1, Wang SP, Mauriège P, Semache M, Mfuma L, Li H, Levy E, Richard D, Mitchell GA.
- Increased adipose tissue lipolysis after a 2-week high-fat diet in sedentary overweight/obese men. Howe HR 3rd1, Heidal K, Choi MD, Kraus RM, Boyle K, Hickner RC.
- Capacity for moderate exercise in obese subjects after adaptation to a hypocaloric, ketogenic diet. Phinney SD, Horton ES, Sims EA, Hanson JS, Danforth E Jr, LaGrange BM.
- Food and macronutrient intake of elite Ethiopian distance runners. Lukas Y Beis1, Lena Willkomm2, Ramzy Ross1, Zeru Bekele3, Bezabhe Wolde3, Barry Fudge4 and Yannis P Pitsiladis1*
- Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. Sacks FM1
- Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors: a meta-analysis of randomized controlled clinical trials. Hu T1, Mills KT, Yao L, Demanelis K, Eloustaz M, Yancy WS Jr, Kelly TN, He J, Bazzano LA.
- Similar weight loss with low- or high-carbohydrate diets. A Golay, A F Allaz, Y Morel, N de Tonnac, S Tankova, and G Reaven
- How does the Keto diet affect the intestinal microbiome?
- Keto diet in strength sports
- Metabolic Flexibility: How to adjust your diet and improve performance