By Myprotein Writer |
The Ketogenic Diet or – Keto Diet – limits carbohydrate intake to around 50g per day or 5% energy intake – whereas a low-carb diet has no definition. Personal perceptions of low carb may be completely different to another person’s.
In fact, on a ketogenic diet, the macronutrient content would be similar to like 5% carbs, 15% protein and 80% fat. This is according what we are currently giving people for a research study we are running at Anglia Ruskin University, Cambridge.
This is the key difference between going keto and low carb, as this very limited amount of carbohydrate depletes the body and brain of glucose. This is where “keto-adaption” takes place and the body shifts away from carbohydrate metabolism and towards predominantly fat metabolism both at rest and during exercise.
However, the central nervous system and brain cannot do this as fatty acids cannot cross the blood-brain barrier and therefore the increase of blood ketones (b-hydroxybutyrate, acetoacetate and acetone) reaches concentrations of 2mmol/l or more. This is why for the first few days on the diet you may feel tired, lethargic and lacking concentration.
Ketosis & Ketones
Ketone bodies are a major source of energy during periods of fasting or severe carbohydrate restriction (<50g) per day and are produced mainly in the liver.
Originally thought of as just a metabolite; ketones may serve an important role linked with the increase of particular enzymes regulating endurance training adaptations.
In addition, ketones may even play a role in influencing food intake control by affecting specific parts of the brain that regulate this (the hypothalamus) as well as the way they interact with hunger regulating hormones such as ghrelin.
A carbohydrate intake greater than 50g will be very likely to prevent ketosis and keto-adaptation. However, a protein intake greater than 25% will also do this due to some of the Amino Acids (multiple amino acids form proteins and act as building blocks for the body) being converted to glucose.
Therefore, it is just as important to modify the protein content of the diet as it is the carbohydrate content if you want a true ketogenic diet and “fat adapted” athlete.
‘Keto’ or ‘Low-Carb’ Diets for Endurance Training
The main goal of any endurance training programme is to enhance the fat burning capacity of the muscle as it is suggested this will enhance exercise performance. The ketogenic diet and low carb diets for that matter will both do this but there is no evidence which shows this improves performance.
For example: we have shown in our lab that just 10-days on a ketogenic diet will quadruple the amount of fat burnt during exercise but the implications that this translates to better performance is purely speculative.
Some also suggest that this increase in fat burning will lead to increased weight loss; however it is currently accepted that unless a calorie deficit is present then weight loss will not occur.
This is a question we will be addressing in our work when we compare two ketogenic diets of different calorie values. One possessing energy balance and the other a negative energy balance. According to current evidence, only the negative energy ketogenic diet should result in weight loss.
Benefits & Applications
The ketogenic diet appears very efficient at inducing weight loss over a short period of time and has been used for weight making in sports such as gymnastics and taekwondo.
An added benefit of the ketogenic diet is the high-protein content and providing it contains protein of ~1.5g/kg bodyweight muscle mass and strength can be preserved whilst simultaneously losing body fat.
It has also been observed that carbohydrate restricted diets and ketogenic diets can enhance endurance training muscle adaptations by “switching on” key metabolic switches to a greater extent.
Take Home Message
In conclusion, low carb diets appear to have use in sport but the application of the ketogenic diet needs establishing further.