The high-fat, medium-protein, low-carbohydrate ketogenic diet has become a very popular conditioning tool for numerous local and international physique athletes because it has the power to incinerate fat while sparing muscle.
While not a new diet by any means, the rise in popularity of this diet has numerous athletes reconsidering their pre-contest diet options.
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Low-carb trigger
On a basic level, the diet forces the body to utilise fat stores rather than stored glycogen for fuel.
Due to the low carbohydrate intake prescribed by the diet, and in the absence of glycogen, the pancreas releases glucagon, a catabolic hormone that has the ability to break down body tissues for energy.
The body is then forced into a state of ketosis when glucagon and carnitine convert stored fat into free fatty acids and energy substrates called ketones or ketone bodies. This is all done in the liver through the Krebs cycle.
The ketone bodies then circulate and replace glucose as the body’s primary energy source, fulfilling the various vital functions that glucose had in the body. As the level of ketone bodies in the blood rise and reach a threshold, the body enters a state of ketosis.
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Keto dieting guidelines
The classic ketogenic diet excludes carbohydrate-rich foods such as starchy fruits and vegetables, bread, pasta, grains and sugar, while increasing the consumption of foods high in medium-chain triglycerides – which are more ketogenic – and long-chain triglycerides.
By forcing the body to tap into fat stores for energy by drastically reducing the amount of carbohydrates you consume, physique athletes have been able to drastically reduce their body fat percentages to dial in their contest conditioning.
By following this diet, even for short periods of time, the body also becomes more efficient at mobilising stored fat for energy.
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Muscle-sparing effect
Importantly for on-stage conditioning, a state of ketosis also seems to have a muscle-sparing effect, provided that your dietary protein intake and overall calorie consumption is sufficient and that training volume is kept low and heavy.
This happens as the body preferentially uses circulating ketones for energy, which limits protein gluconeogenesis – the process where muscle tissue is broken down (catabolised) into amino acids and converted into glucose.
Moreover, a lack of carbohydrates and sugar in the diet limits the amount of insulin released by the pancreas into the body. This can increase lipolysis and free glycerol release, and reduces fat storage. Reduced insulin release also helps to increase natural growth hormone production and releases other powerful growth factors.
A high-fat diet is also more calorie dense. The fact that every gram of fat released nine calories, as opposed to only four calories per gram of carbohydrate means that fat-derived energy is also more efficient and will help to increase energy levels.
Cycling your carbs
In terms of its application as a pre-contest diet, many coaches advocate the use of glycogen re-feeds or periods of carb cycling to provide the energy required to train at the correct intensity and volume in the lead-up to a show.
There are two specific techniques used in this regard, namely the cyclical (CKD) or targeted (TKD) ketogenic diet.
- CKDs include periods of high-carbohydrate intake for 1–2 days, usually over the weekend or on rest days, accompanied by a minimal amount of around 30-50g of carbohydrates on the other days of the week. These “carb-ups” refill your muscle glycogen stores, giving your body the energy it needs to perform the workouts in the week ahead. If done correctly, without causing a glycogen “spill-over” effect, this carb surge can cause an anabolic rebound and even muscle growth as the dieter comes out of the low-carbohydrate phase.
- TKDs schedule carbohydrate-rich meals before and after workouts. This approach is ideal for those intense training sessions where extra energy is needed. For instance, on heavy weight training days, an athlete might consume 25g of carbs with some whey protein 30 minutes before their workout and another 25–50g with protein afterwards. There are no carb-up days and carb intake is minimal for the remainder of the day.
Starting a ketogenic diet
If you have never used a ketogenic diet your body will have to go through a process commonly referred to as a “metabolic shift”.
This is the process whereby the body is weened off its reliance on glucose and learns to function properly using ketones as an energy source.
As glucose plays an important role in brain function dieters often experience cognitive fatigue, in addition to the physical fatigue associated with low glycogen levels. This process of adaptation can take up to three weeks, but if after three weeks your body hasn’t adapted then it is generally advised that you try another diet.
Generally, the best way to get into a state of ketosis is to start off with a fairly high fat intake with small amounts of protein.
First-time users should also aim to include 100g of carbs a day as part of their initial diet phase. The rest of their diet should consist of protein and fat.
Once your body acclimates to this type of eating, start reducing your carb intake until you reach a state of ketosis. At this point, reduce fat intake slightly and increase your protein intake.
It is important to do it this way as protein can impact the development of ketosis because a portion of your dietary protein intake can be converted into glucose.
The ideal ketogenic pre-contest diet usually consists of 35-40% of calories from protein, 50-55% from fat and the rest from carbs.
Author: Pedro van Gaalen
When he’s not writing about sport or health and fitness, Pedro is probably out training for his next marathon or ultra-marathon. He’s worked as a fitness professional and as a marketing and comms expert. He now combines his passions in his role as managing editor at Fitness magazine.
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