Keto Transition Guide for Athletes

Posted by Josh Gape on

If you’re an athlete embarking on your keto transition, you’ve come to the right place.


The classic ketogenic diet (90% fat, 6% protein and 4% carbohydrates) does not provide enough protein for athletes to maintain the level of muscle mass required for performance. For consistent results in the elite arena, a modified ketogenic diet consisting of roughly 70% fat, 25% protein and 5% carbohydrates is recommended.


Simply put, to be in ketosis your body must be producing ketones. To really start feeling the benefits, most experts agree you need to have blood ketone levels of 0.5mmol/L or over. This can be achieved through diet, supplementation, fasting and exercise. However, to get the most out of ketosis, I believe a combination of these four approaches works best, with the ketogenic diet being the cornerstone. When eating this way (in the absence of carbohydrates), your body begins to break down stored and dietary fat into ketone bodies, which are used as your primary fuel source.


Like the idea but don’t know where to start? We’ve got you covered with our guide on how to transition from a carbohydrate rich diet to a ketogenic diet as efficiently as possible. 


The ease in which an athlete can transition into ketosis varies from person to person. Factors such as current diet and level of fat adaptation (your body’s ability to utilise fat for energy) play key roles. If you’ve traditionally eaten a carbohydrate rich diet, you’re unlikely to be very fat adapted and, therefore, you need to train your body to burn fat as opposed to carbohydrates for fuel.


This transition period is often associated with ‘keto flu’. The symptoms, such as brain fog, hunger and loss of energy can derail the ketogenic lifestyle before it has even started. During this period the body hasn’t yet become efficient at utilising fat for fuel and is also without the carbohydrates it has relied on for so long. Under these pressures, your body may well try to create glucose from stored protein through a process called gluconeogenesis, breaking down hard earned muscle to be used as energy. Definitely something you want to avoid if you plan to maintain your training level whilst becoming fat adapted. To prevent this, keep protein intake high during the first three weeks of ketogenic dieting. 


By providing this protein boost, you’ll prevent muscle wastage but your body will also convert some of this dietary protein into glucose through gluconeogenesis. This will limit your ability to get deeply in to ketosis, as your raised glucose levels (from protein) will provide a fuel source and therefore decrease your body’s requirement for, and production of, ketones.


After a period of 4 – 8 weeks, your body will be fully fat adapted and begin producing ketones. At this stage, you will be able to reduce protein intake without losing muscle mass. This is because ketones have a protein sparing effect. When in ketosis, your body begins to recycle key Branched Chain Amino Acids (BCAAs) such as Leucine, which are the building blocks for protein synthesis. Taking less protein in through diet once you’re producing ketones, decreases the likelihood of gluconeogenesis without jeopardising your hard-fought gains. The goal is to find the sweet spot, where you can still maintain or increase muscle mass (depending on your goal), whilst also producing the greatest number of ketones.


If you are able to get deep into ketosis even when consuming high amounts of protein then great. If not, once fat adapted, you can then begin to reduce protein intake steadily, whilst monitoring your muscle mass and ketone production.


In summary, it’s important to slowly teach your body to become more capable at burning fat for fuel, whilst maintaining muscle mass. Over the first three weeks, I suggest keeping protein intake high at 25% of total calories, whilst reducing carbohydrates down to 25 - 50g (3 – 7%) per day and steadily increasing fat intake. Once in a ketogenic state, you can then look to further decrease your protein intake, whilst increasing fat consumption. Monitoring your ketones, health, performance, weight etc. during this time will enable you to dial in on the ketogenic diet approach that is optimal for you.


Note - I would also suggest starting to add Medium Chain Triglycerides (MCTs) in to your diet. For a Ketogenic athlete, MCTs are the best option if you’re looking for something derived from real foods and you require an immediate energy boost. However, overdoing it can result in a dash to the nearest toilet, therefore I recommend steadily increasing your intake over time.


Mapping it Out

First things first, you need to work out your daily macronutrient requirements (the level of protein, carbs and fat) you need to achieve your goal.


To do this, I use the Keto Calculator:


Using myself as an example, my daily calorie intake to maintain weight is 2,677kcal per day. However, I’m trying to gain weight so I’m eating a 10% calorie surplus per day taking my total figure to 2,945kcal. If you’re looking to lose weight you can calculate in a 10% calorie deficit instead. If you find it difficult to eat much more or less, I’d opt for a 5% increase or decrease. However, if you find it easy, I still wouldn’t recommend over a 10% change.


Before starting my transition to ketosis, my daily macro target was:


Protein = 182G (728kcal) - 25% of daily calories 

Carbs = 256G (1,024kcal) - 35% of daily calories

Fat = 133G (1,193kcal) - 40% of daily calories

Total = 2,945kcals


*Note - Protein and carbs are 4kcals per gram, whereas fat is 9kcals per gram. 


Transition Week 1

As discussed above, I’m keeping protein high, whilst adjusting fats up and carbohydrates down.


Protein = 182G (728kcal) - 25% of daily calories

Carbs = 150G (600kcal) - 20% of daily calories

Fat = 180G (1,617kcal) - 55% of daily calories [10g from C8 and / or C10 MCT oil]


*Note - carbohydrates should be counted subtracting fibre (this is already done for you in the UK but not in the US). For example if you eat something which contains 14g of carbs, 3g of which are fibre, only count this as 11g towards your total daily carb intake. The exception to this rule is synthetic carbs such as IMO fibres, which are found in the majority of energy bars out there. A number of studies are showing that, although these are classified as fibre, they do impact blood glucose levels and therefore shouldn’t be counted as such. Regardless, I highly recommend avoiding these completely as they have no micronutrient value and instead opt for real, earth-grown food sources. Your carbs should come from mainly vegetables (preferably leafy green due to high fibre and nutrient content), some nuts and seeds and a small portion of fruit. I mainly opt for berries due to their high micronutrient content and low glycemic response.


Transition Week 2

Protein = 182G (728kcal) - 25% of daily calories

Carbs = 100G (400kcal) - 14% of daily calories

Fat = 202G (1,817kcal) - 61% of daily calories [15g from C8 and / or C10 MCT oil]


*Note - If you change weight at any point, you will need to re-calculate your numbers and adjust your diet accordingly using the calculator. 


Transition Week 3

Protein = 182G (728kcal) - 25% of daily calories

Carbs = 50G (200kcal) - 7% of daily calories

Fat = 224G (2,017kcal) - 68% of daily calories [20g from C8 and / or C10 MCT oil]


At this point I would review your progress, including; your weight and performance goals, general health (how have you been sleeping etc.), cognition and ketone levels. If you decide that you still want to try to increase your ketones levels, you should begin to raise your fat intake, decreasing carbohydrate and protein consumption. As stated earlier, you want to try and find the sweet spot where you’re optimising health and performance.


Ketosis Week 1

Protein = 160G (640kcal) - 22% of daily calories

Carbs = 50G (200kcal) - 7% of daily calories

Fat = 234G (2,105kcal) – 71% of daily calories


*Note - For athletes, I generally recommend not to take protein consumption below the 1.5g per kg of total body weight mark even once fully fat adapted to ensure you have enough protein for muscle maintenance and recovery. In this example that would be 138g (19% of total kcals).