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The Ketogenic Diet -Pros & Cons!


The Ketogenic diet is big news and quite a controversial subject with many people swearing by it and others totally against.

I'd like to give as balanced a view as possible and outline the pro's and con's to this method of eating.

During normal metabolism, glucose is the preferred fuel for the body especially the brain, infact it's the only fuel source to pass through the blood brain barrier apart from ketones (but we'll come to that) When glucose intake levels are low (from a very low carb or Ketogenic diet), glycogen from the liver (stored glucose) as well as fatty and amino acids are released to fill the gap.

Once glycogen is depleted, more protein is released for conversion to glucose, because many tissues especially the brain are unable to use free fatty acids as fuel.

Over time Free fatty acids metabolism in the liver is altered slightly so that some amount of Acetyl CoA produced is condensed to make ketone bodies. This normally takes approximately three days to achieve.

In the initial 3 weeks of ketosis, protein is used alongside ketones to fuel the brain.

After this time, ketones provide 75% of what it needs while various by products of triglyceride metabolism pick up most of the slack. This prevents protein breakdown continuing and is a ketogenic state.


Contrary to popular belief, consuming protein to a sufficient level will not impair the onset of ketosis, but will mediate the amount of protein that must be broken down for the purpose of glucose production.


A ketogenic diet can be set up first by calculating calorie needs, then making these up with adequete protein, up to 30g of carbohydrates and the rest being dietary fat.

At the end of the day a very low carb diet still needs to have an energy balance, if you consume 190g of fat but only burn 150g you will still store 40g of fat.

Now lets have a look at the impact it can have on various different goals-


Keto and fat loss- Ketosis lowers insulin, the storing hormone. However insulin is not responsible for fat gain, fat can still be stored by being transported by chylomicrons via your lymph system.

There is a question of a metabolic advantage as acetate (one of the three components of a ketone) is removed from the body via breath and urine at a cost of approx 80-100kcals a day but not hugely significant.

Rapid weight loss is usual at the beginning of a ketogenic diet but this is mainly water as glycogen stores a depleted. However this can increase motivation for the individual to continue with their weight loss journey.

It has also been shown to reduce hunger which can obviously make dieting easier with an increased ability to fast due to glucose in the blood being flat lined anyway so no spikes and dips with blood sugar levels to deal with.

The restriction on hyper pallatable foods can also have a positive impact as well as less food pre-occupation. This is not for everyone though as it is a very restrictive diet and the individual may crave carbohydrate rich foods.

It is also important to salt your food and maybe incorperate electrolytes into your diet as reduced glycogen stores may lead to dehydration.


Keto and sports- Keto diets have shown to be beneficial for ultra marathon runners as these individuals tend not to go higher than 65% max heart rate and generally tend to use only type 1 and type 11a muscle fibres (these can be fueled by ketones)


For most other sports this is usually not the case and it can impair power and strength.

Any sport which pushes us into an anaerobic state (over 65% Max HR) needs glucose for fuel. Type 11b muscle fibres used for power and growth need glocuse for fuel, ketones do not assist with this muscle fibre at all so can impead performance in your chosen sport.


Resistance training usually lies within 65-85% max heart rate and uses type1 and type 11a muscle fibres. Once extra power is required type 11b muscle fibres are recruited. However this cannot occur without the presence of glucose and will hold back hypertrophy.


So how can we modify this for performance purposes?-

A proven method is to consume 30-50g of carbohydrates (in the form of glucose) immediately before your activity. You will use it as fuel and so don't leave ketosis.

Another method is the cyclical keto diet- This involves sticking to keto throughout the week and then going very high carb,relativley low protein, low fat at the weekend to help performance goals. However this may lead to a binge, restrict cycle so use with caution.


Keto and your overall health-

The keto diet can increase LDL cholesterol while HDL can sometimes go up too.

Fibre can be low on this diet with carbohydrates being so low (therefor fruit and vegetable consumption) and is very important for our dietary needs as well as micronutrients.If following the ketogenic diet consider a good quality multi-vitamin and get as many veggies in as possible, dark leafy greens are pretty low in carbs for example.

The keto diet may be beneficial with type11 diabetes due to the lowered insulin and glucose in the blood. However type 11 diabetes can be linked to kidney disfunction so should be looked at before considering this method as it will put some pressure on the kidneys if they are not working to their potential.

A less aggresive low carb diet may be preferable.


With all this being said the ketogenic diet is a tool and can help increase adherence due to the affects mentioned above which may lead to fat loss improvements.However the ketogenic diet does not have any metabolic change of any significance and a calorie deficit is still required for fat loss.

Personally I love my Carbs too much to sacrifice a large portion of them but if you are curious maybe give it a go and see how you feel.



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