1. What is a Ketogenic diet?

A ketogenic diet is a diet with a very high fat content, moderate protein and very low carbohydrate content. There are variations on how the diet might be implemented, but on a typical ketogenic diet about 75-80% of your kcals come from fat and the rest from carbohydrate and protein.
Our bodies mainly use carbohydrate and fat for energy. When the diet is low in carbohydrate (or when you are starving/fasting or doing intense exercise) our bodies will produce ketones from fat. Some tissues like our nervous tissue and red blood cells can normally only use carbohydrate as energy. Ketones, unlike fatty acids, can cross the blood/brain barrier and therefore provide the brain with energy. If the concentration of ketones reaches a certain point we say the body is in a state of ketosis.
The diet was originally developed to treat epilepsy in children as ketones seem to reduce the occurrence of epileptic seizures. How ketones can suppress seizures is not exactly known and most of the research done has been completed using observation studies, which cannot show exact causation, only correlation.
The ketogenic diet is now popular for its alleged fat burning properties. The idea is that it gears your metabolism towards burning fat rather than carbohydrate and that this will aid fat loss. The critical point that is often, and conveniently left out, is that this will only work if you are in a calorie deficit, meaning you eat less calories than you burn. If you still eat as many calories as you burn you will not lose weight on a ketogenic diet.
2. What are the benefits?

If you are an epileptic child it may help control your epileptic seizures. If you are healthy and just looking to lose some weight there are none, really.
The ketogenic diet often appears to be more successful in weight loss trials on research with obese people. However, this is not consistently the case, and the difference tends to disappear if you’re looking at studies carried out over a longer period of time, looking at a wider spread of data. Much of the initial weight loss is water weight because to store carbohydrate in our muscles and liver, water is required. If you stop eating carbohydrate you also lose a lot of water. Having said this, there is some contradictory longer term research which does show greater fat loss on a ketogenic diet.
People also lose weight on a low fat diet or any other calorie restricted diet but when a low carb diet is compared to low fat it is often found to produce better results. In comparison to the Mediterranean diet (balanced macros, focus on healthy foods rather than macros) it seems to yield less impressive results. However, there isn’t a huge amount research that compares a ketogenic diet to a balanced, calorie restricted diet and the available research is not of good quality.
The benefits on health have also been investigated. High ketone concentrations seem to have a protective effect on cognitive function in the elderly. The ketogenic diet can help control metabolic diseases such as diabetes type 2, high blood pressure and high cholesterol levels. However, much of this is also a consequence of weight loss and I wouldn’t recommend trying a ketogenic diet to cure any of these diseases without the supervision of a health professional.
For the average person who’s just looking to lose some weight there is nothing that a ketogenic diet offers that a regular calorie restricted diet cannot. That is, unless you really love fatty foods. In that case it might be the diet of your dreams.
3. Can you give examples of some foods that fall into the Keto category?

Any food that has a high fat content and little of anything else basically, so things like olive oil, butter, avocados, fatty meats like beef and pork, salmon, eggs, nuts, peanut butter, cheese and cream. The only type of carbs you can really have in order to give your meals volume, and ensure you maintain a healthy micronutrient profile, are vegetables.
To give you an idea of how much you can have, consider the following example of a typical ketogenic diet. If you’re having 75% of calories from fat, 15% protein and 10% carbs, on a 2000 calorie diet, that works out at only 50g carbs per day, which is roughly the amount in a medium sized banana and apple, 5 digestive biscuits or one plain bagel.
4. What are some examples of food that a Keto diet eliminates?

Anything with a high carbohydrate content, so any starch, like potatoes, bread, rice and pasta but also sugar, alcohol and sweets. Lean protein sources also don’t really fit in, because often fats come paired with protein in foods. To meet your daily fat intake of 75% of your total daily calorie intake, it can be difficult to keep your protein intake low. There aren’t many foods that are 100% fat and to eat these foods all the time can be a struggle. To use the example diet again, 75% of 2000 calories is 167g fat which equates to around the amount of fat in 200g butter.
5. Are there negative side effects?

Chances are that your saturated fat intake will increase considerably on a ketogenic diet. Excessive intake of saturated fats has been linked to a number of diseases such as
Alzheimer’s, kidney disease and some types of cancer. However, research is not consistent in showing this correlation. Food choices may play a bigger role here.
The protein content of the diet is too low for most people, especially if you are training with weights and looking to retain or grow muscle mass. To use the example diet again, 15% of 2000 calories works out at only 75g protein. The recommended intake for protein ranges from 1.6-2.5 g per kg bodyweight per day. If you are in a calorie deficit and train with weights, you tend to be on the higher end of that recommendation and 75g is not going to be even close to enough. Even on the lower end of the recommendation, for example for a sedentary person who doesn’t train, 75g of protein will not cut it for most people.
The low carbohydrate content of a ketogenic diet means you have to cut out many types of fruit and vegetables which are higher in carbohydrate. Fruit and vegetables provide fibre, vitamins and minerals needed to stay healthy. Therefore being on a ketogenic diet for a long time can lead to constipation and micronutrient deficiencies. Subjects in low carb interventions have reported low fibre intakes. The recommended intake of fibre is 30g for adults, this is difficult to obtain from only 50g carbs.
Apart from that, if you are in a calorie deficit you will be hungry at some point. To counteract that you want to eat satiating foods that keep you full for longer. Protein and fibre rich foods do exactly that, but you need to limit your intake of these on a ketogenic diet.
Furthermore, if taken to the extreme, there is a risk of developing a condition called ketoacidosis. This occurs when the concentration of ketones becomes too high and lowers the pH of the blood. In other words, your blood gets too acidic and this can be very dangerous.
6. How does a Keto diet affect physical performance and energy levels?

Carbohydrate is the preferred fuel for our muscles. If you’re doing a lot of training, your performance will probably suffer with a lack of these. There will always be some individual variability. Some people cope better with lower amounts of carbs than others but overall performance will not be as strong without carbs as with carbs for most people. It depends what type of exercise you are doing as our bodies use fats and carbohydrates differently depending on the exercise intensity. Weightlifting performance doesn’t seem to suffer as much as endurance performance, for example cycling and running..
Experiments on sports performance don’t show a detrimental effect of the ketogenic diet. Our bodies seem to be able to adapt quite well. However, there isn’t much available and the research that has been done is often done on small test groups. In larger trials, not looking at sports performance subjects alone, findings often report low mood and fatigue as side effects of the diet. If you are trying to lose weight, this works against you. Exercise is an essential part of staying healthy and it can help to add to your calorie deficit on a fat loss diet. However, if you don’t have the energy to train, you will be less active and burn less calories which in turn jeopardises your calorie deficit.
7. In terms of practicality, how easy is it to follow a Keto lifestyle?

A ketogenic diet is very difficult to sustain because it is very restrictive. The food options are limited, so you’ll need to eat the same few foods over and over again. This is difficult for most people as variety is indeed the spice of life.
8. Are there any people who shouldn’t adopt a Keto diet?

Most people. Unless you are an epileptic child, this diet probably isn’t for you.
9. Would you recommend the diet on the whole?

No, any diet that simply cuts out a macro or food group is not something I’d ever recommend. It’s unsustainable and unnecessary. The ketogenic diet combined with a calorie deficit offers no advantage to a regular individual over a normal calorie restricted diet where you get a balanced intake of protein, carbohydrate and fats.. If anything, the ketogenic diet is probably worse due to the low protein content, lack of variety and lack of fibre to keep you feeling full, therefore potentially having a negative effect on training.
Nutrition and dieting are not complicated. To lose weight you simply need to be in a calorie deficit for a prolonged period of time. The main reason why people fail to lose weight and keep it off is because they are not consistent. I understand, dieting by definition is difficult because we have developed a brain that is focused on preventing starvation. Dieting is essentially nothing more than systematically starving yourself. There’s always a gap between science and reality. What is most effective according to science may not be realistic for many people and I think this is certainly the case for the ketogenic diet. In many of the trials, dropout rates are seen to be as high as 30-50%, with dropout rates in the lower carb group being the highest. Even amongst epileptic children who use the diet to cope with their seizures compliance is reportedly low. The ketogenic diet can help you lose weight but like any restrictive diet, most people cannot keep it up long term, which is what is needed for lasting results.
So, my advice would be to focus on making lifestyle changes rather than following an extreme diet as a ‘quick fix’. What tends to work best, is creating a calorie deficit by eating slightly less calories than you need, and exercising to build muscle and increase the number of calories you burn. Eat a diet based on whole foods with sufficient protein, vegetables and fibre and have your alcohol and treats in moderation.

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