The Ketogenic Diet - What you need to know

Jan 10, 2020
Posted by: Monique Parker


‘New Year – New You’, New Year’s resolutions, detox programmes, and of course diets…. social media has been overloaded with all this and as a nutritionist, I have had several queries about the subject too. Which detox products to use, what diet to follow etc.

To be clear, I don’t really believe in New Year’s resolutions. In my opinion, every day is a new day, and to only use January as the start for positive changes will reduce the chance of long-term success. Of course, it is a natural reaction that after over-eating at Christmas, you would like to cut down and improve your diet again.

I also don’t really like the word ‘diet’. Good old Wikipedia says “the word diet often implies the use of specific intake of nutrition for health or weight-management reasons”.  I rather talk about lifestyle change, changing the way you eat, not just for a couple of weeks or months, but for a lifetime. Finding the foods that will benefit your health and wellbeing. This is of course different for each individual. And that is one of the reasons I would never recommend one particular way of eating.

Last year, one of the buzzwords in nutrition was 'ketogenic diet'. I get a lot of questions about this diet and I thought this time of year would be a good moment to share some information on this way of eating.

When you google ‘ketogenic diet’ you will get almost 50 million results. There sure is a lot of information on the internet. But when you ask people if they know what a ketogenic diet is and how it works, not everyone can give you an answer.

Early 2019, the ITV programme ‘Save Money Lose Weight’ put several diets in the spotlight and looked at which one was best £ for lbs and had the best results. The Vegan Keto Diet came second after Lisa Riley’s Honesty Diet. So, what is so special about this diet that has been embraced by dieters all over the world, often with very good results?



A ketogenic dIet is a diet that is high in fat, moderate in protein and low in carbohydrates. The reduction in carbohydrates tricks your body into thinking it’s starving.

When you eat carbohydrates, they are turned into glucose (sugar), which is released into the bloodstream. When your blood sugar goes up, insulin is released, and it’ll distribute the glucose to the cells. Your body’s cells need energy and most cells prefer to use glucose. If there is excess glucose, i.e. after a high carb meal, it is converted into fat in the liver. The fat is then stored in the body’s fat cells. 

If there isn’t any glucose around, the body starts to burn fat for energy.
This is all good for your muscles, but not for your brain, as it cannot convert fat into energy. Given the brain is your most energy-hungry organ, this is a problem. The brain uses about 20% of the body’s energy. Luckily there is always enough glucose stored to keep your brain happy for a couple of days.

And this is where ketones come in.

The liver can convert fat (fatty acids) into compounds called ketone bodies (ketones), which enter the blood stream and are used as ‘fuel’ for the brain, but also by other organs such as the heart and skeletal muscles.

So, when you reduce carbohydrates and your blood sugar level goes down and there is no excess glucose to store as fat, the body becomes very efficient at burning fat for ‘fuel’ for the cells and converting stored fat into ketones in the liver so the brain will have a ‘fuel’ supply too.

A ketogenic diet is effective for weight loss[i] as long as you get it right. But weight loss is not the only result people can get from dramatically reducing carbohydrates and upping the fat intake. The diet can also have an impact on risk factors for disease such as metabolic syndrome, type 2 diabetes[ii] [iii], insulin resistance and Polycystic Ovarian Syndrome. Apart from improving insulin sensitivity and blood sugar levels, the diet also seems to positively affect cholesterol levels, triglycerides and blood pressure.[iv]

The diet has appetite-suppressing powers that are possibly linked to changes in appetite-regulating hormones such as leptin, but also because fat and protein make you feel fuller.

Impressed? Funnily enough, the ketogenic diet is not new at all. For almost a hundred years it has been used to treat drug-resistant epilepsy, especially in children.[v]

What can you eat?

Your diet should consist of 60-80% fat, 15-30% protein and 5-10% carbohydrates.

A typical keto menu:

Breakfast – eggs, avocado, smoked salmon and spinach or rocket

Lunch – Big salad with lots of greens, a good drizzle of olive oil, and some protein (meat, fish etc.)

Dinner – Homemade chicken curry with green salad (ready curry sauces will have too many carbs and home-made will taste much better!)


It normally takes about 3 days of eating 20-30 grams of carbs per day, before you go into ‘ketosis’ (when you start to produce ketones). But don’t forget that this is very individual and for some people it can take longer.

Most people use a weight loss or food tracking app such as MyFitnessPal, Senza, Carb Manager or Ketodiet, to work out the right amounts of fat, protein and carbs.


Is the ketogenic diet for everyone? [vi] [vii]

The ketogenic diet is definitely not for everyone, not just because there is no diet that fits all, but also because there are cases where a ketogenic diet could be harmful:

  1. When you’re pregnant
    The foetus needs carbohydrates for brain development and growth
  2. When you have an underactive thyroid[viii]

You need to eat a moderate amount of carbohydrates because insulin is needed for the conversion of thyroid hormones

  1. If you’re suffering from adrenal fatigue
    A low-carb diet can cause extra stress to the body
  2. If you have gut issues
    A long-term very low carb diet could change the gut flora, because the diet is generally low in fibre (no grains, less vegetables etc.)
  3. If you have any inflammatory problem, i.e. auto-immune disease, inflammatory bowel disease, coeliac disease etc.
    As the diet can be inflammatory, you don’t want to add to existing inflammation in your body


Let’s start with the pros of the ketogenic diet[ix]:

  • Increased fat burning
  • Positive changes in hunger hormones such as leptin and ghrelin
  • Fat and protein make you feel full for longer
  • Reduced appetite
  • Improves blood sugar control
  • Effective for lowering insulin levels
  • Can reduce cholesterol levels and triglycerides
  • Can help lower blood pressure
  • By dramatically reducing carbs you will cut out possible allergens such as gluten


Unfortunately, there are quite a few cons too[x]

  • There is not much known about its long-term effect
  • It is quite hard to follow, especially if you don’t like fatty food
  • There is a slight risk of becoming obsessed with dieting as you’ll need to keep track of what you’re eating to make sure you get the ratio fat-protein-carbs right
  • Athletes need to be careful and test it first as it could affect performance and recovery
  • Some people might have a fat-phobia as for years fat has been portraited as the ‘baddy’, especially when it comes to weight
  • Risk of overdoing it with protein which could affect the kidneys[xi]
  • Focussing on a limited amount of foods. Diversity in the diet is important for everybody
  • Social pressure, especially when you’re socialising with friends and family and they don’t understand your diet
  • Side-effects such as keto flu (low energy, headaches, body aches, brain fog, tummy trouble etc.) and electrolytes imbalance (less carbs means more electrolytes such as sodium, potassium and magnesium being excreted in the urine – electrolytes are crucial for the body)
  • Especially for people who are eating a lot of fruit and vegetables because of their health benefits, the ketogenic diet can feel a bit ‘unnatural’ as fruit is very limited, and you have to be very careful with vegetables (green leafy vegetables are the least problematic)


Tempted to try the ketogenic diet? Make sure you are informed and do it the right way. And if you have any health issues, please check with your GP if it is ok to do the diet.



Sarah didn’t have to lose weight but was pre-diabetic, her cholesterol and triglycerides were high, and she was on blood pressure tablets. Sarah decided to see a doctor privately, given her family medical history of diabetes and cardiovascular disease. This doctor recommended the ketogenic diet to her. Sceptical at first, Sarah decided to give it a go and see what would happen. She had no expectations.

After a week of ‘keto flu’, Sarah was about to give up, but then a family member got very ill and this was the push she needed to continue. Getting used to the diet was not a problem as she managed to find keto-friendly foods she liked. Her morning bullet-proof coffee became her treat of the day. Sarah did lose a bit of weight, but nothing too dramatic, and she also lost some stubborn fat around her middle, very quickly.

A couple weeks into the diet, Sarah started to feel faint and had difficulty concentrating. When her blood pressure was checked, it turned out to be quite low, which was unusual for her as she was taking a low dose of blood pressure medication. It turned out to be a common side-effect of the diet: dehydration and a shortage of electrolytes. After increasing her fluid intake and adding some electrolytes to her water, she started to feel a bit better. Sarah was also slowly reducing her blood pressure medication, under supervision of her doctor.

After about six weeks, her doctor repeated the blood tests she did before she started the diet and the results were remarkable. Her insulin, blood sugar, cholesterol and triglycerides were now all within the normal range. In the meantime, she had come off the blood pressure medication completely.

You would expect Sarah to continue the diet, given the positive changes.

However, her energy levels had not increased at all, and she was often feeling quite low and anxious. She first thought this was due to stress in her life, but after slightly increasing her carbohydrate intake, she started feeling a lot better. She also found it very difficult to follow in a social setting. Going out for lunch with her friends was not always easy and her family often commented on, what they thought, her restrictive food pattern. And if she ate something that wasn’t ‘keto’, she would feel bad.

A strict ketogenic diet was apparently not 100% suitable for Sarah.[xii] With the knowledge she gained from her experience, she is now eating a healthy diet with unprocessed foods, good quality protein, healthy fats and low-moderate carbohydrates (mostly low GL)[xiii] and she tries to adhere to 12-14 hours overnight fasting.[xiv]




[i] Paoli, A et al. (2013). Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. European Journal of Clinical Nutrition. 67, 789–796.

[ii] Feinman, R et al. (2015). Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base. Nutrition. 31 (1), 1-13. (abstract)

[iii] Unwin, D & Unwin, J.  Low carbohydrate diet to achieve weight loss and improve HbA1c in type 2 diabetes and pre-diabetes: experience from one general practice. Practical Diabetes (2014), vol 31(2):76–79.

[iv] Schugar, R & Crawford, P. (2012). Low-carbohydrate ketogenic diets, glucose homeostasis, and nonalcoholic fatty liver disease. Current Opinion in Clinical Nutrition and Metabolic Care. 15 (4), 374–380.

[v] Kossoff, E et al. (2018). Optimal clinical management of children receiving dietary therapies for epilepsy: Updated recommendations of the International Ketogenic Diet Study Group. Epilepsia Open. 3 (2), 175–192.

[vi] Kresser, C. (2019). Is a Low-Carb Diet Ruining Your Health?. Available: Last accessed 2019-09-22.

[vii] Ullrich, I et al. (1985). Effect of low-carbohydrate diets high in either fat or protein on thyroid function, plasma insulin, glucose, and triglycerides in healthy young adults. Journal of the American College of Nutrition. 4 (4), 451-459.

[viii] Spaulding, S et al. (1976). Effect of caloric restriction and dietary composition of serum T3 and reverse T3 in man. The Journal of Clinical Endocrinology and Metabolism. 42 (1), 197-200.

[ix] Noakes, T & Windt, J. (2017). Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review. British Journal of Sports Medicine. 51 (2), 133-139.

[x] Campos, M. (2019). Ketogenic diet: Is the ultimate low-carb diet good for you?. Available: Last accessed 2019-09-22.

[xi] Pecoits-Filho R. (2007). Dietary protein intake and kidney disease in Western diet. Contributions to Nephrology. 155, 102–112. (abstract)

[xii] Newman, T. (2019). Keto diet: New study unearths sex differences. Available: Last accessed 2019-09-22.

[xiii] Juanola-Falgarona, M et al. (2014). Effect of the glycemic index of the diet on weight loss, modulation of satiety, inflammation, and other metabolic risk factors: a randomized controlled trial. American Journal of Clinical Nutrition. 100 (1), 27-35. (abstract)

[xiv] Sutton, E et al. (2018). Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism. 27 (6), 1212-1221.

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