Keto Diet – Side Effects and Contraindications

Keto Diet – Side Effects and Contraindications post thumbnail image

Side effects of the keto diet

Is it bad to go on a ketogenic diet or a keto diet? No, getting a keto adaptation causes interesting benefits at the level of sports performance, but it is not magic, it is a process. During the first week or two on a ketogenic diet it is normal to suffer some side effects such as headache, constipation, fatigue, cramps and palpitations among others. Most of these side effects appear within the first week of starting a ketogenic diet and gradually disappear as you adjust to ketosis.

One of the causes of these side effects of the keto diet is dehydration. This can be mitigated with an increased intake of water and electrolytes. There is no single and universal recommendation on the volume of water we should ingest per day, as it depends on body weight, training, sweating, ambient temperature, humidity, etc. But, as a general recommendation, consuming between 2 and 4 liters of water a day and increasing the salt intake in meals to retain more fluid, we can reduce this effect.


Keto Flu

Keto Flu is not really the flu. It is not contagious. It occurs when fat burning increases and urine production increases temporarily.

The symptoms are: fatigue, headache, irritability, difficulty concentrating, dizziness, nausea, lack of motivation and cravings for sweets. These symptoms can disappear in less than half an hour just by drinking a good glass of water with a teaspoon of salt.

If it persists, you can increase your fat intake and, as a last resort if the symptoms are very bothersome, increase your carbohydrates a little so that the adaptation is slower and the results take longer to see. It is best to be patient.

Another way to reduce the mildness of side effects is to do a week or two of adaptation to ketosis where we would do a transition planning between what we consider a “normal” diet and a keto or ketogenic diet.

Dieta keto-Nutricional-dolor-de-cabeza


Halitosis or bad breath is not only a side effect of nutritional ketosis, it is an indicator that we are doing well, since this smell is produced by one of the ketone bodies: the ketone. Bad breath usually disappears after a few weeks in ketosis . If it does not disappear and it becomes a problem, the most indicated, apart from masking it with gum or mouth sprays, is to reduce the level of ketosis by slightly increasing the consumption of carbohydrates. For example, if with 20-30 g / day of carbohydrates it does not go away in a couple of weeks, it goes up to 50-60 g / day.

Physical performance and Keto Diet

During the first weeks of nutritional ketosis, physical performance can be severely affected. It is necessary to adapt our metabolism to the efficient use of fat and this requires weeks or months. Previous studies lasted between 1 and 2 weeks, insufficient time for adaptations to nutritional ketosis to be observed. For this reason, classic sports nutrition has rejected low and / or very low carbohydrate diets.

As we indicated at the beginning of the post, to avoid a great loss of performance it is important to place greater emphasis on hydration during the first phases.


Muscle mass and strength

Strength training depends mainly on phosphocreatine as an energy substrate, since they are high intensity efforts and very short in time. In keto diets or ketogenic diets, these deposits are not altered, so strength development is not affected.

Another case is that of muscle mass. In hypertrophy workouts, more repetitions are performed, using, in addition to phosphocreatine, muscle glycogen (glucose) stores as an energy substrate. The insulin that is released when ingesting carbohydrates has a certain anabolic effect (consumes energy), so when comparing groups with equal calories, those who carry out diets high in carbohydrates have greater muscle mass gain and those who follow a ketogenic diet, greater loss of body fat.

Contraindications Keto Diet


Ketoacidosis is a rare condition where ketone bodies are produced uncontrollably. It is really strange that it occurs in healthy people who are not receiving any type of drug treatment.

Type I diabetes

Ketone bodies are produced depending on the amount of insulin in the blood. If there is no insulin, they are produced at such a high rate that they do not have time to use them and they accumulate in the blood producing ketoacidosis. When following a ketogenic diet you will need a lower dose of insulin, but you will still need to inject it.

Type II diabetes

If you are receiving treatment for type II diabetes, you should consult your doctor about how to modify your treatment in order to follow a ketogenic diet without risk.


During lactation, around 30 g / day of carbohydrate is lost through milk. On certain occasions, a complete restriction of carbohydrates can lead to ketoacidosis, so if you want to follow a ketogenic diet during this period, it is recommended that it provide a moderate amount of carbohydrates, about 50 g / day. This can be easily achieved by adding 2-3 pieces of fruit daily.

Liver problems

Ketosis can be safe and even beneficial for some liver conditions, but if you have any, consult your doctor first before following a ketogenic diet.


Sometimes, at the beginning of nutritional ketosis, uric acid levels rise physiologically, this in people predisposed to gout attacks can increase the risk of having an attack, although it has been seen in studies that the antioxidant effect of ketone bodies, especially beta-hydroxybutyrate, prevents such attacks. So it’s not clear whether a ketogenic diet increases or decreases the risk of gout attacks.


These are just a few of the problems that can appear during nutritional ketosis. As you have seen, it is not recommended for everyone. Therefore, if you decide to start a ketogenic diet and you notice that something is wrong (unlikely but possible) do not hesitate to ask your GP.

Here are some recipes that can be used on a ketogenic diet, if we respect the quantities and proportions:

Grilled salmon with cauliflower, broccoli and steamed carrot

Salmon-a-la-plancha-con-coliflor,-brocoli-y-zanahoria-al-vapor- dieta keto-Nutricional-recetas


  • Salmon 120 g
  • Broccoli 80 g
  • Cauliflower 80 g
  • Carrot 60 g
  • Table salt 1 g
  • Olive oil 5 g
  • Black pepper 1 g


  1. Clean and chop the cauliflower, broccoli and carrot.
  2. In a steamer or Lekué steam the vegetables until they are soft.
  3. Meanwhile, cook the grilled salmon.
  4. Plate and season with olive oil, salt and black pepper.

Indicators for a portion

Kcal: 293
Proteins: 38% | Hydrates: 22% | Fat: 40%

Grilled pork loin with apple and onion

Lomo-de-cerdo-con-manzana-y-cebolla-a-la-plancha-dieta keto-Nutricional-recetas


  • Pork loin 100 g
  • Apple 80 g
  • Table salt 1 g
  • Black pepper 1 g
  • Olive oil 7 g
  • Red onion 50 g
  • Dried rosemary 1 g


  1. Wash and cut the apple into wedges, the onions into slices.
  2. Cook the onion in a griddle or pan with oil.
  3. When it is starting to brown add the apple wedges.
  4. Season the pork tenderloin and add it to another skillet for a quick heat.
  5. When you have the preparations ready, plate and serve.

Indicators for a portion

Kcal: 324
Proteins: 26% | Hydrates: 19% | Fat: 56%

Salmorejo with Serrano ham and hard-boiled egg



  • Salmorejo packaged 250 g
  • Serrano ham cubes 60 g
  • Cooked egg 60 g


  1. Serve the fresh salmorejo in a glass or cup.
  2. Add the serrano ham cubes to the bowl.
  3. Now chop the hard-boiled egg and add it too. Ready! Bon appetit 🙂
  4. Tip! If you want the ham to be crispy, cook it in the microwave on a piece of kitchen paper for 1 minute.

Indicators for a portion

Kcal: 426
Proteins: 28% | Hydrates: 17% | Fat: 54%

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