Keto diets have become very popular for weight loss in recent years. However, there are potential health consequences that you should be aware of before giving into this fad.
What is the keto diet?
The keto diet is touted as a quick and effective solution to weight-loss. However, it was originally used in a medical context for paediatric patients. In fact, the keto diet was and still is utilised to help decrease the recurrence of epileptic seizures in children. As for its effects on weight loss, numerous studies have shown short-term results. Nonetheless there is still a lot of uncertainty regarding its effectiveness and safety in the longer term.
It’s easy to get lost in the world of weight-loss fad diets, each one promising quick fixes and overnight solutions. From the Atkins diet to the Paleo diet, these low-carb, high-fat and high-protein diets are often called “keto” diets. However, a ketogenic diet in the medical sense is not just any low-carb diet. Indeed, whilst most low-carb diets focus on high protein intakes, a true keto diet is centred around fat, which can provide up to 90% of daily energy intake.
Ketone bodies
In essence, the keto diet makes your body use a fuel that is different to its default choice. In fact, instead of using carbohydrates (glucose) for energy which come from fruits, vegetables, grains and legumes, the keto diet uses ketone bodies. Our liver produces these ketone bodies using the fat we have stored in our body.
One may think that burning our fat stores is a great way to lose weight. However, the liver requires very specific conditions to produce ketone bodies. Firstly, it requires an extremely low carbohydrate consumption, less than 20 to 50 grams per day. For reference, a medium apple can contain up to 25 grams of carbohydrates. Furthermore, your body takes a couple of days to reach a stage of ketosis where your body begins to use fat as fuel instead of sugar. Finally, consuming too much protein can interfere with ketosis.
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“The keto flu encompasses symptoms including fatigue, irritability, nausea, brain fog, constipation and difficulty sleeping.”
Permitted foods
The keto diet has very high fat requirements, and typically fat is eaten at each meal. Some healthy unsaturated fats are allowed on the diet, such as nuts, seeds, olive oil and avocados. However, saturated fats are encouraged in large amounts. We will discuss later why this may be problematic. Furthermore, protein is included in the keto diet. However, there is no true distinction between lean proteins and protein foods that are rich in saturated fats such as bacon and pork. Again, this may be problematic from a health perspective.
As for fruit and vegetable intake, by nature these foods are typically high in carbohydrates. Therefore most fruits are restricted, but some varieties such as berries are permitted in small amounts due to their lower carbohydrate content compared to other fruits. Vegetables are also typically high in carbohydrates, therefore they are restricted to the lowest carb varieties such as leafy greens, broccoli, brussels sprouts, cauliflower, cucumber, celery, onions and garlic.(1)
Let’s discuss 10 reasons why a keto diet may not be the healthiest choice for you.
1. Potential nutrient deficiencies
There is a reason why as dietitians, we nag about the importance of including a wide variety of fruits and vegetables in your diet. Not only do they taste amazing, but they provide your body with an array of beneficial vitamins and minerals.
Moreover, when we talk about “eating the rainbow” (i.e., eating multiple colours of fruits and vegetables), this is because each colour represents a different nutrient. So, the more variety you eat, the more likely you are to meet all your nutritional requirements. However, what happens when we cut out a large proportion of such foods from our diet, as occurs with the keto diet? You may be at risk of micronutrient deficiencies. Namely, vitamin C, B vitamins, selenium, magnesium, and phosphorus are just some of the nutrients that are commonly found in fruits and vegetables.
So, if you do choose to follow a keto diet, it’s important to make sure that you are meeting all your nutrient requirements.
2. Liver issues
Keto diets are typically much higher in fat compared to “regular” eating patterns. Moreover, the liver is our body’s main organ which metabolises fat. For those with pre-existing liver conditions such as non-alcoholic fatty liver disease (NAFLD), a high-fat diet such as the keto diet may worsen clinical outcomes.
3. Kidney issues
Our kidneys help to metabolise the protein we consume through our diet. In the UK, the Reference Nutrient Intake (RNI) for protein for adults is 0.75g protein per kg body weight per day; this equates to 56g/day and 45g/day for men and women of average body weights (75 and 60kg respectively).
However, keto diets include much higher quantities of protein per person per day. Subsequently, this may overload the kidneys that need to work extra hard to metabolise the additional macronutrients.
4. Constipation
Keto diets are typically low in fibre-rich foods. These include fruits, vegetables, grains, and legumes. In fact, given that these foods are high in carbohydrates, keto diets exclude them from the list of “permitted foods”. However, fibre is an essential element for bowel regularity, along with hydration and physical activity. Indeed, these are the three pillars for regular bowel movements in otherwise healthy people. People on keto diets may find that they need a fibre supplement to avoid constipation.
5. Brain fog and mood imbalances
The primary form of fuel for our brain is sugar which we can obtain from eating healthy carbohydrates. However, in the absence of sugar, our body turns to fat as the primary source of fuel. Research has shown that this can lead people to feel confused and irritable. In fact, this side effect is popularly referred to as “keto flu”. Whilst the term is not scientifically verified nor recognised by medicine, many people on the keto diet report negative symptoms in the initial stage of dieting. The keto flu encompasses symptoms including fatigue, irritability, nausea, brain fog, constipation and difficulty sleeping. These symptoms usually appear between two days and one week after starting a keto diet.(2)
6. High saturated fat intake
One of the typical characteristics of a keto diet is that it is high in fat, and typically saturated fat. Given that there is virtually no limit on how much fat you can consume on a keto diet, many people end up eating large amounts of saturated fat. It is well documented that saturated fat intake is one of the leading causes of high cholesterol and subsequently, cardiovascular disease.
According to the British Nutrition Foundation, our saturated fat intake should not exceed 11% of total energy intake from food, which is roughly 30g per day for men and 20g per day for women.
Moreover, keto diets are linked to an increase in “bad” LDL cholesterol, a leading risk factor for heart disease.(3)
7. Social isolation
It’s safe to say that compared to other diets and eating patterns, the keto diet is relatively restrictive in terms of which foods can and can’t be eaten. For example, the Mediterranean diet doesn’t exclude any food groups and encourages moderation as opposed to avoidance across most foods. By nature, the keto diet is high-fat and low carb. However, in today’s western society, it would be difficult to find a social situation revolving around food in which there are virtually no carbohydrates in sight.
Take for example a birthday party where they serve cake, a pizza night with friends, an in-flight aeroplane meal, a dinner at your in-laws, the list is endless. Of course, this is not to say that pizza and cake should feature at every meal. But thinking of them as “bad” foods that we need to completely abolish from our diets can do more harm than good. Following a restrictive diet can keep us from attending social gatherings which we could have otherwise happily joined.
8. Fatigue
The keto diet can leave you feeling tired and fatigued. As previously explained, this can be due to the “keto flu” which occurs when your body is adjusting to lower intakes of carbohydrates. In addition, it is common to have cravings for carbohydrates, which will leave you feeling lethargic and low in energy. Our bodies default to using carbs as fuel, so when we remove that source of fuel, our body fights back.(2)
9. Eating disorders
Restricting entire food groups, unless it’s due to an allergy, intolerance, or other medical reason, is rarely a good idea. In fact, most dietitians will tell you that the healthiest diets encourage everything in moderation. Furthermore, attaching moral value to foods as “good” or “bad” can be harmful. The keto diet severely restricts carbohydrates which automatically removes a great deal of healthy foods from the diet.
The media has largely contributed to the popularity of fad diets, adding pressure on individuals to look a certain way. This societal pressure can have cascading effects leading to self-esteem issues and ultimately eating disorders. In fact, studies have shown that in the long-term, fad diets are unsustainable and can negatively impact health, both physical and mental. The research suggests that prior to embarking on a fad diet, people should consult with a healthcare professional to understand whether a specific diet is suitable for them.(4)
10. Gut flora
The human microbiota is made up of trillions of cells and thousands of bacterial species. It is influenced by our environment as well as our diet. In fact, the food we eat can significantly alter the bacteria in our gut. For example, research has shown that the typical Western diet which is high in fat and sugar and low in fibre reduces our body’s production of short chain fatty acids (SCFAs). In turn, this leads to the production of detrimental compounds in our gut which leads to the spread of bacteria associated with chronic inflammation. Moreover, an adequate intake of pre and probiotics is essential for a healthy gut. However, both pre and probiotic intake is significantly reduced in ketogenic diets.(5)
In addition, there is evidence to suggest that the type of fats we consume can impact our gut microbiome. In fact, diets that are high in polyunsaturated fats and plant-based protein ensure healthy gut function.(6)
Needless to say that most keto diets are neither high in plant-based protein nor are they high in healthy polyunsaturated fats. In fact, a group of researchers has suggested that in order to preserve gut health on a ketogenic diet, people should follow a series of practical recommendations. These include reducing animal protein intake, consuming fermented foods, adding unsaturated fats to the diet and including prebiotics and probiotics if required.(7)
Putting things into perspective
The keto diet is undoubtedly one of the more popular diets of recent years, and not only amongst those who are overweight or obese. In fact, many people are choosing to follow the keto diet even if they are not medically considered overweight or obese. Therefore, experts are beginning to wonder what the long-term consequences could be for a large proportion of individuals following a diet without a medical justification. In fact, there are no long-term reliable studies to support the safety of a life-long keto diet. In contrast, there is substantial evidence to show that largely plant-based diets reduce the risk of cancer and cardiovascular disease, all while increasing longevity.(3)
