The ketogenic diet won’t suit everyone. We’re all unique and have different responses to foods. Even if two people both respond well to a ketogenic diet, they may need to focus on different sources of fat. Here are some of the potential downsides to consider that are associated with going keto.
Please note: I am not a doctor, if you have any concerns about any of these symptoms or potential issues – seek medical advice from your GP.
Adaptation period and keto flu
Depending on your current health status and lifestyle, going keto may be a significant change for you. If you exercise regularly especially in low carb/fasted state and/or are metabolically flexible, adapting to nutritional ketosis will not be such a change.
If you are less metabolically flexible and used to relying on high carb meals, adapting to nutritional ketosis will be more of a change. During this adaptation period, of approximately two weeks, you may not feel yourself.
As you reduce your carb intake, glycogen stores (stores of carbs in the body) are depleted resulting in increased water excretion, as well as the electrolytes that go with it. Electrolytes (e.g. sodium, potassium) regulate fluid balance as well as having other important roles (e.g. nerve transmission, muscle contraction). The kidneys also excrete more sodium due to lowered insulin levels.
The net result is dehydration and electrolyte imbalance which may manifest in symptoms such as muscle cramps, fatigue, headaches, diarrhoea and constipation. The keto flu is a term used to describe the effects of this dehydration, loss of electrolytes and the body learning to utilise fat for fuel. Also, if your diet drastically changes from mainly processed foods to mainly whole foods, the body may excrete toxins.
Note: transitioning to going keto in a graduated way, with a diet which is energy and nutrient dense will improve this transition period! Make sure you keep really hydrated and replenish electrolytes.
Thyroid hormones and function are important throughout the body. As well as regulating basal metabolic rate (rate of energy production), they are involved in: central nervous system and bone development, heart and lung function, muscle contraction, the metabolism of fats, carbohydrates and proteins and fertility, ovulation and menstruation.
The production of thyroid hormones (thyroxine (T4) and triiodothyronine (T3)) involves the hypothalamus and pituitary gland and is therefore sensitive to other hormones present in the hypothalamus / pituitary gland – levels of thyroid hormones may influence the production of other hormones and vice versa.
Thyroid function is involved in carbohydrate metabolism and is influenced by carb intake. Going keto is associated with a reduction in T3 levels, which may be due to this. It may also be due to reduced calorie intake and weight loss, which are also associated with going keto.
An overactive stress response may also influence T3 levels via – suppression of the HPA axis (1) an inflammatory response and altering levels of other hormones which then affect active thyroid hormone levels (2).
If you are healthy, have no associated hypothyroid issues (energy levels are good and no difficulty losing weight) and feel well, then slightly lowered T3 levels from the ketogenic diet may not be problematic.
However, thyroid hormones are vital for health – stimulating bone turnover, influencing blood cholesterol levels (3) and influencing fertility, ovulation and menstruation (4) – so just be aware to keep yourself healthy!
Note: be mindful of how you feel and factors such as stress levels and calorie intake, which you may be more sensitive to whilst being on the ketogenic diet. Take into account who you are, your health status and lifestyle.
Blood cholesterol levels
Blood cholesterol levels vary in response to the ketogenic diet: some studies show no impact on cholesterol levels (5,6), whilst others show an increase in LDL-C (low density lipoprotein cholesterol) and HDL-C (high density lipoprotein cholesterol) levels (7).
There are so many factors that influence blood cholesterol levels – dietary factors such as, fat source and type, overall diet (protein type, fibre intake), as well as the genetic traits of an individual for metabolising fats/cholesterols.
Higher levels of LDL-C are a known risk factor for cardiovascular disease and therefore may be a concern associated with the ketogenic diet. Understanding the impact of cholesterol levels is more complex than simply LDL-C is bad and HDL-C is good, for example the size and number of LDL are important factors. There are also other risk factors that influence cardiovascular disease that need to be considered, such as levels of inflammation.
However, it is also advisable to take into account any genetic predispositions! If you have a genetic condition, such as hypercholesteremia or certain genes (for example the APOE4 allele) that mean that you’re a hyper responder to dietary cholesterol (8) then you need to take this into consideration when determining if a ketogenic diet is appropriate for you. Also consider the sources of fats you eat, such as monounsaturated fats versus saturated fats.
Other factors such as weight loss and low thyroid function may also influence LDL-C levels.
Note: take into consideration any genetic risk factors and the source of facts you eat as well as overall diet. Focus on eating fats that are within the foods themselves.
Low energy availability
If you’re lean/train regularly, approach the ketogenic diet with an awareness that the majority of advice is geared towards weight loss. Since many people end up cutting calories unintentionally (10) and have suppressed appetite (9) from the ketogenic diet, this may result in an unwanted energy deficit. Also, having lower body fat levels means that you have less available energy stores in the first place.
Energy availability is the energy left after the body has used utilised the energy required to stay alive and for any for exercise carried out. This available energy is required for the physiological processes that facilitate health in the long term, for instance, immune and menstrual function, bone growth, cardiovascular function etc.
Low energy availability (LEA) results in effects such as reduced metabolic rate, low energy levels, loss of bone density (osteopenia, osteoporosis), reduced sexual libido (loss of periods, reduced testosterone levels, reduced fertility) and increased likelihood to get ill repeatedly etc.
Although there are not direct studies on the ketogenic diet and low energy availability, athletes and weekend warriors are already at a much greater risk of LEA and studies on athletes on the ketogenic diet show weight loss despite being encouraged to eat adlibitum (10).
Note: plan to ensure that you meet your energy requirements if you train and be aware of your current body fat levels. Fat is not only necessary but has important roles – for the synthesis of hormones as well as insulation!
Restricted food choices may result in a less nutritious diet, impact social gatherings around food and lead to unhealthy psychological patterns. Obviously, this all completely depends on the individual, the diet and the approach.
To ensure a nutrient dense diet, it’s advisable to focus on whole foods that are unprocessed. From reducing carbohydrate intake you may reduce your intake of certain minerals and fibre and therefore educating yourself about the diet and having a plan to meet your requirements is advisable.
Be aware of how the diet may impact you socially and consider being flexible with the diet and using it as a tool rather than continually. Also consider how your thinking may become affected by restricting food choices. We eat several times a day and therefore behaviours around food can quickly become patterns that become entrenched with our daily lives.
Note: obviously if you have any history of an eating disorder, disordered eating, or obsessive routines and habits, be aware that going keto may potentially activate some of these historical patterns.
Sense of identity
Although merely my opinion, following diets or excluding certain foods have the potential to facilitate associating a sense of identity with them. The controversy between the dietary camps indicates this.
Note: be aware of why you are following the diet and create some head space between the food that you eat most of the time and who you are as an individual.
Final words for now…..
The isn’t much research yet about the long term effects of the ketogenic diet. Also most research is carried out individuals who have type 2 diabetes, or are obese and therefore we do not know what the impact is on relatively healthy / lean individuals is.
Take into consideration yourself! You, your genes, your health and lifestyle and be aware that most popular keto content out there is geared towards weight loss, which may not be beneficial to you.
Should I go keto as an athlete dives into the potential benefits for training in more detail and definitely check out What are the benefits of going keto to get the other side of going keto.
10 tips to starting a ketogenic the right way can also help you to begin you keto journey successfully!
What are your thoughts on the downsides of going keto? Leave any comments and thoughts below– I’m keen to know!
Thank you for reading!