The ketogenic diet, often simply called “keto,” has surged in popularity over recent years, lauded for its potential to deliver rapid weight loss, improved energy levels, and better blood sugar control. However, beneath the widespread enthusiasm lies a crucial question: who should not do keto? Despite its celebrated benefits for some, this highly restrictive diet is far from a one-size-fits-all solution and carries significant potential risks to health for specific individuals. It is imperative to fully understand these risks and consult with a healthcare professional before embarking on a ketogenic journey.
While the allure of a ketogenic diet is strong, promising transformative health outcomes, it’s critical to recognize that it’s not suitable for everyone. There are profound physiological and psychological implications associated with going keto, and being fully informed about these potential dangers is paramount before making any dietary changes.
This comprehensive article aims to shed light on some of the most significant potential dangers of a ketogenic diet. We will identify specific groups of people who should strictly avoid ketosis due to heightened health risks. These populations include, but are not limited to, pregnant and breastfeeding women, individuals with a history of eating disorders, those with thyroid conditions, people suffering from gallbladder disease, children and adolescents, and high-performance athletes. Our discussion draws from available research, though it’s important to note that definitive, large-scale studies on the long-term safety of the ketogenic diet for the general population are still limited.
What is a Ketogenic Diet?
At its core, a ketogenic diet is a dietary regimen designed to dramatically shift the body’s primary fuel source. The overarching goal is to consume a significantly high proportion of fat, a moderate amount of protein, and a very limited amount of carbohydrates. Typically, for most individuals following a standard keto diet, this translates to approximately 60-80% of daily calories from fat, around 15-25% from protein, and less than 10% from carbohydrates, often restricting carbohydrate intake to a mere 20-50 grams per day. This composition is drastically different from a typical Western diet, which is usually rich in carbohydrates.
The fundamental premise of a ketogenic diet is that by severely restricting carbohydrate intake, your body will deplete its glycogen stores and be forced to seek an alternative energy source. This leads to a metabolic state called ketosis, where the liver begins to produce ketone bodies from fat. These ketones then become the body’s primary fuel, providing energy to the brain and other organs in the absence of glucose from carbohydrates. Proponents suggest that this metabolic shift can lead to weight loss, more stable blood sugar levels, improved insulin sensitivity, and a reduction in inflammatory markers throughout the body.
While the body’s ability to utilize fat for fuel is a natural survival mechanism, the continuous and deliberate induction of ketosis through diet is an extreme form of low-carb eating. It requires meticulous attention to macronutrient ratios and often entails significant dietary restrictions, limiting a wide array of foods commonly consumed in a balanced diet. Understanding this fundamental shift is crucial before considering its adoption.
For more insights into different dietary approaches, you may want to explore my related article about What is an Ancestral Diet?
Who Should Avoid the Ketogenic Diet?
Before considering a ketogenic diet, it is absolutely essential to have a thorough discussion with a licensed healthcare provider, such as a doctor or a registered dietitian. They can provide personalized advice, assess your current health status, and help determine if a ketogenic diet is appropriate for your individual needs. They can also guide you in developing a safe and nutritionally adequate eating plan, regardless of the approach you choose.
Based on existing research, anecdotal evidence, and clinical consensus, certain groups of people are strongly advised to avoid a ketogenic diet due to potential health risks, severe adverse outcomes, or the exacerbation of pre-existing conditions. For these individuals, the restrictive nature and metabolic demands of keto can be detrimental rather than beneficial.
1. Individuals with a History of Eating Disorders
For people currently struggling with an eating disorder or those with a history of disordered eating patterns, highly restrictive diets like keto pose significant dangers. The strict rules, rigorous tracking of macronutrients, and elimination of entire food groups inherent in a ketogenic diet can act as powerful triggers, potentially reigniting unhealthy obsessions with food, weight, and body image. This can lead to a relapse into restrictive behaviors, binge-eating cycles, or other detrimental patterns that severely undermine mental and physical health.
Research increasingly suggests that individuals with a history of eating disorders or those in orthorexia recovery may benefit far more from a non-diet approach, which focuses on intuitive eating, body acceptance, and fostering a healthy relationship with food rather than imposing external rules. Therefore, unless explicitly prescribed and closely monitored by a specialized medical and psychological team, anyone with a history of disordered eating behavior should rigorously avoid this way of eating to protect their ongoing recovery and well-being.
Similarly, it’s worth noting that other popular diets, such as some forms of plant-based diets, can also present challenges if approached with an overly restrictive mindset.
2. Pregnant or Breastfeeding Women
Pregnancy and breastfeeding are periods of immense physiological demand, requiring increased caloric and nutrient intake to support both maternal health and fetal or infant development. A typical ketogenic diet, which often limits protein intake to around 15% of total calories, is generally not recommended for women who are pregnant or breastfeeding. Health guidelines suggest that pregnant women should aim for at least 20% of their calories from protein, with requirements potentially increasing to 25% during the third trimester when fetal growth accelerates dramatically. Insufficient protein can impair fetal development and compromise maternal health.
Furthermore, the significant carbohydrate restriction in a keto diet can signal a state of “food scarcity” to the body, potentially leading to increased stress hormone production. This is far from ideal when the body requires abundant and diverse nutrients to nourish a growing baby. The lack of variety in fruits, vegetables, and whole grains often seen in strict keto can also lead to deficiencies in critical micronutrients like folate, iron, and calcium, all vital for a healthy pregnancy.
Women who are trying to conceive should also exercise caution, as metabolic stress from extreme diets can sometimes affect fertility. Learn more about the best diet for fertility. You might also want to read this article on the dangers of intermittent fasting for women, as it shares similar themes of metabolic impact.
3. Those Experiencing Adrenal Dysfunction
While “adrenal fatigue” remains a controversial diagnosis not universally recognized by mainstream medicine, many individuals experience a cluster of symptoms attributed to adrenal dysfunction, often by alternative healthcare providers. This condition is typically characterized by the adrenal glands not producing hormones, particularly cortisol, in optimal levels or at the right times, leading to chronic fatigue, brain fog, and difficulty managing stress.
Although direct research on the impact of a ketogenic diet specifically on adrenal fatigue is scarce, existing studies suggest that low-carbohydrate diets can negatively affect cortisol levels. For someone whose adrenal system is already perceived to be under stress, the metabolic shift required by ketosis, which can be seen as a physiological stressor, could potentially exacerbate imbalances in cortisol production. This could worsen symptoms of fatigue and further compromise the body’s stress response mechanisms. More targeted research is needed, but caution is advised for individuals experiencing symptoms of adrenal dysfunction.
You may also find valuable insights in my article with resources if you feel tired all the time.
4. People with Hypothyroidism
The thyroid gland plays a pivotal role in regulating metabolism, and its proper function is highly dependent on various nutrients and hormonal balance. Crucially, insulin is required to facilitate the conversion of inactive thyroid hormone (T4) into its active form (T3). In a ketogenic diet, carbohydrate intake is drastically restricted, often leading to very low insulin levels. This can potentially impair the T4 to T3 conversion process, exacerbating hypothyroid symptoms.
Many individuals with hypothyroidism who have attempted a keto diet report a worsening of their symptoms, including increased fatigue, weight gain despite dietary changes, hair loss, and brain fog. At least one study has indicated that a ketogenic diet can induce thyroid malfunctions in some individuals, particularly by lowering T3 levels. For optimal thyroid function, a diet that provides adequate, quality carbohydrates may be more beneficial than one that severely restricts them.
See my related article on the worst foods for Hashimoto’s, which emphasizes a focus on whole, nutrient-dense foods rather than extreme restriction. In many cases, a grain-free diet, which is less restrictive than keto, might offer more relief and better support for thyroid health.
5. Individuals Without a Gallbladder or with Gallbladder Disease
The gallbladder’s primary function is to store and concentrate bile, a digestive fluid produced by the liver that is essential for breaking down and absorbing dietary fats. If you have undergone a cholecystectomy (gallbladder removal) or suffer from gallbladder disease, your body’s ability to process large amounts of fat is significantly compromised. Consequently, adopting a ketogenic diet, which mandates a very high fat intake, can be problematic.
The danger of going keto without a functional gallbladder or with gallbladder issues lies in the body’s potential inability to produce and deliver sufficient bile to efficiently emulsify and digest the high volume of fats. This can lead to a range of uncomfortable symptoms, including severe abdominal pain, nausea, bloating, diarrhea (especially after fatty meals), and steatorrhea (fatty stools). More seriously, it can result in malabsorption of fat-soluble vitamins (A, D, E, K) and essential fatty acids, potentially leading to nutrient deficiencies and overall malnutrition over time. The general dietary recommendations for these individuals typically lean towards a low-fat diet, making keto an ill-advised choice.
6. People with a History of Gut Dysbiosis
A healthy gut microbiome, characterized by a diverse and balanced population of beneficial bacteria, is fundamental to overall health, influencing everything from digestion and immunity to mood and metabolism. Emerging research indicates that a ketogenic diet has been shown to alter gut flora. For individuals with a history of gut or digestive issues, such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), or general gut dysbiosis, following a ketogenic diet requires extreme caution.
One of the primary concerns with a very low-carb keto diet is its potential to significantly reduce the diversity of the gut microbiota. Many carbohydrate-rich foods, particularly fruits, vegetables, legumes, and whole grains, are excellent sources of dietary fiber. This fiber acts as a prebiotic, feeding the beneficial bacteria in our intestines. When these carbohydrate sources are severely restricted on a keto diet, the gut microbes may be deprived of their essential fuel, leading to a reduction in their numbers and diversity. This imbalance can exacerbate existing digestive problems, impair immune function, and potentially contribute to chronic inflammation.
Prioritizing gut health often involves consuming a wide variety of plant-based foods rich in fiber. Learn more about natural probiotic food sources, the best gut healing foods, and approaches like how to eat a low-histamine diet, which often emphasize gut-supportive foods.
7. Children and Adolescents
Children and teenagers are in critical stages of growth and development, which necessitates a diverse and nutritionally adequate diet. Their bodies require a broad spectrum of macronutrients and micronutrients to support bone development, brain maturation, hormonal regulation, and overall physical growth. Unless specifically prescribed by a pediatric neurologist for conditions like refractory epilepsy (where it is strictly monitored), a ketogenic diet may cause significant nutritional deficiencies and impair healthy development in growing individuals.
The restrictive nature of keto can make it challenging to obtain sufficient amounts of vitamins, minerals, and other essential nutrients commonly found in fruits, starchy vegetables, and whole grains. For adolescent females, there’s a particular concern about potential disruptions to their menstrual cycles and a risk of delayed puberty on a very low-carb diet, both of which can have long-term implications for reproductive health. Read more about a keto diet for kids, including when it may be appropriate under strict medical guidance. You can also see my article on how to eat during your menstrual cycle for balanced nutritional advice.
Given the absence of definitive, large-scale research on the long-term safety and efficacy of ketogenic diets for healthy children and adolescents, it is paramount to consult directly with a pediatrician or registered dietitian before considering such a diet for a young person. Close monitoring is essential if any young individual is following this type of diet for medical reasons.
8. High-Performance Athletes
While some athletes explore the ketogenic diet for its potential to improve fat adaptation and endurance, it generally presents significant challenges for competitive or high-performance athletes, particularly those involved in high-intensity sports requiring explosive power or rapid bursts of energy. Higher activity levels inherently demand more calories and quick fuel, which traditionally come from readily available carbohydrate sources.
For most high-intensity activities, the body primarily relies on glycogen (stored carbohydrates) for fuel. While keto adaptation can enhance the body’s ability to burn fat, this metabolic shift may not adequately support peak performance in sports that heavily depend on anaerobic energy systems. Some research indicates that athletes adopting a ketogenic diet may experience issues with power output, sprint performance, and overall recovery. Conversely, a substantial body of research consistently demonstrates that higher-carbohydrate diets are generally best for athletes, supporting optimal glycogen stores, faster recovery, and sustained high-intensity efforts.
Individual responses can vary, and some endurance athletes might explore cyclical or targeted keto approaches, but for general high-performance sports, the limitations on readily available glucose often outweigh the benefits of fat adaptation.
Other At-Risk Groups
Beyond the categories detailed above, several other groups of people may not fare well on a ketogenic diet and should approach it with extreme caution, if at all. These include:
- Individuals with a history of kidney disease or kidney stones: The increased protein load associated with some interpretations of keto, combined with potential electrolyte imbalances, can put additional stress on compromised kidneys and potentially worsen kidney stone formation.
- People with liver disease: The liver plays a crucial role in fat metabolism and ketone production. An already compromised liver may struggle to handle the high-fat demands of a ketogenic diet, potentially leading to further liver damage or dysfunction.
- Individuals with Type 1 Diabetes: This is a critical group for whom a ketogenic diet is highly dangerous without strict medical supervision. The risk of developing diabetic ketoacidosis (DKA), a life-threatening condition where the body produces dangerously high levels of ketones, is significantly elevated. Nutritional ketosis should never be confused with DKA.
- Those on certain medications: A ketogenic diet can interact with various medications, particularly those for blood pressure, blood sugar, or thyroid conditions, potentially altering their efficacy or leading to adverse reactions.
Given the complex metabolic changes involved, there may be other underlying health conditions or individual physiological sensitivities that render a high-fat, low-carb diet unsuitable. Always prioritize a comprehensive medical evaluation.
What Does the Science Say About Keto?
It is important to acknowledge that while the ketogenic diet poses risks for certain populations, it also has well-established therapeutic applications and has shown benefits for specific groups of people, particularly when medically supervised. Traditionally, the ketogenic diet has been a cornerstone in the treatment of epilepsy, effectively helping to control seizures in both children and adults who haven’t responded to conventional medications. In these cases, the diet is meticulously calculated, implemented, and monitored by a specialized medical team.
Furthermore, individuals with Type 2 diabetes have shown significant improvements in various biomarkers when placed on a carefully managed ketogenic diet. Studies indicate that they may experience reduced insulin resistance (leading to improved insulin sensitivity), better control over blood sugar levels, and significant weight loss. For example, one study demonstrated that adults with Type II diabetes who followed a ketogenic diet for 12 months not only lost more weight but were also more likely to reduce or eliminate their need for diabetes medications compared to a control group on a moderate-carbohydrate diet.
However, it is crucial to differentiate between these medically supervised, targeted applications and the general adoption of keto for weight loss or wellness by the broader public. While the diet can be effective for weight loss, particularly in the short term, many individuals can achieve similar results by simply consuming fewer refined carbohydrates and focusing on whole, unprocessed foods, without needing to enter a state of deep ketosis. The bottom line remains that there is no single “right” diet for everyone. What proves beneficial for one individual’s specific health condition or metabolic profile may be entirely unsuitable, or even harmful, for another. Understanding your unique body and consulting with healthcare professionals is key to navigating the diverse landscape of dietary approaches.
Making Informed Dietary Decisions
Given the detailed considerations discussed, if you fall into one of the categories of people who may not benefit from – or could even be harmed by – a ketogenic diet, it is genuinely wise to think twice before adopting this dietary lifestyle. The pervasive popularity of the ketogenic diet in mainstream media and social circles does not equate to its universal applicability or safety for every individual. Trends come and go, but your long-term health and well-being should always be the priority.
Instead of blindly following popular trends, we encourage a personalized approach to nutrition. Listen to your body, observe how different foods and eating patterns affect you, and prioritize a balanced diet rich in whole, unprocessed foods. Most importantly, engage in an open and honest dialogue with a qualified healthcare provider or a registered dietitian. They can offer guidance tailored to your unique health history, current conditions, and lifestyle goals, helping you choose a sustainable and truly beneficial way of eating that supports your optimal health without unnecessary risks.
You might also be interested in this article where I explain the differences between paleo, keto, vegan, clean eating, and Whole30 diets, offering a broader perspective on various dietary philosophies. Additionally, you may want to check out my article on the dangers of intermittent fasting for women, which explores another popular, yet potentially risky, dietary approach.
Frequently Asked Questions About the Keto Diet
Q: Is the ketogenic diet safe for long-term use?
A: Currently, there isn’t enough extensive, long-term research to definitively confirm the safety and effectiveness of the ketogenic diet for the general population over many years. Most studies are short to medium term. Concerns exist regarding potential nutrient deficiencies, impacts on gut health, and possible long-term effects on organ function, particularly for the kidneys and liver, when not medically supervised.
Q: What are the common side effects of starting a keto diet?
A: Many individuals experience what is commonly known as the “keto flu” during the initial adaptation phase. Symptoms can include headaches, fatigue, brain fog, nausea, irritability, dizziness, and difficulty sleeping. These symptoms typically arise as the body transitions from burning glucose to burning fat for fuel and are often linked to electrolyte imbalances. While these usually subside within a few days to weeks, they can be quite unpleasant.
Q: Can I achieve weight loss without going full keto?
A: Absolutely. Many effective and sustainable weight loss strategies exist that do not require the extreme restrictions of a ketogenic diet. These include reducing intake of refined carbohydrates and sugars, increasing consumption of whole, unprocessed foods, focusing on portion control, and incorporating regular physical activity. A moderate low-carb diet or a balanced, whole-foods approach can lead to significant and lasting weight loss without the potential risks associated with deep ketosis.
Q: How do I know if I’m in ketosis?
A: Ketosis can be objectively measured using urine strips, breath ketone meters, or blood ketone meters (which are generally the most accurate). Subjective signs can also indicate ketosis, such as reduced appetite, increased energy and mental clarity (after the initial adaptation phase), and sometimes a distinct metallic or fruity odor in the breath. However, simply being in ketosis does not automatically guarantee health benefits, nor does it mean the diet is right for you.
Q: What if I’m interested in trying a low-carb approach but not strict keto?
A: A modified low-carb diet, often referred to as a “liberal low-carb” or “primal” approach, can be an excellent option for many people. This typically involves reducing sugars, refined grains, and highly processed foods, while still allowing for a wider variety of nutrient-dense fruits, vegetables, and legumes than strict keto. This approach can offer many of the benefits, such as improved blood sugar control and weight management, with fewer restrictions and potentially a better nutrient profile. Always discuss any dietary changes with a qualified healthcare professional.
Further Reading and Resources
- 7 Keto Risks to Keep in Mind
- Ketogenic diet: What are the risks?
- Should you try the keto diet?
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About the Author: Carrie Forrest has a master’s degree in public health with a specialty in nutrition and is a certified holistic nutritionist. She is a top wellness and food blogger with over 5 million annual visitors to her site. Carrie has an incredible story of recovery from chronic illness and is passionate about helping other women transform their health. Send her a message through her contact form.
Note: This post is for informational purposes only and is not intended as medical advice. Please consult your healthcare provider for recommendations related to your individual situation.