Why the keto diet can be dangerous

The keto diet has risen in popularity over the last decade, being hailed not only as a method to lose weight but as a way to help manage diabetes and other medical concerns.³

But as time has passed, more research has been done on this high-fat, low-carb diet and how it impacts both physical and mental health. And after 10 years of testing, the scientific results have been mixed.

Diets, in general, can sometimes lead to disordered eating habits, and dieting more regularly has been linked to the earlier onset of certain disordered eating behaviors, including binge eating, weight cycling, and eating disorder pathology—or way of thinking—including an unhealthy focus on weight loss.¹

That's why it's important for anyone considering the keto diet to do their research and consult a trusted medical professional before following through. Making a thoughtful and informed decision can help keep keto-curious people safe.

What is the keto diet?

The keto diet is a style of eating that severely restricts the intake of carbohydrates while increasing fat intake, with the idea that this will encourage the body to burn fat for energy instead of carbs.

Though there are no "standard" recommendations on net carbs or fat, many resources suggest a daily macronutrient breakdown of:²

• 70-80% fat
• 5-10% carbohydrates
• 10-20% protein

Adhering to the keto diet food list means getting rid of most high-carb foods and sugary foods, such as:⁴

• Bread 
• Starchy vegetables, e.g., potatoes and sweet potatoes
• Sugary foods and beverages, e.g., candy, chocolate, soda
• Some fruits, such as bananas

Keto diet foods also often include many sources of healthy fats, such as the polyunsaturated fats and monounsaturated fats found in:⁴

• Olive oil
• Coconut oil
• Shellfish and other fatty fish
• Cheese
• Certain nuts and seeds, such as macadamia nuts
• Low-carb vegetables, like broccoli, brussels sprouts, and cauliflower

How does the keto diet work?

The idea behind the keto diet meal plan is to dwindle the supply of carb-based blood sugar, or glucose, which is often the first source the body metabolizes for energy. Once that happens, the body will turn to its fat supply instead, breaking down this energy source into a compound called ketones, in a process known as ketosis.²

The body typically takes 3-4 days to make this switch completely. In the meantime, it will raid the liver for stored glucose and even break down some muscle tissue to access the energy source.²

Eventually, insulin levels in the body will drop, and in response, the liver will start producing ketones, which can be used as an alternative form of energy.²

What are the dangers of the keto diet

Playing with the body's primary source of fuel can be a dangerous game.

Glucose is an important resource to the body, particularly the brain. The organ is the most energy-hungry part of the body, taking up to 20% of glucose-derived energy in the average person.⁵

Studies on replacing glucose with ketones to power the brain are mixed, with some pointing to a promise of reducing age-based diseases through the switch and others warning of a higher risk for impaired cognitive function when swapping glucose for ketones.^6,7

Too many ketones in the blood also leaves people susceptible to an issue called ketoacidosis, or a toxic amount of acid in the blood.² Keto diet proponents say those who follow the diet carefully should be able to avoid this situation, though how ketones accumulate in the blood also depends on several individualized factors, including body fat percentage and resting metabolic rate.²

Aside from the mixed findings of many scientific studies, there are other concerns about following the keto diet specifically or high-fat, low-carb diets in general.

Keto flu

While not an official medical term, the "keto flu" describes a list of common symptoms that occur in early ketosis or the period just after the body makes the switch to ketones for energy.⁸

Between two and seven days after starting the diet, a person could experience the keto flu. These symptoms can include:⁸

• Fogginess
• Fatigue
• Nausea
• Difficulty sleeping
• Irritability
• Headaches
• Constipation

While these symptoms are uncomfortable, they generally don't last too long. Rest and proper hydration are recommended.⁸

If symptoms persist for over a week, it may be time to seek further medical help.

Kidney stones

The newness of the keto diet means that while some risks—and benefits—have been identified, scientists may not be entirely sure why these things happen. This is the case for the diet's impact on the kidneys.

Studies have shown that those with a high-fat or low-carbohydrate intake may be at a higher risk of developing kidney stones. One analysis found that 5.9% of people following ketogenic diets developed kidney stones, including 5.8% of children and 7.1% of adults in the study.⁹

Digestive issues

Gastrointestinal issues are common for people on the keto diet, sometimes appearing as temporary side effects and sometimes lasting much longer. Some of the most common digestive problems related to keto diet foods include:⁸

• Constipation
• Cramping
• Abdominal pain
• Nausea or vomiting

Several colliding issues may cause digestive distress for people following keto, including changes to the gut biome, trouble eating enough fiber, and impacts on the liver and its production of bile.⁸

Compromised Bone Health

Although more research is needed, animal and human studies suggest that the keto diet may be linked to decreased bone strength.

One study in athletes found that bone modeling/remodeling markers were impaired after following a short-term, low-carb, high-fat diet similar to the keto diet. Markers only recovered after acute carbohydrate restoration.¹¹

The ketogenic diet has also been connected to a higher risk for osteoporosis.²

Long-Term Health Risks

Although people have been using the keto diet for more than 200 years, the overall risks and rewards are still unclear. While some studies have identified potential pitfalls or benefits, little is known about the long-term effects.

However, studies have found that low-carb diets, overall, can have many dangerous health impacts. Things that have been linked to long-term low-carb diets include:¹¹

• Heart arrhythmias
• Sudden death
• Kidney impairment
• Osteoporosis
• Increased risk for certain cancers 

High-fat diets, meanwhile, have generally been linked to increased risk of cardiovascular disease and impaired brain function.¹² 

Other options besides the keto diet

Eating keto diet foods has been proposed as a way to help manage concerning health conditions, including Type 2 diabetes and epilepsy.² While the research on those potential benefits is still being studied, people simply looking for a better way to manage their diet have other options.

Overall, eating a healthy, balanced diet has been shown time and again to be the best plan for overall health. And while it can be tricky to understand what a "balanced" diet entails or the best way to achieve one, some methods can help.

Mindful eating is one common strategy, particularly when managing portions, not fixating on food, and warding off eating patterns that can snowball into binge eating episodes. The technique focuses instead on the present moment—not thinking about food too much, but instead eating when you feel your body wants or needs food.¹³

It can also help change your focus from weight- or appearance-based goals to health-based goals. The Health at Every Size movement has a number of strategies for finding healthier ways to think about diet, movement, and body image.

Speaking to your primary care physician or a nutritionist about the best possible diet for you is another way to ensure you're getting enough of the foods, vitamins, and minerals you need for your specific body based on factors like your age, health status, and medical history.

Dieting is often presented in this world as a solution to the "problem" of being overweight. But sometimes, a changed perspective can be even more powerful than a changed body.

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