The Keto Diet: Benefits, Risks, and What the Research Says

Jitka Burger
Jun 10, 2024
7 min read

The ketogenic diet has become one of the most talked-about dietary approaches in recent years. Praised for rapid weight loss and potential therapeutic effects, the diet has gained popularity far beyond its original medical use. While some individuals report positive results, the ketogenic diet also raises important questions regarding long-term safety, sustainability, and overall health outcomes.

Originally developed as a treatment for drug-resistant epilepsy in children, the ketogenic diet is a high-fat, very low-carbohydrate eating pattern designed to shift the body into a metabolic state called ketosis. Today, it is often promoted for weight loss, blood sugar control, athletic performance, and even disease prevention. However, the science surrounding the diet is complex, and the potential benefits should be weighed against possible risks.

What Is the Ketogenic Diet?

Under normal physiological conditions, glucose is the body’s primary fuel source. When carbohydrate intake is drastically reduced, the liver begins converting fats into ketones, which can serve as an alternative fuel source for the brain and body. This metabolic state is known as ketosis.

To achieve ketosis, carbohydrate intake is typically limited to approximately 20–50 grams per day, although the exact amount varies between individuals. For perspective, one cup of blueberries contains about 21 grams of carbohydrates, while one cup of raspberries contains about 15 grams.

Maintaining nutritional ketosis can be challenging. Some individuals monitor blood, breath, or urine ketone levels to confirm they remain in ketosis, since consuming too many carbohydrates — or in some cases too much protein — may prevent ketone production. Without monitoring, some people may simply be following a very high-fat diet without consistently reaching ketosis.

A typical ketogenic diet consists of approximately:

70% fat
20–25% protein
5–10% carbohydrate

Foods commonly emphasized on ketogenic diets include:

High-fat meats
Eggs
Cheese and other high-fat dairy products
Oils and butter
Avocados
Nuts and seeds
Coconut products

Low-carbohydrate vegetables such as leafy greens, broccoli, cauliflower, zucchini, and small amounts of berries are generally allowed.

Foods usually restricted include:

Bread and pasta
Rice and grains
Beans and lentils
Most fruit
Sugary foods and beverages
Starchy vegetables such as potatoes and corn
Alcoholic drinks

The health effects of a ketogenic diet may depend heavily on the quality of foods consumed. Diets centered around processed meats, butter, and saturated fats may affect health differently than versions emphasizing unsaturated fats, non-starchy vegetables, nuts, seeds, and minimally processed foods.

Keto diet infographic with pie chart and foods to eat or avoid: avocado, salmon, steak, eggs, cheese, greens, nuts, and no bread or sugar

Weight Loss: Looking Beyond the Scale

Many studies have shown that ketogenic diets can produce rapid short-term weight loss. Some of this early weight reduction is related to the loss of stored glycogen and associated water. Reduced appetite and spontaneous calorie reduction may also contribute.

However, weight loss alone does not necessarily indicate improved long-term health. Research comparing ketogenic diets with low-fat, plant-based diets has shown differing effects on body composition and metabolic health markers. Some studies suggest that while ketogenic diets may produce quick weight loss, low-fat plant-based diets may lead to greater reductions in body fat and improvements in insulin sensitivity and cardiovascular risk factors.

Depending on calorie intake, protein intake, and resistance training, lean body mass loss may also occur during weight reduction on ketogenic diets.

Potential Benefits

Research suggests that ketogenic diets may provide benefits in certain situations, including:

Treatment of drug-resistant epilepsy
Short-term weight loss
Improved blood sugar control in some individuals with type 2 diabetes
Reduced appetite and calorie intake

In people with type 2 diabetes, reducing carbohydrate intake often lowers blood sugar levels and may reduce the need for diabetes medications in the short term. However, lower blood sugar does not necessarily mean that the underlying insulin resistance has resolved. Some researchers believe that accumulation of fat within liver and muscle cells plays a major role in insulin resistance, and low-fat, plant-based dietary approaches have also been shown to improve insulin sensitivity in many individuals.

Scientists are also studying ketogenic diets for neurological conditions, including Alzheimer’s disease, Parkinson’s disease, and certain cancers, although much of this research remains preliminary.

Researchers have also explored ketogenic diets as a possible adjunct therapy for certain neurological conditions and cancers, including glioblastoma, an aggressive type of brain cancer. Because some tumor cells rely heavily on glucose for energy, scientists have investigated whether ketosis may influence tumor metabolism or improve responsiveness to standard treatment. While some early studies and reviews have reported promising findings, the current evidence remains limited, and more large-scale human trials are needed before firm conclusions can be drawn.

Possible Risks and Concerns

While some people tolerate ketogenic diets well, others may experience side effects or complications, particularly with long-term adherence.

Short-term side effects may include:

Constipation
Headaches
Fatigue
Dizziness
Nausea
Difficulty exercising at high intensity

These symptoms are sometimes referred to as the “keto flu” and may improve as the body adapts.

Long-term concerns may include:

Nutrient deficiencies
Low fiber intake
Elevated LDL cholesterol in some individuals
Kidney stone formation
Digestive issues
Potential impairment of endothelial (artery) function
Difficulty maintaining the diet long-term

Some animal and human studies have also raised concerns about insulin resistance, liver health, and cardiovascular risk markers associated with diets very high in saturated fat.

Some researchers have raised concerns about the long-term cardiovascular effects of ketogenic diets, particularly when they rely heavily on saturated fats and animal-based foods. Reported concerns include elevated LDL cholesterol levels, impaired endothelial function, and potential increases in cardiovascular risk markers in certain individuals.

Because ketogenic diets often restrict fruits, legumes, and whole grains, they may reduce intake of important nutrients, phytochemicals, and dietary fiber associated with long-term health and disease prevention.

Who Should Be Cautious?

The ketogenic diet may not be appropriate for everyone. Individuals with kidney disease, liver disease, pancreatitis, certain metabolic disorders, eating disorders, or other medical conditions should seek professional supervision before attempting a ketogenic diet.

Pregnant or breastfeeding women, children without a medical indication, and high-performing athletes may also need to exercise caution.

In some individuals, ketogenic diets can significantly raise LDL cholesterol levels, particularly when high amounts of saturated fat are consumed.

The Bigger Picture

Nutrition is rarely one-size-fits-all. While ketogenic diets may offer benefits for some individuals under specific circumstances, long-term health is likely influenced more by overall dietary quality, sustainability, and lifestyle habits than by ketosis alone.

A dietary pattern rich in minimally processed plant foods — including vegetables, fruits, legumes, whole grains, nuts, and seeds — has consistently been associated with lower rates of cardiovascular disease, type 2 diabetes, obesity, and other chronic illnesses.

Rather than focusing solely on macronutrient ratios, it may be more helpful to consider the broader picture: food quality, nutrient density, physical activity, sleep, stress management, and long-term sustainability.

Recent research comparing ketogenic and Mediterranean diets in individuals with prediabetes and type 2 diabetes found that both approaches improved blood sugar control. However, the ketogenic diet was associated with higher LDL cholesterol levels and was more difficult for some participants to maintain long-term, highlighting the importance of considering both effectiveness and sustainability when choosing a dietary pattern.

Before making major dietary changes, individuals should consider their health history, goals, preferences, and consult qualified healthcare professionals when appropriate.