7 Keto Side Effects

The ketogenic diet—called the "keto" or just "keto"—is one of many weight-loss eating patterns. Though this way of eating may help you lose weight, some keto diet side effects and complications can include diarrhea, mineral deficiencies, or reduced athletic performance.

A person can experience these effects as the body achieves a state of ketosis by decreasing carbohydrate intake to 50 grams or less daily. In ketosis, the body has to burn fat rather than sugar for energy. Here's what you need to know.

Potential Negative Side Effects

Drastic changes in eating patterns can lead to side effects beyond weight changes. For people following the keto diet, doing it incorrectly or for too long may increase the risk of side effects like kidney stones or nutrient deficiencies.

1. Dehydration

This type of diet can cause individuals to have water loss before fat loss. As a result, one of the possible early side effects of ketogenic diets is dehydration.

Dehydration occurs when your body loses too much fluid. When you're dehydrated, you lose more fluid than you're taking in. Some symptoms of dehydration can include:

• Changes in urine, like dark-colored urine
• Dizziness
• Dry mouth
• Increased thirst
• Tiredness

2. Gastrointestinal Issues

Common side effects of a keto diet are gastrointestinal (GI) problems like constipation, diarrhea, nausea, or vomiting. Of those problems, diarrhea happens more frequently—potentially due to the body having difficulty absorbing the high-fat content of foods part of the diet.

3. Kidney Stones

The keto diet could lead to kidney stones, mineral-formed substances in your kidneys.

One review found that kidney stones are more likely to occur in people without kidney disease following keto because of the focus on animal-based and high-fat foods. For those with kidney disease, keto can lead to further long-term kidney damage, and worsen metabolic acidosis. The review also indicated that ketoacidosis may be responsible for kidney stone formation due to decreased citrate and pH levels and increased calcium levels in the urine.

4. Reduced Athletic Performance

Athletes may consider the ketogenic diet helpful for weight loss and improved sports performance. However, researchers found that participants performed worse on high-intensity cycling and running tasks after four days on a ketogenic diet than those who'd spent four days on a high-carb diet.

5. The "Keto Flu"

For some people, going on the keto diet can lead to the keto flu. It consists of the following symptoms:

• Constipation
• Dizziness
• Exercise tolerance difficulties
• Fatigue
• Headache
• Insomnia
• Nausea or vomiting

You may minimize the effects of keto flu by drinking plenty of water and increasing electrolyte intake. Other helpful actions include slowly decreasing your carb intake and easing your way into the diet.

6. Vitamin and Mineral Deficiencies

Many fruits and vegetables may be limited or eliminated to keep carb intake low on the keto diet. Doing so may lead to a lower intake of important nutrients such as:

• Calcium
• Fiber
• Iron
• Magnesium
• Potassium
• Various vitamins

Specifically, a person using the keto diet may also miss out on folate and thiamin as well as vitamins A, B6, B12, C, E, and K. These and other vitamins are essential for body functions and development related to bones, gums, metabolism, red blood cells, and more.

7. Weight Regain

Due to the keto diet's level of restriction for eating, people may regain any lost weight when they return to their initial eating patterns. This is in part because it's difficult to follow long-term and sustain.

Recommendations for the length of time to stay on the diet range from two to three weeks up to 12 months. If the keto diet is something you're interested in, talk with a dietitian for guidance.

Potential Benefits

While the keto diet has many less desirable side effects, you could experience beneficial side effects for your physical and mental health.

Appetite Control

The keto diet can be helpful for appetite regulation by affecting ghrelin. Ghrelin is the hormone that tells you you're hungry. There is an increase in ghrelin secretion when a person loses weight from dieting. However, this hormonal response becomes decreased during ketosis.

Blood-Related Changes

Researchers said that in the initial six to 12 months of the diet, individuals may experience blood pressure, blood sugar, and triglyceride decreases. They might also see an increase in good cholesterol, or high-density lipoprotein (HDL) cholesterol.

Emotional and Cognitive Changes

Research has shown the keto diet to be helpful for some mental health and cognitive conditions or symptoms. One review found that the diet was associated with symptom improvements concerning:

• Anxiety
• Auditory and visual hallucinations
• Cognition
• Communication skills
• Energy levels
• General mood

Though the review indicated positive results, the researchers said more extensive studies are needed to determine more about the benefits of the keto diet for mental health conditions.

Seizure Frequency Reduction

The keto diet does have some positive side effects beyond weight loss. Keto diets have been used for over 100 years for epilepsy treatment, and are effective in reducing seizure frequency in individuals with drug-resistant epilepsy and reducing weight.

Who Should Avoid the Keto Diet?

Individuals with the following conditions should avoid the keto diet:

• Eating disorders or a history of the disorders
• Fat metabolism disorders (e.g., disorders of fat storage)
• Gallbladder disease
• Liver failure or other liver conditions
• Pancreatitis
• Thyroid problems, like hypothyroidism

If you've been diagnosed with diabetes and prescribed insulin or hypoglycemic medications, talk with a healthcare provider prior to starting this diet. You might experience severe hypoglycemia without proper medication adjustments beforehand.

Is the Keto Diet Healthy?

Keto can be good for you. Though the diet emphasizes high-fat and low-carb foods, it allows for moderate-protein foods. Your body needs protein to help build body structures like bones, skin, and hormones.

Research has also shown the keto diet to be helpful for individuals with neurological disorders—like dementia or epilepsy—and overweight or obesity.

However, eating according to the keto diet can be bad for you due to its focus on high-fat content. Low-density lipoprotein (LDL) cholesterol levels increase with increased consumption of foods with saturated fats like beef, pork, cheese, and butter. Higher LDL cholesterol levels are linked to an increased likelihood of heart disease or strokes.

A Quick Review

Some keto side effects include dehydration, ketoacidosis, and the keto flu. The diet is not for everyone, such as those with kidney or liver problems. For those who can do keto, possible benefits beyond weight loss may be improvements in blood sugar, good cholesterol, or mood. Consider working with a registered dietitian to ensure you get adequate nutrients.