What is the keto diet?
The keto diet is a low-carb, high-fat diet popular for weight loss, but experts warn it might not have lasting results. So, is keto bad for you? Does it have side effects? Here’s what to know.
The keto diet, short for ketogenic diet, is a strict eating style, sometimes called a fad diet. The goal is to eat high-fat, moderate-protein, and low-carb meals so that your body uses ketone bodies instead of glucose as fuel.
Nutrients are often divided into percentages so that your diet includes mostly fat and protein, though ratios change:
- Fat: 55% to 60%
- Protein: 30% to 35%
- Carbohydrates: 5% to 10%
That works out to only about 20 to 50 grams of carbohydrates per day in a 2,000-calorie diet.
How does the keto diet work?
Normally, you get glucose, or sugar, from carbohydrates. Your blood glucose, or blood sugar, levels rise after eating carbs, causing insulin release in response. Insulin helps glucose get into your cells, where it’s used to make energy.
If you have lots of extra glucose, your liver stores it as a type of glucose called glycogen until those liver cells are full. Then, your body stores glucose as fat. When you stop eating carbs, your glucose levels fall, and your body breaks down these glycogen stores.
Once your glycogen is gone, insulin drops, and your body can’t keep up with the energy demands without incoming glucose, so it turns to fat. Fat breaks down into fatty acids, which convert to ketone bodies called beta-hydroxybutyrate and acetone and act as fuel for cells. This is called being in nutritional ketosis.
Ketone bodies are sometimes called a superfuel because they can make more energy than glucose, and your body uses them well. Your body will use ketones as fuel until you eat carbs again.
Benefits of the keto diet
Studies show that the keto diet helps protect the brain and can lower seizures in children, sometimes just as well as medication. It can produce metabolic changes in the short run and cause fast, intense weight loss in the first few weeks, though these results might not last.
Studies also show that the diet can improve insulin sensitivity, blood pressure, cholesterol, and blood fat levels. Early studies show that a keto diet might also help with type 2 diabetes, though more research is necessary. But the diet also has side effects.
Negative effects of the keto diet
While the keto diet has some benefits, there are drawbacks and risks. Overall, there isn’t enough research to recommend the keto diet long-term.
Hard to follow
Your body normally uses carbohydrates as fuel, and most people’s food patterns include about 50% carbohydrates. Banning a major food group in your diet is very restrictive and hard to follow long-term. It can also cause vitamin and mineral deficiencies and might lead to unhealthy eating habits like binge eating or overeating.
High in saturated fat
Fruits and vegetables are carbohydrates, which means you eat very little of these on a keto diet. Instead, you eat mostly meat, sausage, processed meat, fish, poultry, eggs, cheese, nuts, butter, seeds, oils, and some fibrous vegetables. While these can all be healthy foods, they’re high in saturated fats.
Saturated fats come mostly from animal foods, are solid at room temperature, and are linked to higher cholesterol levels and heart disease. Early studies suggest a keto diet can raise your cholesterol levels. In one study, 141 children followed a keto diet for six months. The keto diet led to significantly higher VLDL and LDL or bad cholesterol and decreases in good cholesterol.
But other studies showed the opposite. After 24 weeks of a ketogenic diet, patients with obesity had higher HDL or good cholesterol and lower total cholesterol. They also had significantly lower LDL cholesterol, blood fats, and blood sugar levels.
Still, experts recommend limiting your saturated fat intake to 5% or 6% of your diet. While healthy unsaturated fats are allowed on the diet, high amounts of saturated fats are often encouraged.
Causes short-term side effects
Extreme carbohydrate restriction can cause short-term side effects, commonly called the keto flu. These include symptoms like:
- Nausea
- Vomiting
- Dizziness
- Headache
- Tiredness
- Constipation
- Trouble sleeping
- Trouble exercising
While it’s called the keto flu, you don’t have a virus or an illness. It’s unclear why this happens, but symptoms can last a few days up to a few weeks. Drinking water and electrolytes can help ease some of these symptoms.
These symptoms might be unnecessary, though. Carbohydrates in healthy foods like whole grains, fruits, and vegetables aren’t bad. You can avoid these symptoms altogether by getting enough carbs from healthy sources.
Can cause kidney stones
Your kidneys help break down protein. A diet high in animal protein, like the keto diet, can lead to high uric acid levels and kidney stones. It can also increase your risk for gout, a condition where uric acid crystals build up in your joints and cause pain.
Can cause liver problems
If you have existing liver problems, the keto diet can make them worse. Your liver breaks down fat and converts it to energy and cholesterol. A high-fat diet like the keto diet can cause fat to build up in your liver and lead to fatty liver disease.
Animal studies suggest the keto diet can cause non-alcoholic fatty liver disease, or NAFLD, and raise liver enzyme levels. However, other studies suggest that the keto diet can improve NAFLD and lower liver fat content.
These are early animal or human studies that show early results, though. More research is needed to understand how or if the keto diet produces long-term results.
Is keto bad for you?
Experts generally don’t recommend the keto diet because it’s extreme and hard to follow. It may be beneficial for brain conditions like epilepsy and seizures that don’t respond to medications and might help you lose weight quickly. However, it’s not clear that results last.
The keto diet also might have harmful side effects, including nausea, brain fog, and more severe complications like kidney and liver problems. If you want to do the keto diet, experts suggest doing it for no more than 6 to 12 months and with regular monitoring. Talk to your doctor if you have an eating disorder, diabetes, or liver or kidney disease.
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Medically Reviewed on 2/13/2023
References
SOURCES:
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Experimental & Clinical Cardiology: "Long-term effects of a ketogenic diet in obese patients."
Frontiers in Nutrition: "Ketogenic Diets and Chronic Disease: Weighing the Benefits Against the Risks."
Frontiers in Physiology: "Emerging Role of Hepatic Ketogenesis in Fatty Liver Disease."
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Harvard T.H. Chan School of Public Health: "Carbohydrates," "Diet Review: Ketogenic Diet for Weight Loss."
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