Does the Keto Diet Work? An RD Explains

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Does the Keto Diet Work?
A white plate with a steak and a few sprigs of rosemary

The Atkins low-carb diet craze of the early 1990s catapulted low-carbohydrate diets into the limelight. Low-carb diets focus on high protein and high-fat foods, and limit carbs more strictly than the typical healthy diet recommended by the Dietary Guidelines for Americans

Health-conscious people or those who want to lose weight often turn to low-carbohydrate diets for quick weight loss and the hope of weight maintenance. In the last 5–10 years, ketogenic, or “keto” diets have become the newest mainstream version of the low-carb diet.

Though there is some research that supports the keto diet’s effectiveness for weight loss and other health benefits, the keto diet may be unsustainable — and even unhealthy — to follow long term.  

The History of the Keto Diet

The “keto” diet is an abbreviation for ketogenic diet, whose purpose is to get into nutritional ketosis. When in ketosis, the body uses ketones — a product from breaking down fat — as its primary energy source instead of carbohydrates.

The ketogenic diet was designed by a physician at the Mayo Clinic in the 1920s to treat children with epilepsy. Though the mechanism for why the diet sometimes works to control epilepsy is not well understood, it’s still used today as an alternative option for children with epilepsy. The diet has also been used therapeutically for people with diabetes, obesity, cancer, and some neurological conditions. 

How Does the Keto Diet Compare to a Standard American Diet?

The Dietary Guidelines for Americans are the basis of nutrition recommendations in the United States, and provide guidance on what to eat and drink for a healthy diet. The Dietary Guidelines recommend that 45–65% of your daily calories come from carbohydrates. That leaves ~10–35% of calories from protein and 20–35% of calories from fat. The recommended healthy diet for adults should contain about 225–325 grams of carbohydrates per day in a 2,000-calorie diet based on these guidelines.

Authors of a 2021 ketogenic diet review article suggest that a diet with 50–150 grams of carbohydrates per day is the definition of a low-carbohydrate diet. While 50–150 grams of carbohydrates per day is much less than the recommended amount in the Dietary Guidelines, this level is likely not low enough to achieve ketosis. 

The ketogenic diet requires restricting carbohydrates to less than 50 grams per day and keeping protein intake to 1–1.5 grams per pound of body weight per day, which would be about 100–150 grams of protein per day for a 150-pound adult. The rest of your calories are supposed to come from fat sources.

Does the Keto Diet Work?

As noted above, the keto diet has plenty of evidence to support that it helps some children with epilepsy. 

Other potential health benefits include:

The potential benefits of the keto diet remain controversial, especially for maintaining any weight lost while following the diet. One review article of studies on the ketogenic diet suggests that most positive results are seen within the first 6–12 months of following the diet, but are generally not maintained after 12 months. Though weight loss occurs initially, the results are not statistically significant after about a year. Another review article included three studies of 24, 29, and 53 patients that did maintain statistically significant weight loss at the two year follow-up mark.

Many studies on the keto diet that demonstrate benefits include small groups of people and are conducted on a short-term basis. More long-term research is needed to determine the full possibilities of benefits from the keto diet.

Drawbacks of the Keto Diet

Though some people enjoy the short-term effects on their weight, the keto diet comes with some negative aspects. Some people may experience the “keto flu,” symptoms such as headache, fatigue, nausea, vomiting, and dizziness, for a few days up to a few weeks.

Carbs hold water (for every 1 gram of carb stored in the body, you retain 3 grams of water). Transitioning to low carb means you lose water. Insulin (a hormone that’s released to move sugar out of the blood stream) encourages the body to retain sodium, but low-carb diets typically lower insulin. What’s more, the loss of water and sodium can lead to the loss of potassium. 

Foods high in potassium, such as bananas, beans, and potatoes, tend to be cut from the keto diet. To combat keto flu symptoms, drink plenty of water, consider adding salty foods or salting your food or water (especially before you work out), and get potassium from lower-carb foods like spinach, broccoli, mushrooms, avocados, and salmon. 

Aside from short-term keto flu symptoms, the keto diet also:

  • May not be effective after about 12 months of usage, and may lead to increased cardiovascular risks. The diet increases low density lipoproteins and very low density lipoprotein levels in the blood, which have negative effects on heart health.

  • Can cause constipation since a low-carbohydrate diet is typically low in dietary fiber.

  • May increase the risk of kidney stones. Incidence of kidney stones while following the ketogenic diet is 3–10%.

  • May cause vitamin and mineral deficiencies if used long term, given that it eliminates many foods and food groups.

  • Can be hard to maintain. Any diet that requires limiting food groups can be difficult to follow for a long period of time. Carbohydrates are a large portion of a typical healthy diet, and the preferred fuel source for the human brain.

  • Requires counting and tracking, which can be tedious and may take away some of the joy and pleasure in eating.

  • Has social costs. Following a strict diet can make it hard to join people spontaneously for meals at restaurants or at their homes. You might miss out on social occasions that otherwise can fit into a healthy lifestyle, like birthday cake or a brunch with friends.

Registered Dietitian Tips

If you want to jump-start weight loss with the keto diet, make sure to read the following advice before slashing carbs.

Check with your healthcare provider. Though research on the ketogenic diet for various disease states is ongoing, the diet may be risky for people with chronic diseases, especially diabetes. If you have diabetes and take insulin or oral medications that control your blood sugar, take particular care to discuss any major diet changes with your healthcare team. The risk of hypoglycemia (when blood sugar drops dangerously low) is higher for diabetics who use medication.

Avoid strict diets if you have a history of disordered eating. Any diet that requires strict counting of macronutrients or calories could be harmful if you have issues with orthorexia (an obsession with healthful eating) or an eating disorder. If you’re not sure if you should follow a keto diet, please discuss it first with a therapist or healthcare provider who understands your history.

Consider using the keto diet short term. Unless instructed by a medical provider, following the ketogenic diet long term likely doesn't outweigh the benefits that may come from short-term weight loss. The keto diet may be useful to jump-start weight loss or see enough results to keep you motivated to create healthier habits. 

Liberalize the diet if it’s too restrictive.If you find yourself thinking about food all the time or the keto flu symptoms don’t resolve in a reasonable window of time, the amount of carbohydrates you’re eating might be unsustainable. Consider increasing the amount of carbohydrates you eat. You could keep some of the ideas from the diet in place — like limiting added sugars or replacing refined grain foods (white flour, white rice, processed foods) with recipes that use almond, cassava, or coconut flours — but eat “off limit” whole foods that provide vital nutrients (think apples, bananas, pears, sweet potatoes, peas, lentils, etc.).

Make the keto diet as nutrient-dense as possible. Though you need to limit carbs overall on the keto diet, focus on carbs that provide the most nutrition, such as non-starchy vegetables, berries, nuts, and seeds. Otherwise, focus on choosing lean proteins and plant-based fats such as avocados and olive oil.

Try convenience foods if you struggle to think of meal ideas. Many meal delivery services have keto-friendly options now. Check the freezer section of your grocery story, as many well-stocked grocery stores have frozen keto-friendly meals that you can buy. Two bits of advice: Ultra-processed foods, including keto options, can be OK in moderation but shouldn’t be the only source of food in your diet. Keto-friendly convenience foods tend to be more expensive than their non-keto counterparts. Your budget may require you to cook more at home, but that’s not a bad thing.

Add a multivitamin. Keto diets tend to have less overall diet variety, so it would be a good idea to take a daily multivitamin to ensure you meet all your micronutrient needs.

Minimize side effects. Drink plenty of water to prevent kidney stones. 

The Bottom Line

For most active people, a healthy diet consists mostly of lean proteins, healthy fats, whole grains, plenty of fruits and vegetables, lots of water, and some low-fat dairy or dairy substitutes. Although the keto diet may help you lose weight in the short term, it’s a hard diet to maintain long term. Research hasn’t shown additional benefits to following the keto diet long term for healthy people, so focus on improving your long-term diet quality in more sustainable ways.