Though it may seem newer to your newsfeed, the ketogenic diet has been around since the 1920s. The keto diet is all about cutting carbs and eating more fat, similar to the Atkins diet from the 1970s. The ketogenic or “keto” diet is a low-carbohydrate, fat-rich eating plan that has been used for centuries to treat specific medical conditions. In the 19th century, the ketogenic diet was commonly used to help control diabetes. In 1920 it was introduced as an effective treatment for epilepsy in children in whom medication was ineffective. However, this diet is gaining considerable attention as a potential weight-loss strategy due to the low-carb diet craze, which started in the 1970s with the Atkins diet (a very low-carbohydrate, high-protein diet, which was a commercial success and popularized low-carb diets to a new level).
What is the Keto Diet?
The ketogenic diet (or keto diet, for short) is a low carb, high fat diet that offers many health benefits. The keto diet reduces your total carb intake to less than 50 grams a day. This is the equivalent of a cup of white rice. Unlike other low-carb diets, which focus on protein, a keto plan centers on fat, which supplies as much as 90% of daily calories. It involves drastically reducing carbohydrate intake and replacing it with fat. This reduction in carbs puts your body into a metabolic state called ketosis. When this happens, your body becomes incredibly efficient at burning fat for energy. It also turns fat into ketones in the liver, which can supply energy for the brain (6). Ketogenic diets can cause significant reductions in blood sugar and insulin levels. This, along with the increased ketones, has some health benefits (6, 7, 8).
How the Keto Diet Works
The keto diet limits carbohydrates, forcing your body to burn fat for fuel instead. Roshini G. Merneedi, RD, a dietitian at Northwestern Medicine, explains that your body's primary energy source is glucose, which comes from the breakdown of carbohydrates. The premise of the ketogenic diet for weight loss is that if you deprive the body of glucose-the main source of energy for all cells in the body, which is obtained by eating carbohydrate foods-an alternative fuel called ketones is produced from stored fat (thus, the term “keto”-genic). When these stores are full, they are converted into fat. In this state, your body breaks down fats into molecules called ketones. Ketones serve as an alternative fuel source. The keto diet aims to force your body into using a different type of fuel. Burning fat seems like an ideal way to lose pounds.
Macronutrient Ratios
Generally, popular ketogenic resources suggest an average of 70-80% fat from total daily calories, 5-10% carbohydrate, and 10-20% protein. For a 2000-calorie diet, this translates to about 165 grams fat, 40 grams carbohydrate, and 75 grams protein. A ketogenic diet primarily consists of high fat intake, moderate protein consumption, and low carbohydrate intake. The macronutrient distribution typically ranges from approximately 55% to 60% fat, 30% to 35% protein, and 5% to 10% carbohydrates.
Types of Ketogenic Diets
There are several versions of the ketogenic diet, and what you eat depends on the type. They include:
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- Standard ketogenic diet (SKD): This is a very low carb, moderate protein and high fat diet. It typically contains 70% fat, 20% protein, and only 10% carbs (9).
- Cyclical ketogenic diet (CKD): This diet involves periods of higher carb refeeds, such as 5 ketogenic days followed by 2 high carb days.
- Targeted ketogenic diet (TKD): This diet allows you to add carbs around workouts.
- High protein ketogenic diet: This is similar to a standard ketogenic diet, but includes more protein. The ratio is often 60% fat, 35% protein, and 5% carbs.
However, only the standard and high protein ketogenic diets have been studied extensively. Cyclical or targeted ketogenic diets are more advanced methods and primarily used by bodybuilders or athletes.
Achieving Ketosis
Ketosis is a metabolic state in which your body uses fat for fuel instead of carbs. It occurs when you significantly reduce your consumption of carbohydrates, limiting your body’s supply of glucose (sugar), which is the main source of energy for the cells.
Following a ketogenic diet is the most effective way to enter ketosis. Generally, this involves limiting carb consumption to around 20 to 50 grams per day and filling up on fats, such as meat, fish, eggs, nuts, and healthy oils (6). It’s also important to moderate your protein consumption. This is because protein can be converted into glucose if consumed in high amounts, which may slow your transition into ketosis (10).
Practicing intermittent fasting could also help you enter ketosis faster. There are many different forms of intermittent fasting, but the most common method involves limiting food intake to around 8 hours per day and fasting for the remaining 16 hours (11).
Blood, urine, and breath tests are available, which can help determine whether you’ve entered ketosis by measuring the amount of ketones produced by your body. Certain symptoms may also indicate that you’ve entered ketosis, including increased thirst, dry mouth, frequent urination, and decreased hunger or appetite (12).
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Foods to Eat and Avoid on a Keto Diet
The keto diet excludes carb-rich foods like grains, beans, fruits and starchy vegetables.
Foods to Avoid
Here’s a list of foods that need to be reduced or eliminated on a ketogenic diet:
- Sugary foods: soda, fruit juice, smoothies, cake, ice cream, candy, etc.
- Grains or starches: wheat-based products, rice, pasta, cereal, etc.
- Fruit: all fruit, except small portions of berries or strawberries
- Beans or legumes: peas, kidney beans, lentils, chickpeas, etc.
- Root vegetables and tubers: potatoes, sweet potatoes, carrots, parsnips, etc.
- Low fat or diet products: low fat mayonnaise, salad dressings, and condiments
- Some condiments or sauces: barbecue sauce, honey mustard, teriyaki sauce, ketchup, etc.
- Unhealthy fats: processed vegetable oils, mayonnaise, etc.
- Alcohol: beer, wine, liquor, mixed drinks
- Sugar-free diet foods: sugar-free candies, syrups, puddings, sweeteners, desserts, etc.
Foods to Eat
You should base the majority of your meals around these foods:
- Meat: red meat, steak, ham, sausage, bacon, chicken, and turkey
- Fatty fish: salmon, trout, tuna, and mackerel
- Eggs: pastured or omega-3 whole eggs
- Butter and cream: grass-fed butter and heavy cream
- Cheese: unprocessed cheeses like cheddar, goat, cream, blue, or mozzarella
- Nuts and seeds: almonds, walnuts, flaxseeds, pumpkin seeds, chia seeds, etc.
- Healthy oils: extra virgin olive oil, and avocado oil
- Avocados: whole avocados or freshly made guacamole
- Low carb veggies: green veggies, tomatoes, onions, peppers, etc.
- Condiments: salt, pepper, herbs, and spices
It’s best to base your diet mostly on whole, single-ingredient foods.
Potential Benefits of the Keto Diet
Weight Loss
A ketogenic diet is an effective way to lose weight and lower risk factors for disease (1, 2, 3, 4, 5). In fact, research shows that the ketogenic diet may be as effective for weight loss as a low fat diet (13, 14, 15). What’s more, the diet is so filling that you can lose weight without counting calories or tracking your food intake (16). One review of 13 studies found that following a very low carb, ketogenic diet was slightly more effective for long-term weight loss than a low fat diet. People who followed the keto diet lost an average of 2 pounds (0.9 kg) more than the group that followed a low fat diet (13).
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Diabetes Management
The ketogenic diet can boost insulin sensitivity and cause fat loss, leading to significant health benefits for people with type 2 diabetes or prediabetes. Diabetes is characterized by changes in metabolism, high blood sugar, and impaired insulin function (20). One older study found that the ketogenic diet improved insulin sensitivity by a whopping 75% (25).
Other Health Benefits
Studies have now shown that the diet can have benefits for a wide variety of different health conditions:
- Heart disease: The ketogenic diet can help improve risk factors like body fat, HDL (good) cholesterol levels, blood pressure, and blood sugar (28, 29).
- Cancer: The diet is currently being explored as an additional treatment for cancer, because it may help slow tumor growth. (4, 30, 31).
- Alzheimer’s disease: The keto diet may help reduce symptoms of Alzheimer’s disease and slow its progression (5, 32, 33).
- Epilepsy: Research has shown that the ketogenic diet can cause significant reductions in seizures in epileptic children (3).
- Parkinson’s disease: Although more research is needed, one study found that the diet helped improve symptoms of Parkinson’s disease (34).
- Polycystic ovary syndrome: The ketogenic diet can help reduce insulin levels, which may play a key role in polycystic ovary syndrome (35, 36).
- Brain injuries: Some research suggests that the diet could improve outcomes of traumatic brain injuries (37).
However, keep in mind that research into many of these areas is far from conclusive.
Potential Risks and Side Effects
Following a very high-fat diet may be challenging to maintain. Some negative side effects of a long-term ketogenic diet have been suggested, including increased risk of kidney stones and osteoporosis, and increased blood levels of uric acid (a risk factor for gout). Possible nutrient deficiencies may arise if a variety of recommended foods on the ketogenic diet are not included.
Short-Term Side Effects
Although the ketogenic diet is usually safe for most healthy people, there may be some initial side effects while your body adapts. There’s some anecdotal evidence of these effects often referred to as the keto flu (38). Based on reports from some on the eating plan, it’s usually over within a few days. Reported keto flu symptoms include diarrhea, constipation, and vomiting (39). Other less common symptoms include:
- Poor energy and mental function
- Increased hunger
- Sleep issues
- Nausea
- Digestive discomfort
- Decreased exercise performance
To minimize this, you can try a regular low carb diet for the first few weeks. This may teach your body to burn more fat before you completely eliminate carbs.
Long-Term Risks
While the keto diet has its benefits, staying on it in the long term may have some negative effects, including risks of the following:
- Low protein in the blood
- Extra fat in the liver
- Kidney stones
- Micronutrient deficiencies
A type of medication called sodium-glucose cotransporter 2 (SGLT2) inhibitors for type 2 diabetes can increase the risk for diabetic ketoacidosis, a dangerous condition that increases blood acidity. Anyone taking this medication should avoid the keto diet (40, 41).
Dietitian Advice and Recommendations
Before starting a keto diet, it is recommended to consult with one’s physician and a dietitian to closely monitor any biochemical changes after starting the regimen, and to create a meal plan that is tailored to one’s existing health conditions and to prevent nutritional deficiencies or other health complications.
Sustainability and Balance
Baljash Singh Cheema, MD, a cardiologist at Northwestern Medicine Bluhm Cardiovascular Institute, says, “The ketogenic diet can be effective for weight loss when used in a short time period followed by the adoption of healthier eating habits. However, we know in studies of these types of diets that once people stop following that diet, they regain at least half of the weight that they lost".
Following a very high-fat diet may be challenging to maintain. Some negative side effects of a long-term ketogenic diet have been suggested, including increased risk of kidney stones and osteoporosis, and increased blood levels of uric acid (a risk factor for gout). Possible nutrient deficiencies may arise if a variety of recommended foods on the ketogenic diet are not included.
Intuitive Eating
When you micromanage your food intake by tracking how much you eat, it disconnects you from what your body is asking for. You start using outside numbers to determine what to eat instead of listening to your body. “Being intuitive and understanding what your body needs is essential for proper nourishment,” says Merneedi. Monitoring food so closely can lead to psychological distress, such as shame and binge eating.
Alternative Approaches
For long-term weight loss, Dr. Ring, Dr. Intermittent fasting is an approach that allows you to receive the benefits of ketosis while still eating a varied and balanced diet, says Dr. Ring. By cycling between periods of eating and fasting, your body enters “mild ketosis” during the fasting phase. “Unlike the keto diet, which requires strict food restrictions, intermittent fasting lets you enjoy a variety of nutrient-dense foods, such as fruits, vegetables, whole grains and legumes, during eating windows,” Dr. Ring explains.
Dr. Cheema advocates making small changes based on your health goals. “People tend to burn out on those big goals and challenges, and then they go back into their own habits,” he explains. “Just because you were super fit between the ages of 36 and 38 may not extend your healthy life. But if you make small changes consistently every day from ages 36 to 66, that probably will have a big impact. No one diet fits all, and what works for one person may not work for another.