Ketogenic Diet Review

Does it Work?

The scientific evidence for the Keto Diet is weak. While there are clinical trials demonstrating its effectiveness in managing blood sugar, and short term weight loss, there have been no long term studies on weight loss. Additionally, there is no evidence to supporting its long-term effectiveness in reducing the risk of heart disease, heart attacks, strokes, or other health problems.

Carnivore Review

Overview of the Ketogenic Diet

The ketogenic diet, originally developed in the 1920s, was initially used to treat severe epilepsy in infants and children under medical supervision. But today, this low-carbohydrate tool has become a mainstream method for weight loss and reduction of cardiometabolic risk factors. Its primary aim is to lower elevated blood sugar levels that may result in several health problems.

The keto diet's core principle is to maintain very low carb intake while consuming high amounts of fat. When you follow this diet for a week, your body is compelled to burn fat instead of glucose (sugar) for fuel, resulting in a state known as ketosis. The liver produces ketone bodies (ketones) by breaking down fats, which then become an alternative fuel for the brain, crossing the blood-brain barrier.

The ketogenic diet has grown in popularity as a weight-loss tool in recent years. Unlike other diets, it does not require you to count calories. Instead, it encourages you to consume high-fat foods like butter, cheese, and meats while avoiding carbohydrates. While it may be effective for weight loss and reducing blood sugar levels, it's crucial to follow the diet under the supervision of a medical professional, especially for people with pre-existing medical conditions.


The ketogenic diet is a low-carbohydrate, high-fat diet that puts the body in a state of ketosis, where it burns fat for fuel instead of glucose. It has been used for the management of blood sugar and as a tool for short-term weight loss, but its long-term effectiveness and safety are not well understood.

The Keto Diet Approach

The ketogenic diet is a low-carbohydrate, high-fat diet that requires a drastic reduction in carbohydrate intake and an increase in fat consumption. The diet typically limits carbohydrate intake to 20-50 grams per day and encourages the consumption of high-fat foods like butter, cheese, meats, nuts, and avocados. Foods like bread, pasta, grains, and sugary foods are often limited or avoided altogether.

The goal of the ketogenic diet is to put the body into a state of ketosis, where it burns fat for fuel instead of glucose. This occurs when the body's glycogen stores are depleted, and the liver starts breaking down fats into ketones, which are then used as fuel for the brain and body. The state of ketosis is achieved within a few days to a week of starting the diet.

Foods Allowed and Restrictions

The Atkins diet allows a range of foods, with specific allowances and restrictions depending on the phase.

Allowed Foods

  • Meat
  • Poultry
  • Fish
  • Seafood
  • Eggs
  • Full-fat dairy
  • Nuts
  • Seeds
  • Nut butter
  • Avocados
  • Olive oil and other oils
  • Non-starchy vegetables
  • Herbs and spices
  • Vinegar
  • Lemon juice
  • Water
  • Unsweetened coffee and green tea

Foods to Avoid

  • All grains and grain products
  • Starchy vegetables
  • Fruit
  • Sweetened beverages
  • Certain alcoholic beverages (beer and sugary mixed drinks)
  • High-carb condiments (ketchup, barbecue sauce, dipping sauces, and most salad dressings)
  • Fast foods
  • Processed meats such as hot dogs and deli meats
  • Foods with artificial sweeteners

Ketogenic Diet Risks

While the ketogenic diet may be effective for short-term weight loss and blood sugar management, there are potential risks associated with the diet that should be considered. Here are some specific risks based on the scientific literature:

  1. Nutrient deficiencies: Because the ketogenic diet restricts certain food groups, such as fruits and starchy vegetables, there is a risk of nutrient deficiencies, particularly in vitamins and minerals like vitamin C, folate, and potassium.
  2. Increased risk of heart disease: While the ketogenic diet may increase levels of protective HDL cholesterol in some people, it may also increase levels of "bad" LDL cholesterol in others. Some studies suggest that the diet may increase the risk of heart disease, particularly in people with pre-existing heart conditions.
  3. Kidney stones: The high-fat nature of the ketogenic diet may increase the risk of developing kidney stones, particularly in people who have a history of kidney stones.
  4. Gastrointestinal issues: The low-fiber nature of the ketogenic diet may lead to constipation and other gastrointestinal issues in some people.
  5. Disordered eating: The strict restrictions of the ketogenic diet may contribute to disordered eating patterns, particularly in people with a history of eating disorders.

It is important to note that while these risks have been identified in the scientific literature, they may not apply to everyone who follows the ketogenic diet.

Individuals with pre-existing health conditions, such as high blood pressure, high cholesterol, or a history of stroke or cardiovascular disease, should avoid the diet since the high intake of protein and fat can worsen these conditions.

The carnivore diet is high in saturated fats, which can elevate LDL or bad cholesterol levels and put individuals at risk of heart disease. Moreover, processed meats such as bacon and certain lunch meats are high in sodium and have been linked to certain types of cancer. A diet high in sodium can also cause kidney problems and high blood pressure. It is crucial to consult a healthcare professional before attempting any restrictive dietary regimen like the carnivore diet, as it may pose severe risks to your health.

Not All Carbs are Bad

Not all carbohydrates are created equal, and some are even beneficial for the body. In their natural form, carbohydrates provide essential fuel for the body and are rich in fiber, vitamins, and minerals that are vital for good health. The best types of carbohydrates are unprocessed and unrefined, such as fruits like apples, pineapple, and strawberries, and vegetables like carrots, sweet potatoes, and beets. Whole grains, like quinoa and whole wheat bread, are also great sources of healthy carbohydrates.

However, simple carbohydrates, such as sugary candies, cakes, and pies, should be avoided. These types of carbs are often high in preservatives, white sugar, and flour, which can lead to inflammation and weight gain, especially around the middle. Simple carbs can also contribute to many health conditions, including type 2 diabetes, obesity, and high blood pressure. While cutting out simple carbs can improve glucose control and lead to weight loss, eliminating all carbs is unnecessary and may even be harmful.

In fact, completely omitting carbohydrates from the diet can have negative effects on the body. It is essential to differentiate between good and bad carbohydrates and to incorporate healthy carbohydrates into the diet for optimal health.

The Latest Research

Heart Disease

In a 2017 study published in the journal Nutrients, researchers found that the keto diet produced positive effects on cardiovascular risk factors, including obesity, Type 2 diabetes, and HDL cholesterol levels. However, these effects were limited in time, and the high fat content of the diet could lead to negative effects.

A small study published in May 2022 in the American Journal of Clinical Nutrition compared the keto diet and the Mediterranean diet on certain biomarkers. The study found that the keto diet led to a greater decrease in triglycerides, but it also had potential risks from elevated LDL cholesterol and lower nutrient intakes due to avoiding legumes, fruits, and whole grains. Additionally, the keto diet was found to be less sustainable compared to the Mediterranean diet.

Diabetes and Blood Sugar

A 2019 study published in Nutrients found that a low-carbohydrate diet can effectively reduce body weight and improve glycemic control in patients with Type 2 diabetes. However, there is insufficient data on the long-term sustainability, safety, and efficacy of the keto diet or a low-carb regimen. The study also found no evidence that these diets can delay or prevent the onset of Type 1 diabetes.

In a 2021 study published in Nutrients, clinical trial participants on a very low-carb keto diet were found to approach normal blood sugar levels in 24 weeks, which was sooner than another group on a low-calorie diet. Participants were closely monitored for signs of hypoglycemia by physicians, and on average, the keto participants reduced their insulin doses by half.

Cancer Risk

Eliminating all food groups except for one can lead to various health risks, including an increased risk of cancer. Plant-based diets have been shown to greatly reduce the risk of different types of cancer, cardiovascular disease, and diabetes. In contrast, diets heavy in red and processed meats, such as the Keto diet, can increase the risk of stomach and colorectal cancer. The high intake of red meat, which is a known carcinogen, is a significant concern for Harvard MD Aaron Bernstein, who does not recommend this diet due to the increased risk of colon or rectal cancer.

Elevated Cholesterol

The Ketogenic diet promotes foods that are high in saturated fat and cholesterol, which can have harmful effects on heart health. Healthy unsaturated fats from sources like avocados and nuts, which protect brain and heart health, are eliminated from the diet. Studies show that consuming excessive amounts of saturated fat and dietary cholesterol can increase cholesterol levels, clog arteries, and increase the risk of heart disease. While these foods can be part of a balanced diet, it is important to consume them in moderation to avoid compromising health. Elevated cholesterol levels can lead to atherosclerosis, heart attack, and stroke, making the carnivore diet unsuitable for individuals with a personal or family history of cardiovascular disease.


  1. Brehm, B. J., Seeley, R. J., Daniels, S. R., & D'Alessio, D. A. (2003). A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. The Journal of Clinical Endocrinology & Metabolism, 88(4), 1617-1623. Link:
  2. Foster, G. D., Wyatt, H. R., Hill, J. O., McGuckin, B. G., Brill, C., Mohammed, B. S., ... & Klein, S. (2003). A randomized trial of a low-carbohydrate diet for obesity. New England Journal of Medicine, 348(21), 2082-2090. Link:
  3. Shai, I., Schwarzfuchs, D., Henkin, Y., Shahar, D. R., Witkow, S., Greenberg, I., ... & Tangi-Rozental, O. (2008). Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. New England Journal of Medicine, 359(3), 229-241. Link:
  4. Volek, J. S., Sharman, M. J., Gómez, A. L., Judelson, D. A., Rubin, M. R., Watson, G., ... & Kraemer, W. J. (2004). Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women. Nutrition & Metabolism, 1(1), 13. Link:

Rating and Review

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

Ketogenic Diet: A Good Choice?
  • Scientific Evidence
  • Weight Loss
  • Health Impact
  • Balance
  • Affordability
  • Ease and Sustainability


The ketogenic diet is a low-carbohydrate, high-fat diet that has been shown to be effective for short-term weight loss, blood sugar control, and reducing epileptic seizures. However, there is a lack of evidence to support its long-term health benefits or safety, and the highly restrictive nature of the diet can make it difficult to sustain. Eliminating entire food groups means that the diet is not balanced and may lead to nutrient deficiencies. While the keto diet may have some benefits, it should only be followed under the supervision of a medical professional, and will not be suitable for most people, particularly those with pre-existing medical conditions.



  • Research supports some benefits for blood sugar management.
  • Reduction in ketone levels help reduce seizures in those with epilepsy 


  • The ketogenic diet eliminates sugar and refined carbohydrates, but also restricts consumption of nutritious foods like pulses, whole grains, fruit, and starchy vegetables, which are important sources of vitamins, minerals, antioxidants, phytochemicals, and fiber.
  • It’s important to monitor ketone levels, energy levels, and cognitive function when following the diet, and it can be challenging to do so without professional guidance.
  • Muscle loss can occur with the diet, particularly if not followed correctly, and cycling on and off the diet can make it harder to get back into ketosis, which could be harmful for those with insulin resistance.
  • The diet can be challenging to follow when eating out or participating in social activities involving food.
  • There is no long-term research to expand on the benefits found in short-term studies.

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