The Ketogenic Diet

The ketogenic diet is one of the most popular diets right now. There are many supposed benefits to the ketogenic diet, but most are based on short-term evidence.

The ketogenic diet is one of the most popular diets right now. There is a lot of information out there and sometimes it’s hard to sift through it all to get to the truth. There are many supposed benefits to the ketogenic diet, and definitely some disadvantages. The problem is that most of these pros and cons are based on short-term evidence. There aren’t many long-term studies relating to the ketogenic diet and its effects on overall health. 

What is the ketogenic diet?

The ketogenic diet is a very low-carbohydrate, high-fat diet that was first used to treat pediatric patients who suffered from epilepsy.1 Today, this diet has been popularized as a weight-loss plan. Typically, the goal with the ketogenic diet is to eat 70-80% of calories from fat, 5-10% from carbohydrate, and 10-20% from protein.2 The current recommended ranges for a healthy, balanced diet are 20-35% of calories from fat, 45-65% from carbohydrate, and 10-35% from protein. Even people with diabetes, who have to control their carbohydrate intake, have a much higher recommended carb range than the ketogenic diet, at 40-50% of calories.

The body’s main source of fuel is glucose, which is what all consumed carbohydrates are broken down to during digestion. The goal of the ketogenic diet is to get into a state of ketosis, which means the body will use fat as its main source of fuel, rather than glucose. When dietary carbohydrates are severely limited for a sufficient amount of time, glucose reserves are depleted and the liver will start to produce ketone bodies for fuel.Although this is not the typical way the body supplies fuel for the brain and muscles, people following the ketogenic diet consider ketosis a marker of success.


Weight Loss

There is strong evidence to support that the ketogenic diet leads to weight loss in the short-term. There are studies that show that people who follow a low-carbohydrate diet experience greater weight loss in the first 3-6 months when compared to people who have a balanced diet. There are many hypotheses for why this weight loss happens, but no solid evidence has been found to support any of them. Some researchers believe that this weight loss is simply due to reduced calorie intake in general, rather than the low-carbohydrate nature of the diet. Other researchers point to evidence that suggests that ketones and a decrease in hormones that control appetite could lead to the weight loss.3 After the 3-6 month time frame, it is hard to say if weight loss will be greater in the ketogenic diet than any others. A systematic review, which looks at multiple research studies, found that those following a ketogenic diet and those following low-fat diets had about the same weight loss at 12 months.4

Improved Health Parameters

Recent short-term studies have shown that the ketogenic diet has positive effects on several health parameters. The diet has been shown to improve lipid blood levels. Specifically, it has been shown to decrease blood triglycerides, lower total cholesterol, and increase HDL (“good”) cholesterol.3 Insulin resistance and high blood pressure have also improved in some short-term studies. These improvements go hand-in-hand with the weight loss, as these parameters are associated with excess weight.5

Other very new, emerging evidence shows this diet may benefit acne, neurological diseases, cancer, and PCOS. The current studies suggest that reduction in insulin levels could be one possible mechanism for these improvements.3

The outcomes of these studies are very inconsistent and require much more research to determine potential benefits.


Difficult to maintain

Perhaps the most glaring con is that the ketogenic diet is hard to maintain long-term. Typically, the diet requires eating less than 30-50 grams of carbohydrates in a day. Fifty grams of carbohydrates is equivalent to one medium-size bagel. Any diet that requires essentially cutting out a large food group is going to be difficult. Plus, this diet requires diligent attention to everything eaten to maintain a state of ketosis. That constant attention and planning is challenging and time consuming.

Negative effects on general health

The diet cuts out whole grains, fruit, starchy vegetables, and legumes because of their carbohydrate content. Many different vitamins, minerals, and fiber come from these foods, so nutrient deficiencies could arise which could cause negative health outcomes. 

Since the diet allows high fat, people may eat options high in saturated fat (fatty meats, processed meats, butter). High saturated fat could cause higher LDL (“bad”) cholesterol. A meta-analysis (which is a method of evaluating many research studies) found that LDL levels were significantly higher among the groups following the ketogenic diet in several short term studies.6

Another possible risk of the ketogenic diet is potential kidney damage, although, the evidence is inconsistent and researchers are not in agreement on this. There have been animal studies that show renal damage, but other human studies do not show damage to renal function.3

Another negative effect of the ketogenic diet is on athletic performance. According to a study in the Journal of Sports Medicine and Physical Fitness, short-term ketogenic diets negatively impact strength training exercise performance when compared to a high-carbohydrate diet. The study found that following a ketogenic diet reduces cardiovascular performance.7


Another con to this diet is that there is so much uncertainty around it. Such limited research and a total lack of long-term studies means we don’t really know how this diet will affect health, especially after 12 months. This leaves a lot of unanswered questions: are there negative long-term effects? Are there any safety issues for healthy individuals? How would this diet affect individuals with other existing health complications?

Bottom Line

Restrictive diets aren’t typically effective in the long-run. The ketogenic diet will cause short-term weight loss, but we need to be thinking in the long-term when it comes to our health. Following a less restrictive, balanced eating pattern that includes a variety of foods will be easier to maintain throughout life, and may be more effective in the long run.

If you still want to try the diet for short-term weight loss, here are some questions to reflect on: Is this strict diet realistic for your lifestyle? Do you have any medical conditions that might be affected by this eating pattern? Have you consulted with your doctor and/or a dietitian to discuss if this is right for you?


1. Randall R, Groveman S. The Ketogenic Diet for Epilepsy—Learn about the diet, the medical conditions it’s used to treat, and its mechanism of action. Today’s Dietitian. 2016;18(5).

2. Harvard T.H. Chan School of Public Health. Diet Review: Ketogenic Diet for Weight Loss. Accessed November 1, 2018.

3. Paoli A, Rubini A, Volek JS, et al. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. Eur J Clin Nutr. 2013;67(8):789-796.

4. Sumithran P, Proietto J. Ketogenic diets for weight loss: A review of their principles, safety and efficacy. Obes Res Clin Pract. 2008;2(1):1-13.

5. Schwingshackl L, Hoffmann G. Comparison of effects of long-term low-fat vs high-fat diets on blood lipid levels in overweight or obese patients: a systematic review and meta-analysis. J Acad Nutr Diet. 2013;113(12):1640-61.

6. Bueno N, de Melo I, et. al. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr. 2013;110(7):1178-87.

7. Weiss E, Wroble K, Trott M, et al. Low carbohydrate, ketogenic diet impairs anaerobic exercise performance. J Sports Med Phys Fitness. 2018. DOI: 10.23736/S0022-4707.18.08318-4.

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