Pros and Cons of the Ketogenic Diet

Bacon and eggs in skillet
Jill Chen/Stocksy United

The ketogenic diet has become one of the most popular diet trends as it is widely promoted to provide quick and dramatic weight loss. Commonly referred to as the “keto diet,” it promises drastic results in a short period of time. According to research, it may even improve exercise performance in athletes and enable them to lose fat while maintaining muscle mass.

But there is conflicting evidence to support the keto diet as an effective way to reduce obesity, help athletes, or maintain a healthy weight. Additionally, some experts have expressed concerns about the sustainability of the eating plan and its long-term effects of the diet on heart health.

Pros

  • Provides quick weight loss

  • Boosts satiety

  • Can reduce abdominal fat

  • Might improve athletic performance in some

  • Many online resources and recipes

  • May improve health markers such as blood pressure, triglyceride, and cholesterol levels

  • Effective management strategy for some seizure disorders

Cons

  • Hard to maintain because food choices are limited

  • Side effects during initial stages

  • May lead to nutritional deficiencies

  • Healthiest version of the diet can be expensive, inaccessible

  • Contraindicated for certain populations

  • May not be healthy for pregnant women, those with risk factors for health disease, and other medical conditions

Pros

Quick Weight Loss

In looking at some of the studies on keto diets, it appears that weight loss is rapid in the first weeks or months, according to Jennifer McDaniel, MS, RDN, CSSD, LD, registered dietitian and spokesperson for the Academy of Nutrition and Dietetics. Weight loss is a result of both fat loss and water loss.

The keto diet is a very low-carbohydrate, high-fat diet that stimulates metabolic changes in your body. The diet forces your body to use stored fat and fat consumed in the diet for fuel instead of glucose (sugar). This process—called ketosis—can result in an overall decrease in body fat.

Additionally, when carbohydrates are not consumed and stored, your body reduces its water content and overall body weight is decreased as a result.

Sometimes, doctors will recommend a keto diet before weight loss surgery, particularly if the patient must lose weight to safely undergo surgery. In these cases, patients are typically monitored by a physician and a registered dietitian, and they’re usually limited to only 20-30 grams of carbohydrate, says McDaniel.

McDaniel adds that even though studies show weight loss is likely to occur early in a keto diet, studies investigating long-term weight loss and weight maintenance show that the results are similar to those of other types of diet.

While the ketogenic diet may be effective for rapid weight loss, it is unknown if the eating plan is the most effective way to help you maintain a healthy weight for the long-term.

Boosts Satiety

Several studies confirm the keto diet as an effective method for weight loss because keto meals boost satiety—the feeling of satisfaction and fullness. There may be different reasons for this benefit.

First, even though filling fiber-rich foods are extremely limited in these diets, other foods that are recommended on the plan help you to feel full longer. Foods high in fat provide both a satisfying taste and mouthfeel that can help you to eat less. In addition, not only does protein take longer to consume, but it also takes longer to digest—meaning that it also helps you to feel full for a longer period of time after eating.

Also, a ketogenic diet may have a beneficial effect on hunger hormones. One study found that the presence of increased ketone bodies in the blood (a byproduct of ketosis) helps to lower ghrelin levels, which helps to suppress appetite, perceived hunger, and desire to eat.

Reduced Abdominal Fat

Many people who go on a diet to lose weight do so with hopes that weight loss will occur in the abdominal area. Unfortunately, we can't choose where fat loss occurs. However, there is some evidence that a keto diet may target abdominal fat preferentially.

A study published in Nutrition and Metabolism investigated how low-fat diets and very low-carbohydrate diets affect body composition in both men and women. Researchers concluded that very low carbohydrate diets produced better results than low-fat diets for short-term body weight and fat loss, especially in men. They further concluded that there was increased fat loss in the trunk area.

Study authors noted, however, that further evidence is needed to confirm this benefit.

Improved Athletic Performance

A review of ketogenic diets examined if athletic performance could be improved using the low-carbohydrate-high-fat eating program.

According to research, keto diets may help athletes control body weight, reduce body fat, and maintain muscle mass in weight-sensitive sports. In some situations, it appears that endurance athletes adapt to keto diets and are able to burn fat more efficiently than their high-carb, low-fat diet counterparts.

Some keto athletes have also shown similar muscle glycogen content and tissue repair at the same rate as an athlete consuming a more typical higher carb diet. The increased fat oxidation and rate of glycogen return may be of significant benefit to endurance athletes.

Further studies indicated elite male gymnasts using a keto diet maintained maximal strength and significantly reduced body weight and fat. Other findings indicated keto diets in combination with resistance training may allow athletes to maintain muscle and burn fat.

Resources Available Online

If you choose to follow a ketogenic diet, you'll have access to a wide array of free recipes, tips, cooking advice, and other resources online.

There are also many keto-friendly cookbooks available for purchase for those who prefer to cook. For those who choose not to cook, some food companies and commercial diet plans are offering programs, products, and services specifically designed for people following a ketogenic plan.

Lastly, products necessary to test for the presence of ketones are widely available in pharmacies and drug stores.

Improved Health Markers

Some studies have shown that certain health markers may improve when following a keto diet.

One study investigated the long term effects of a ketogenic diet on obese patients. Study authors found that after 24 weeks on the diet patient had reduced body weight, lower BMI, decreased triglyceride level, lower LDL cholesterol, lower blood glucose, and increased HDL cholesterol.

However, it is not clear if all people on a keto diet would experience these benefits since there is a great deal of variation in how to follow a keto diet and the types of food (specifically the types of fat) consumed.

Effective Management of Medical Conditions

The keto diet has been used for decades in conjunction with other medical therapies to treat epilepsy, especially in children. There is a wealth of evidence supporting the use of the eating program to help those who do not respond to medication.

Research is ongoing about the diet's impact on other medical conditions. The keto diet is sometimes used to treat other conditions including headache, neurotrauma, Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis (ALS), cancer, stroke, mitochondrial disorders, brain trauma, psychiatric disorders, autism, and migraines.

Cons

Limited Food Choice

Even though a healthy caloric intake is maintained, the ketogenic diet is highly restrictive. Most foods that are typically associated with a standard American diet are not recommended on the ketogenic eating plan. As a result, you need to substantially change the way you eat to stay on this program.

The keto diet avoids all grains and grain products, beans and legumes, most fruits, starchy vegetables, alcohol, and all sugars. Certain milk and dairy along with some fats are also eliminated.

Because it’s such a strict diet, many people aren’t able to maintain it for long periods of time. Diets that are restrictive often result in rebound weight gain, because many people eventually start to crave the foods they’re avoiding. 

In addition, people who think they are following the plan correctly may not be, according to McDaniel. Enjoying a piece of cake at your child’s birthday or grabbing a granola bar before a long flight would quickly kick yourself out of ketosis. As a result, your body would begin burning glucose for fuel instead of fat.

Because the diet removes essential nutrients, some registered dietitians indicate keto diets work only short-term and can be unhealthy. In addition, extreme restriction with any kind of diet usually backfires sending the dieter into a downward spiral of guilt and frustration from another failed diet attempt.

Side Effects

Another factor that makes the keto diet hard to maintain is the onset of side effects, usually during the first week of the program when your body is getting into and adjusting to ketosis.

The transition into ketosis may trigger side effects including fatigue, weakness, light-headedness, headaches, mild irritability, and gastrointestinal symptoms.

While most people eventually adjust to ketosis, if you don't maintain carbohydrate levels low enough, your body may go in and out of the fat-burning state. As a result, you may experience the symptoms again.

Study results also discovered some negatives for athletes using the keto diet. It appears elevated levels of free fatty acids and ammonia showed up in the bloodstream during exercise.

High levels of free fatty acids and ammonia may contribute to impaired metabolism and central nervous system fatigue. Apparently, several months are required for an athlete to adapt to keto diets for positive metabolic changes and muscle glycogen to occur.

In order for endurance athletes to improve their exercise performance using a keto diet, an adaption period of several months is recommended. Without long-term adaption to the keto diet, an athlete would experience adverse effects including reduced muscle glycogen, hypoglycemia, and impaired athletic performance, according to research results. 

Nutritional Deficiencies

The keto diet is very restrictive and eliminates essential nutrients such as fiber or vitamin C coming from grains, beans and legumes, most fruits, and some vegetables. Dairy products that provide calcium and vitamin D are also avoided. McDaniels says there’s always a risk for nutrient deficiencies when entire groups of foods are eliminated from the diet.

For this reason, many registered dietitians recommend working with a healthcare professional to make sure you are getting the nutrition you need.

If you are set on trying a keto diet, McDaniel highly recommends speaking with your healthcare provider first and then continuing to work with a registered dietitian, who can help ensure that you don’t become deficient in any nutrients.

Expensive and Inaccessible

McDaniel recommends that you make sure the fats you choose are healthy. While some people who are interested in the diet look forward to eating bacon, beef, and butter, those foods are high in saturated fat. Healthier versions of the diet recommend foods such as coconut oil, MCT oils, avocado, and other plant-based fats.

These foods are often more expensive than foods that are commonly consumed in a typical American diet, like rice, pasta, bread, and processed foods. Some keto-friendly foods may also not be available in all grocery stores.

For example, packaged coconut might be available at your local market, but coconut oil may not be. Avocados are found in most produce sections, but avocado oil can be hard to find and very expensive.

Health Concerns and Contraindications

The ketogenic diet appears to be safe in the short term based on small studies, according to McDaniel. However, she says that we don't have much evidence that it's safe in the long-term She adds that studies that have focused on safety have either been small or performed on animals.

McDaniel indicates the Academy of Nutrition and Dietetics currently doesn’t recommend the keto diet for people with or at high risk for kidney disease, osteoporosis, or high LDL cholesterol. Those who are on diabetes medications should speak to their healthcare team before going on the diet because medications may need to be adjusted.

Additionally, according to medical researchers, the ketogenic diet is contraindicated in patients with pancreatitis, liver failure, disorders of fat metabolism, primary carnitine deficiency, carnitine palmitoyltransferase deficiency, carnitine translocase deficiency, porphyrias, or pyruvate kinase deficiency. 

Lastly, there are conflicting studies about the impact of a ketogenic diet on women who are pregnant or wishing to become pregnant. While some research has suggested that a low-carbohydrate diet may improve hormonal balance to achieve pregnancy, other animal studies have suggested that following a ketogenic diet during pregnancy may have negative effects on the developing fetus.

Was this page helpful?

Article Sources

Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  • Dashti, H. M., Mathew, T. C., Hussein, T., Asfar, S. K., Behbahani, A., Khoursheed, M. A., … Al-Zaid, N. S. (2004). Long-term effects of a ketogenic diet in obese patients. Experimental and clinical cardiology9(3), 200–205. PMID: 19641727

  • McGrice, M., & Porter, J. (2017). The Effect of Low Carbohydrate Diets on Fertility Hormones and Outcomes in Overweight and Obese Women: A Systematic Review. Nutrients9(3), 204. doi:10.3390/nu9030204

  • Paoli, A et al.  Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. European Journal of Clinical Nutrition. May 2014; Epub ahead of print. doi:10.1038/ejcn.2013.116


  • Paoli A, Ketogenic Diet for Obesity: Friend or Foe?, International Journal of Environmental Research and Public Health, 2014

  • Stubbs, B. J., Cox, P. J., Evans, R. D., Cyranka, M., Clarke, K., & de Wet, H. (2017). A Ketone Ester Drink Lowers Human Ghrelin and Appetite. Obesity (Silver Spring, Md.)26(2), 269–273. doi:10.1002/oby.22051

  • Sumithran, P., Prendergast, L. A., Delbridge, E., Purcell, K., Shulkes, A., Kriketos, A., & Proietto, J. (2013). Ketosis and appetite-mediating nutrients and hormones after weight loss. European Journal of Clinical Nutrition, 67(7), 759–764. doi:10.1038/ejcn.2013.90

  • Sussman, D., Ellegood, J., & Henkelman, M. (2013). A gestational ketogenic diet alters maternal metabolic status as well as offspring physiological growth and brain structure in the neonatal mouse. BMC pregnancy and childbirth13, 198. doi:10.1186/1471-2393-13-198

  • Sussman, D., van Eede, M., Wong, M. D., Adamson, S. L., & Henkelman, M. (2013). Effects of a ketogenic diet during pregnancy on embryonic growth in the mouse. BMC pregnancy and childbirth13, 109. doi:10.1186/1471-2393-13-109

  • Urbain P et al., Impact of a 6-Week Non-Energy-Restricted Ketogenic Diet on Physical Fitness, Body Composition and Biochemical Parameters in Healthy Adults, Journal of Nutrition & Metabolism, 2017

  • Wajeed Masood, Kalyan R. Uppaluri. Ketogenic Diet. StatPearls Publishing LLC. 2019