Pros and Cons of the Ketogenic Diet


Verywell / Alexandra Shytsman

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.

There is conflicting evidence to support the keto diet as an effective way to reduce obesity, help athletes, or maintain a healthy weight, however. Additionally, some experts have expressed concerns about the sustainability of the eating plan and its long-term effects of the diet on heart health. Here's a close look at the pros and cons of the ketogenic diet.

  • 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

  • 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


The keto 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.

Quick Weight Loss

The keto diet is a very low-carbohydrate, high-fat diet that triggers metabolic changes in your body. When carbohydrates are not consumed and stored, your body reduces its water content and overall body weight is temporarily decreased as a result; this balances out after the first week or two.

There are four potential physiological reasons for rapid weight loss in the first weeks and months of the keto diet:

  • Appetite reduction/satiety and altered hunger hormones
  • Decreased fat storage and increased fat utilization
  • Increased fat burning efficiency,
  • Increased thermic effect and calorie utilization required to break down protein as fuel and convert it to glucose (as well as fat).

Studies suggest that the keto diet is a better alternative to a very low-calorie diet that doctors prescribe to help patients lose weight prior to weight loss surgery. In a comparison study, the keto diet group had a greater reduction in body mass index (BMI) and significantly reduced post-op hospital stay: only 2.8% exceeded 3 days compared to 10.8% in the very-low-calorie diet group.

Body Mass Index (BMI) is a dated, biased measure that doesn’t account for several factors, such as body composition, ethnicity, race, gender, and age. 


Despite being a flawed measure, BMI is widely used today in the medical community because it is an inexpensive and quick method for analyzing potential health status and outcomes.

While weight loss is likely to occur early in a keto diet, the big question is whether long-term weight loss and weight maintenance can be sustained. Every person who resumes old habits will regain weight regardless of the methods used to lose weight. However, one study on weight loss maintenance with the keto diet successfully paired two cycles of the keto diet with a Mediterranean maintenance eating plan.

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 such as:

  • High-fat foods promote satiety. While filling fiber-rich foods are extremely limited on the keto diet, 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, which can help you to eat less.
  • Protein takes longer to consume and digest. This helps you to feel full for a longer period of time after eating.
  • A keto 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. Researchers concluded that very low-carbohydrate diets produced better results than low-fat diets for short-term body weight and fat loss. They further concluded that there was an increase in 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:

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 counterparts. Other keto athletes have also shown similar muscle glycogen content and tissue repair at the same rate as an athlete consuming a typical higher carb diet. The increased fat oxidation and rate of glycogen return may be of significant benefit to some 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, meal plans, tips, cooking advice, and other resources online. There are also many keto-friendly cookbooks available for purchase for those who prefer to cook. In addition, products that test for the presence of ketones are widely available in pharmacies and drug stores.

For those who choose not to cook, some food companies and commercial diet plans offer programs, products, and services specifically designed for people following a ketogenic plan.

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, patients had reduced body weight, lower BMI, decreased triglyceride levels, 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.

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


As with all diets, the ketogenic diet has its drawbacks. Research is ongoing about the diet's impact on certain medical conditions, and findings are often mixed. And because it’s such a strict diet, many people aren’t able to sustain it. Diets that are restrictive often result in rebound weight gain, because many people eventually start to crave the foods they’re avoiding

Limited Food Choice

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.

Although an appropriate 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 keto plan. As a result, you need to substantially change the way you eat to stay on this program.

Because the diet removes essential nutrients, many nutrition professionals reserve keto diets for medical nutrition therapy. In addition, extreme restriction with any kind of diet usually backfires, sending people into a spiral of guilt and frustration from another failed diet attempt.

Enjoying a piece of cake at a birthday party or grabbing a granola bar before a long flight would quickly kick you out of ketosis. As a result, your body would begin burning glucose for fuel instead of fat.

Side Effects

Another factor that makes the keto diet hard to maintain is the onset of side effects, usually during the first week or so of the program as your body gets accustomed to ketosis. While most people eventually adjust, if you don't maintain low enough carbohydrate levels, your body may go in and out of the fat-burning state. As a result, you may experience the symptoms again.

Often referred to as the "keto flu," side effects experienced during the initial phase of the keto diet may include:

  • Exercise intolerance
  • Fatigue
  • Gastrointestinal symptoms
  • Headaches
  • Insomnia
  • Light-headedness
  • Mild irritability
  • Nausea
  • Weakness

Study results have also discovered some risks for athletes using the keto diet. It appears elevated levels of free fatty acids and ammonia showed up in the bloodstream during exercise, which may contribute to impaired metabolism and central nervous system fatigue.

Evidently, several months are required for an athlete to adapt to the keto diet for positive metabolic changes and muscle glycogen to occur. In order for endurance athletes to improve their exercise performance on this plan, 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.

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.

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

If you decide to try the keto diet, consult your healthcare provider first and then seek assistance from a nutrition professional who can help prevent nutrient deficiencies.

Expensive and Inaccessible

Choosing healthy fats is important. 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 keto diet recommend foods such as coconut oil, MCT oils, avocado, raw, unsalted nuts, 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. Additionally, 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 expensive.

Health Concerns and Contraindications

The ketogenic diet appears to be safe in the short term based on small studies. However, large-scale studies on long-term effects are not available.

There are conflicting studies about the impact of a ketogenic diet on those who are pregnant or trying 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.

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. 

Those with diabetes taking insulin or other hypoglycemia drugs should not begin this diet without working with a physician to adjust their medications.

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By Darla Leal
Darla Leal is a Master Fitness Trainer, freelance writer, and the creator of Stay Healthy Fitness, where she embraces a "fit-over-55" lifestyle.