Eggs in a bowl as an example of food for a keto diet

Keto Diet: Advantages and Disadvantages

Medically reviewed on January 4, 2024 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

Typically, the majority of most people’s diets contain a large amount of carbohydrates—sugar molecules that provide the body with readily available energy. Dietary reference intakes (DRIs), which are scientifically developed recommended nutrient values, suggest that an adult’s diet should have 45 to 65 percent of total calories coming from carbs, 20 to 35 percent coming from fat, and 10 to 35 percent coming from protein.[1]

The keto diet, however, flips these recommendations.

A ketogenic diet is low in carbs and high in healthy fats, with moderate protein intake (not to be confused with a low-carb, high-protein diet). Historically, healthcare workers have prescribed ketogenic eating plans to control such conditions as diabetes, epilepsy, cancer, polycystic ovary syndrome (PCOS), and Alzheimer’s disease.[2]

Does this low-carb diet really work if you want to lose weight? Below, we explore the keto diet’s advantages and disadvantages.

The Mechanisms Behind the Keto Diet

The theory behind the keto diet centers around depriving the body of glucose, or sugar—the primary source of energy for the body, followed by fats, and then proteins.[2]

When carbohydrate stores are depleted, the body turns to fats, which are broken down into glycerol and fatty acids. Fatty acids can then be converted into ketones, which the body can use for energy during periods of fasting, prolonged exercise, and/or carb deficiency.[3]

While protein primarily plays a role in maintaining the health of muscles, bones, and tissues, the body can also use it for fuel in the case of a prolonged energy deficit, such as starvation or low-carb diets—like keto.[2]

With a reduced carbohydrate intake, the body uses glucose reserves in the liver and muscles to power the brain and various physiological processes. After three to four days, when glucose levels fully deplete, the hormone insulin also dwindles. As a result, the body turns to fat (ketones) to fuel itself.[2]

As ketone levels increase and travel through the bloodstream to fuel various tissues and organs, the body enters a state of ketosis. During this metabolic state, the body burns fat for energy.[2,4] But, where does fat go when you lose weight on this diet?

Accordingly, the keto diet encourages fat burn with a diet that consists of 70 to 80 percent healthy fats, 10 to 20 percent proteins, and 5 to 10 percent carbohydrates—staying under 50 grams of carbs a day.[4]

The Advantages of a Keto Diet

People with health conditions that can be improved or managed through weight loss and/or altered brain function may benefit from adopting a keto diet. While individual responses to ketosis vary, and it may not be suitable for everyone, there is evidence suggesting its potential advantages for certain health conditions, which is explored below.[4]

1. Epilepsy

Epilepsy is a type of brain disease in which the communication between nerves becomes impaired, causing seizures. The keto diet changes how the brain uses energy and, thus, many healthcare providers prescribe this eating plan to children and infants with epilepsy who are unresponsive to medication.[5]

A ketogenic diet has been shown to reduce seizures by influencing the “excitability” of the brain, although the exact mechanisms are not yet fully understood. That said, roughly 40 to 50 percent of children with epilepsy who follow a ketogenic diet experience 50 percent fewer seizures. Even better, 10 to 20 percent of children achieve a 90 percent reduction.[5]

2. Neurological Conditions

Other brain-related conditions, like Alzheimer’s disease, autism spectrum disorder, and glioblastoma may also respond to a ketogenic diet:

  • Alzheimer’s disease – People with Alzheimer's disease experience declines in memory, thinking, organizing, and learning skills. Their brains also have a difficult time using glucose as fuel. Thus, ketones may help to improve brain function in people with Alzheimer’s disease. In one research study, participants with mild Alzheimer's disease followed a ketogenic diet for three months. Results found that each patient's cognitive scores improved while following a low-carb diet.[6]
  • Autism spectrum disorder – Autism is a neurodevelopmental disease that can impact social interactions and communications. Studies have found that using a ketogenic diet as a dietary intervention therapy for those with autism may improve core symptoms, like sociability, and comorbidities, like seizures, attention deficit hyperactivity disorder (ADHD), compulsive behavior, and abnormal sleep.[7]
  • Glioblastoma – As a type of cancerous brain tumor, glioblastoma, spreads rapidly through the brain, causing such symptoms as seizures, speech problems, memory problems, and mood changes, among others. Research studies have found that a ketogenic diet, when used in conjunction with traditional cancer therapies, may help to protect surrounding brain cells, reduce tumor size, improve sleep and mood, and improve the chance of survival. However, in some cases, the cancer can adapt to the diet, making it ineffective.[8]

3. Type 2 Diabetes

Type 2 diabetes is a condition that’s characterized by high blood sugar levels, due to insulin resistance and/or insufficient insulin production. As a result, those with type 2 diabetes are likely to experience [9]:

  • Increased thirst
  • Frequent urination
  • Increased levels of hunger
  • Fatigue
  • Slow healing of wounds
  • Tingling or numbness in the extremities
  • Blurred vision
  • Dry skin
  • Unexplained weight loss

To manage type 2 diabetes, patients may work with a healthcare team to lower blood sugar levels with lifestyle changes and medication.[9]

According to research, low-carb diets like keto are effective in managing blood sugar levels and facilitating weight loss for some people. That said, very low blood sugar levels can be harmful to those with diabetes, causing weakness, confusion, headaches, and/or seizures.[10]

4. Metabolic Syndrome and Heart Disease

Metabolic syndrome and heart disease are tightly linked. More specifically, having metabolic syndrome also increases your risk of cardiovascular disease, as well as stroke and type 2 diabetes.[11]

That said, a keto diet may help to improve both conditions.

Metabolic syndrome is characterized by having at least three of the following conditions [11]:

  • Excess abdominal weight
  • Hypertriglyceridemia
  • Low levels of high-density lipoprotein (HDL) cholesterol
  • Elevated blood sugar levels
  • High blood pressure

Fortunately for those who want to lose weight, studies have shown that ketogenic diets can support blood sugar management and weight loss.[12]

See related: Fat Loss vs. Weight Loss

The Disadvantages of a Keto Diet

Ketogenic diets have been shown to help support and manage weight loss, blood sugar levels, insulin levels and usage, and certain neurological conditions. However, following a low-carb diet in the long term does carry some additional risks.

1. Hypoglycemia

For people with type 2 diabetes, there is a significant risk of developing hypoglycemia—blood sugar levels that are below 70 milligrams per deciliter. This condition is particularly dangerous for individuals taking diabetes medications or insulin.[10,13]

That said, low blood sugar levels can also impact people who don’t have diabetes. Signs that your blood sugar levels have dropped include [14]:

  • Shaking or trembling
  • Weakness
  • Sweating and chills
  • Extreme hunger
  • Faster heart rate
  • Dizziness or lightheadedness
  • Confusion or trouble concentrating
  • Anxiety or irritability
  • Color draining from the skin
  • Tingling or numbness in your lips, tongue, or cheeks

In severe cases, someone with hypoglycemia may experience seizures, slurred speech, vision problems, trouble with coordination, and loss of consciousness.[14]

2. Nutrient Deficiency

When following any type of restrictive diet, you may be at risk of a nutrient deficiency. In the case of keto, it’s recommended to cut out high-carb fruits, vegetables, whole grains, and legumes; although the diet does allow for [15,16]:

  • Berries
  • Leafy greens
  • Cauliflower
  • Broccoli
  • Brussels sprouts
  • Asparagus
  • Bell peppers
  • Onions
  • Garlic
  • Mushrooms
  • Cucumber
  • Celery
  • Summer squashes

All that said, carbohydrate restrictions can profoundly impact the quality of your diet. Low-carb diets are often deficient in [16]:

  • Thiamin – Plays a role in maintaining a healthy nervous system
  • Folate – Helps to support cell growth, specifically during pregnancy and infancy
  • Vitamin A – Provides immune system, skin, and vision support
  • Vitamin E – Helps protect the cells from oxidative damage
  • Vitamin B6 – Supports blood health and the transportation of oxygen through the body
  • Calcium – Manages bone health, muscle function, and blood clotting
  • Magnesium – Helps metabolize nutrients and support muscle, nerve, and bone health
  • Iron – Supports oxygen transport and energy metabolism
  • Potassium – Maintains fluid balance and heart function

Micronutrient deficiencies can cause cognitive impairment and poor growth, as well as an increased risk of morbidity, such as degenerative diseases.[17]

3. Keto Flu

In the week after starting a ketogenic diet, some people can experience a combination of symptoms, colloquially referred to as the “keto flu.” These include [18,19]:

  • Headache
  • Foggy brain
  • Fatigue
  • Irritability
  • Nausea
  • Diarrhea
  • Difficulty sleeping
  • Constipation
  • Intestinal pain or bloating
  • Muscle cramps and/or weakness

The cause is unknown, and there is very little scientific research on the condition. Some propose that the detox effect, carb withdrawal, or a change in the gut microbiome may play a role.[18]

One study that gathered consumer feedback via online forums observed that symptoms typically resolve within four weeks. [19]

Gain Valuable Dietary Insights With Everlywell

Following a keto diet can help facilitate weight loss and may improve certain medical conditions. However, it’s important to monitor its effects on the body to avoid nutrient deficiencies and risks to your overall health.

At Everlywell, we provide a collection of at-home tests related to diet to help assess your metabolic rate, food sensitivities, and cholesterol, vitamin, and lipid levels. If weight loss is the goal, the Everlywell online weight management program provides you with one-on-one appointments with licensed healthcare providers who can guide you through the different stages of weight loss and help customize your diet, lifestyle habits, and medications to meet your goals.

Start the change today.

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  3. BridgetChapple. Ketones and diabetes. Diabetes UK. URL. Accessed January 2, 2024.
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Jordan Stachel, M.S., RDN, CPT is most fulfilled when guiding others towards making stepwise, sustainable changes that add up to big results over time. Jordan works with a wide variety of individuals, ranging in age from children to the elderly, with an assortment of concerns and clinical conditions, and has written for publications such as Innerbody. She helps individuals optimize overall health and/or manage disease states using personalized medical nutrition therapy techniques.
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