The ketogenic diet has exploded in popularity recently, buzzing around the internet as the latest dietary fad. But unlike other diet plans, the Ketogenic (or keto) Diet isn’t actually new. This low-carbohydrate diet is similar to the Atkins Diet of the 1970s and the South Beach Diet of the late 1990s. Same diet, different name. It's a high-fat, very-low-carbohydrate diet that forces the body to switch its primary fuel source from glucose (derived from carbohydrates) to ketones (derived from fat). This article aims to provide a comprehensive overview of the ketogenic diet, exploring its potential benefits, associated risks, and long-term sustainability, while making maximum use of the information provided.
What is the Ketogenic Diet?
The keto diet aims to force your body into using a different type of fuel. Burning fat seems like an ideal way to lose pounds. The recommendation for the Ketogenic Diet is that you should consume only about 5-10% of your daily calories from carbohydrates, 70% of your calories from fats, and the remaining 20-25% from protein. By way of comparison, the dietary recommendations from the Institute of Medicine (IOM) are 45-65% of daily calories from carbohydrate, 20-35% from fat, and 10-35% from protein. The IOM recommendations are backed by groups like the American Heart Association, American Cancer Society, American Diabetes Association, the Surgeon General’s Office, and the overwhelming majority of Registered Dietitians.
How it Works: Ketosis
Because dietary carbohydrate is extremely limited on the keto diet, the body cannot rely very much on carbohydrate as a fuel source for energy. This triggers a metabolic state called ketosis - a response by the liver to produce ketones, which are made from fatty acids. The ketones travel through the blood where they are used as a primary fuel source by the central nervous system (brain and spinal cord) and used to a lesser extent as fuel by other tissues. Ketosis will also result in the body’s use of protein (e.g. muscle) as fuel to some extent.
Different Types of Ketogenic Diets
Ketogenic diets can be broken down into four different categories:
- The "Classic" Ketogenic Diet: The “classic” ketogenic caloric intake is typically made up of a ratio of 4:1 or 3:1 grams of fat to combined grams of carbohydrates and protein. A 4:1 ratio would break down caloric intake to 90% from fat, 6% from protein, and 4% from carbohydrates. The difficulty with a classic ketogenic diet is palatability. All foods must be weighed on a scale to achieve a relative weight distribution of 4 grams of fat for every 1 gram of combined protein and carb eaten throughout the day. In other words, you will likely need to avoid all carb-rich foods (like pasta, potatoes, fruit, etc.). A typical meal might look like half an avocado with a small piece of salmon cooked in a lot of olive oil with a side salad. It will all be topped with a cream sauce made with heavy cream and cheese.
- Medium Chain Triglyceride (MCT) Diet: This type of ketogenic diet allows the individual to increase the number of carbohydrates and proteins in the diet. An increase in carbohydrates and protein make the diet more palatable. However, to keep ketone levels elevated, fat intake should come from medium-chain triglycerides. Medium-chain triglycerides help with ketosis because they are more easily absorbed and converted to ketones than long-chain triglycerides. This diet generally still requires a scale for weighing food. It's defined by a ratio closer to 3 grams of fat for every 1 gram of combined protein and carb (generally with a focus on more protein than carbs). In other words, you'll still avoid most carb-rich foods except for maybe one or two servings per day.
- Modified Atkin's Diet: The modified Atkin’s diet is different from a typical Atkin’s diet because it replaces some of the protein in Atkin’s diet with fat. The typical ratio of fat to protein and carbohydrates is 1:1. This diet is the more user-friendly keto diet and likely the most popular. These diets generally avoid all starchy foods (pasta, rice, potatoes, bread, corn, peas, beans and legumes). Desserts and any other high-carb foods are also not part of the diet.
- Low Glycemic Index Ketogenic Diet: The glycemic index measures the effect that different types of carbohydrate foods have on blood sugar. Simple carbohydrates like sugar are rapidly absorbed and therefore have a high glycemic index. Complex carbohydrates like whole grains are more slowly absorbed and therefore have a lower glycemic index.
Potential Benefits of the Ketogenic Diet
The Ketogenic Diet has exploded in popularity recently because it does cause rapid, and sometimes dramatic weight loss. It’s not unusual for people to lose 8-12 pounds during the first couple of weeks. The internet is filled with testimonials from people who have supposedly stuck with it long enough to lose 50 lbs or more in just a few months. Combined with the perception of scientific validity, it’s no wonder why this is the latest fad.
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There is good evidence that ketogenic diets help with weight loss, epilepsy, type 2 diabetes, and improvement in cardiometabolic risk factors.
Weight Loss: Research suggests that the keto diet helps people cut calories because the diet doesn't include many foods that people are likely to overeat. A low-calorie version of keto helped overweight and obese adults lose an average of 22 pounds in four weeks or less, according to a review published in November 2019.
Epilepsy Management: The keto diet was first used as a treatment for pediatric drug-resistant epilepsy to reduce seizures in the 1920s. The keto diet is used to help reduce the frequency of epileptic seizures in children. For many families, the ketogenic diet (KD) is more than a short-term intervention - it can become a long-term therapy for managing seizures when medications fall short.
Type 2 Diabetes: Ketogenic diets can lead to temporary improvements in important risk factors like blood glucose.
Cardiometabolic Risk Factors: Ketogenic diets can lead to temporary improvements in important risk factors like HDL and LDL cholesterol levels, inflammatory markers, and waist circumference. Some people will actually find that their high-density lipoproteins (HDL) - the good cholesterol - go up and their triglycerides go down.
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Risks and Considerations of the Ketogenic Diet
But take a closer look and you will see that it isn’t all it claims to be. For most people, the perceived ‘pros’ of the Ketogenic Diet are outweighed by the following ‘cons.'
Short-Term vs. Long-Term Side Effects
Families often report short-term issues when starting KD, such as constipation, diarrhea, nausea, vomiting, weight changes, hunger, lethargy, hypoglycemia, dehydration, or food refusal. These are usually most noticeable early as the body adapts. Over the long term, concerns may include slowed growth, constipation, elevated lipids, kidney stones, osteopenia, and carnitine deficiencies. Some complications - like metabolic acidosis, electrolyte imbalances, and vitamin/mineral deficiencies - can occur at any stage, making regular monitoring essential.
In the early weeks, the most common challenges were digestive upset - such as constipation, diarrhea, or stomach pain - which affected nearly half of patients. About one in four experienced neurological effects like tiredness or sluggishness. Hypoglycemia was reported occasionally but was usually short-lived, while issues like acidosis and kidney stones were rare.
Over the longer term, digestive problems continued to be the most common concern. Some children experienced less lethargy but more appetite loss. Bone density changes and kidney complications were also reported in some studies.
Weight Loss: Water vs. Fat
First, if one is trying to lose weight, they should be striving to lose fat weight. The scale does not tell us what kind of weight we are losing. Our body is about 60% water by weight. Carbohydrate is stored in our body as a substance called glycogen, which is found mostly in muscle and liver cells. Each gram of glycogen we store is accompanied by two grams of water. When we restrict carbohydrate intake, glycogen levels are depleted, and we rapidly lose a lot of water weight via increased urination. This does not make us healthier, but it does make us somewhat dehydrated.
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Macronutrient Tracking and Calorie Restriction
Second, following the Ketogenic Diet means carefully tracking your macronutrients (protein, fats, carbs, and water), in addition to some micronutrients like vitamins and minerals. It can be an arduous task that makes simple calorie counting seem like a breeze. While most proponents of keto tout that calorie counting isn’t the main focus, the fact is that most people on this plan are also restricting calories. Any diet that creates a calorie deficit is likely to induce weight loss. While this makes it somewhat difficult to determine if the weight loss is the result of calorie restriction or from being in ketosis, The Cooper Institute’s position is that it is the former, not the latter.
Lack of Long-Term Scientific Data
Third, there is a lack of long-term scientific data to support this diet. Most diet studies (as well as testimonials) are short-term, lasting only weeks or months. The short-term studies on Ketogenic diets have shown short-term weight loss as well as temporary improvements in important risk factors like HDL and LDL cholesterol levels, blood glucose, inflammatory markers, and waist circumference. However, any dietary approach that leads to weight loss will tend to show these same types of improvements. To date, there are no significant studies to show that the Ketogenic diet leads to long-term weight control or improved health. In fact, some of the latest research suggests that it may be harmful in the long run.
Specific Keto Cons
- Lack of variety: So many foods are limited with this approach that you will likely soon tire of eating the same things over and over again.
- Lack of fiber: Complex carbohydrates are the only source of dietary fiber! Since carbohydrate intake is very limited with the Ketogenic diet, you will be consuming a very low fiber diet by default. Low fiber diets are strongly associated with an increased risk of constipation, hemorrhoids, type 2 diabetes, cardiovascular disease, and digestive cancers.
- Lack of essential nutrients: Ketogenic diets are notoriously low in several essential nutrients including vitamins C and D, as well as some of the B vitamins. Calcium is also lacking. Most Ketogenic diet enthusiasts remain unaware that complex carbohydrates contain hundreds of beneficial substances called phytochemicals; which are naturally occurring non-nutrients that help to prevent disease.
- Not a long-term solution: The weight loss from the Ketogenic approach is typically temporary, not permanent. When you change your eating habits short-term, your weight will also change short-term. The goal should not be short-term weight loss, but rather, long-term weight control.
- Fatigue and irritability: A Ketogenic diet increases the likelihood of hypoglycemia (low blood glucose levels) and can trigger what is known as the keto-flu. Keto flu symptoms appear a few days after starting the diet. This eventually goes away once your body adjusts to your eating changes. Symptoms may include headaches, fatigue, irritability and more unpleasant symptoms.
- Inability to perform regular sustained exercise: Carbohydrate is a major fuel source for muscles during exercise. Our bodies use multiple energy systems to exercise. The type of energy system used depends on the exercise intensity and duration. At lower intensities, our bodies use a mix of both burning fat and carbs for fuel. When carbohydrate stores are low and/or hypoglycemia is present, it’s very difficult to exercise. Most studies involving endurance athletes showed the keto diet hurts their performance. Diet plus regular exercise is far more effective for long-term weight control than either one by itself.
- Potential heart health issues: There are mixed results in studies that examine the specific effects of the keto diet on heart health. This is likely because much of it depends on individual food choices.
- Possible negative effects on heart health: McManus recommends that you keep saturated fats to no more than 7% of your daily calories because of the link to heart disease.
- Kidney problems: The kidneys help metabolize protein, and McManus says the keto diet may overload them.
- Fuzzy thinking and mood swings: The brain works best when the energy source is sugar from healthy carbohydrates to function.
- Bone health concerns: There can be issues with bone health when people switch to low-carb keto diets. Researchers see that markers for bone breakdown are higher and markers for bone building are lower. A 2023 study (Corsello et al.) found that the diet may slow growth and reduce bone mineral density (BMD), particularly without careful monitoring, and emphasized starting preventive micronutrient supplementation from the beginning. A 2025 study (Bahbah et al.) of 56 children on KD for more than 2 years reported consistently lower bone density compared to healthy peers. However, outcomes were not worse than in children on anti-seizure medications alone, with ambulation and AED use proving stronger predictors of low bone density than the diet itself. Importantly, BMD reduction was seen across all groups-even with vitamin D and calcium supplementation-likely relating to less weight-bearing activity and underscoring the need for ongoing bone monitoring.
- Nutrient deficiencies: Research reviews show that KD can leave children short on several vitamins and minerals - particularly selenium, calcium, and B vitamins. Even with well-planned meals, these nutrients often fail to meet daily requirements without supplementation.
Long-Term Ketogenic Diet Therapy
Clinicians emphasized that, overall, side effects on long-term ketogenic diet therapy can be managed successfully. As one provider noted, “In our experience, side effects are usually easy to manage with appropriate follow-up care.” Another explained that while “we’ve occasionally seen vitamin deficiencies, these were mostly linked to poor supplement compliance.” A third clinician added perspective from years of practice: “Most side effects show up within the first year. With careful supplementation and monitoring, long-term keto doesn’t necessarily get harder over time.”
Making Informed Decisions about Keto
We gladly acknowledge that ketogenic diets have been shown to be helpful in treating severe epilepsy, and that a few people will be able to sustain their weight loss using this approach. Even for those dedicated few, long-term weight control will mean cycling in and out of ketosis. Unfortunately, more and more studies suggest that low-carb diets may actually increase your risk for all-cause mortality, as well as cardiovascular disease and cancer mortality. The best ketogenic diet for obesity is a dietary plan that you can enjoy for a lifetime. A short-term dietary change of any kind is ineffective for long-term weight management. Once we return to previous patterns of eating, weight regain is common and expected. Any dietary intervention that does not result in a lifelong change in eating patterns is destined to fail.
Before starting the keto diet, you should get a blood test to look at your lipids. Also, most people following a strict keto diet should take a multivitamin with minerals to ensure they're meeting those vitamin and mineral needs.
The Importance of Professional Guidance
The key to long-term KD success is working closely with your healthcare team. Neurologists and dietitians can help fine-tune the diet, monitor labs, adjust medications, and address side effects before they become bigger concerns. With their support, families can:
- Expect most side effects in the transitional period - these often improve as the body adapts.
- Know that digestive issues are the most common, both short- and long-term.
- Work with their healthcare team to adjust the KD ratio while still maintaining seizure control.
- Adhere to the supplement plan provided by your care team to help prevent deficiencies and side effects.
- Stay on top of labs to catch nutrient or metabolic issues early.
- Track growth and development by monitoring height, weight, and milestones.
Keto Diet Blogs
To overcome challenges like these, it’s apparent that what a keto dieter really needs is resourceful information and tons of encouragement. “One reason why the keto diet has continued to be popular is that it fosters a sense of community,” says Melissa Mitri, RD, the owner of Melissa Mitri Nutrition in Monroe, Connecticut.
Keto blogs can help you feel supported on the diet, which you'll need especially at the beginning, since it can be restrictive and for most people involves a totally new approach to eating. One thing to keep in mind, says Mitri, is that the authors of these blogs are not medical or nutrition experts but are speaking from their own experience. “Remember that everyone is different and there is no one diet that works for everyone,” she says.