The ketogenic (keto) diet, characterized by its high-fat, moderate-protein, and very low-carbohydrate composition, has gained considerable attention as a weight-loss strategy. Though it may seem newer, the ketogenic diet has been around since the 1920s. The keto diet is all about cutting carbs and eating more fat, similar to the Atkins diet from the 1970s. The diet aims to shift the body's primary fuel source from glucose to fat, inducing a metabolic state known as ketosis. In this state, the body breaks down fats into molecules called ketones. Ketones serve as an alternative fuel source. While some individuals report positive outcomes, it's crucial to understand both the potential benefits and risks associated with this dietary approach.
What is the Keto Diet?
The keto diet is all about cutting carbs and eating more fat. The ketogenic diet restricts carbohydrates to 50 grams per day or less. A more typical intake of carbohydrates is 150-250 grams, or three to five times as much. The keto diet is a high-fat, moderate protein, low-carbohydrate diet. Typically, carbohydrates in your diet provide most of the fuel your body needs. The keto diet reduces the number of carbs you eat and teaches your body to burn fat for fuel instead. The keto diet limits carbohydrates, forcing your body to burn fat for fuel instead. When these stores are full, they are converted into fat. The standard keto diet consists of 70% to 80% fats, 10% to 20% proteins and 5% to 10% carbohydrates. To achieve ketosis, the diet requires you eat 75 percent of your calories from fat, compared to 20-35 percent normally. It also requires 5 percent of calories from carbohydrates, about 20-50 grams per day, and 15 percent of calories from protein.
Achieving Ketosis
Ketosis is a metabolic adaptation to allow the body to survive in a period of famine. Ketosis, the cornerstone of the keto diet, is a metabolic state where the body primarily uses fat for energy instead of carbohydrates. Normally, the body uses blood sugar (glucose) as its key energy source. You typically get glucose in your diet by eating carbohydrates (carbs) such as starches and sugars. Your body breaks the carbohydrates down into glucose and then uses the glucose as fuel. Your liver stores the rest and releases it as needed. When your carb intake is very low, these glucose stores drain down. Since your body doesn’t have enough carbs to burn for energy, it burns fat instead. As your body breaks down fat, it produces a compound called ketones. The ketones, or ketone bodies, become your body and brain’s main source of energy. The fat your body uses to create ketones may come from your diet (nutritional ketosis), or it may come from your body’s fat stores. Your liver produces a small amount of ketones on its own. But when your glucose level decreases, your insulin level decreases. This causes your liver to ramp up the production of ketones to ensure it can provide enough energy for your brain. Therefore, your blood has high levels of ketones during ketosis. To achieve this, carb intake is drastically reduced, typically to less than 50 grams per day.
Foods to Eat and Avoid
People following the keto diet should be eating foods like fatty fish, eggs, dairy, meat, butter, oils, nuts, seeds and low-carb vegetables. People following the keto diet should be eating foods like fatty fish, eggs, dairy, meat, butter, oils, nuts, seeds and low-carb vegetables. “Fat bombs” like unsweetened chocolate or coconut oil can help people reach their daily goals for fat intake. The keto diet excludes carb-rich foods like grains, beans, fruits and starchy vegetables. All fruits are rich in carbs, but you can have certain fruits (usually berries) in small portions. Vegetables (also rich in carbs) are restricted to leafy greens (such as kale, Swiss chard, spinach), cauliflower, broccoli, Brussels sprouts, asparagus, bell peppers, onions, garlic, mushrooms, cucumber, celery, and summer squashes.
Potential Benefits of the Keto Diet
- “There has been anecdotal evidence of people losing weight on the ketogenic diet. People also report feeling less hungry than on other types of restricted diets,” says Melinda R. Ring, MD, director of Northwestern Medicine Osher Center for Integrative Health. Studies have found that individuals on a keto diet report less hunger and desire to eat. Research suggests that the keto diet helps people cut calories because the diet doesn't include many foods that people are likely to overeat.
Weight Loss
One of the biggest benefits of ketosis may be weight loss. The process can help you feel less hungry, which may lead to eating less food. The ketogenic diet (KD) has gained immense popularity during the last decade, primarily because of its successful short-term effect on weight loss. KD has been shown to effectively lead to weight loss, reduction in hyperinsulinemia, and improvement in insulin sensitivity.
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Epilepsy Management
The keto diet was first used as a treatment for pediatric drug-resistant epilepsy to reduce seizures in the 1920s. when medications alone aren't enough. Rachel Kleinman, RDN, LDN, clinical dietitian, says the keto diet is primarily used to manage seizures in children with epilepsy. Healthcare providers often put children with epilepsy on the keto diet to reduce or even prevent seizures by altering the “excitability” part of their brain. The keto diet has been used to help manage epilepsy, a disorder characterized by seizures, for more than 100 years.
Potential Benefits for Neurological Disorders
The keto diet is being studied for reducing symptoms for patients with progressive neurological disorders like Parkinson’s disease. But scientific research has not confirmed benefits for these patients, Dr. Ring says, and more research is needed before it can be widely recommended. Research has shown the keto diet may help improve neurological conditions such as Alzheimer’s disease, autism and brain cancers such as glioblastoma. The MIND diet can possibly help reduce the cognitive decline associated with aging.
Blood Sugar Control in Diabetes
Low carb diets like keto have been shown to help manage blood sugar levels in people with diabetes. The keto diet can help people with Type 2 diabetes lose weight and manage their blood sugar levels.
Improvement of Cardiovascular Risk Factors
The keto diet may lower your risk of developing cardiovascular disease by lowering your blood pressure, improving your HDL (“good”) cholesterol levels and lowering your triglycerides.
Potential Risks and Side Effects
- Because of the stringent food restrictions, many find the keto diet hard to stick to. “The ketogenic diet can be effective for weight loss when used in a short time period followed by the adoption of healthier eating habits,” says Baljash Singh Cheema, MD, a cardiologist at Northwestern Medicine Bluhm Cardiovascular Institute. “However, we know in studies of these types of diets that once people stop following that diet, they regain at least half of the weight that they lost. Ketosis is difficult to achieve because it’s like a light switch: either on or off. The keto diet is quite restrictive and hard to sustain long-term, making it not the best choice for lifelong weight management. Wellness dietitian Mary Condon, RN, LDN, says the keto diet may result in weight loss and lower blood sugars, but it’s a quick fix. “More often than not, it’s not sustainable. Strict diets like keto could also cause social isolation or disordered eating. Both Condon and Kleinman say they wouldn’t recommend the keto diet to their patients because it is ultimately not realistic or sustainable.
The "Keto Flu"
Carb intake on the keto diet is typically limited to fewer than 50 grams per day, which can come as a shock to your body (2). As your body depletes its carb stores and switches to using ketones and fat for fuel at the start of this eating pattern, you may experience flu-like symptoms. When people start the keto diet, they go through 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. One of the signs of ketosis may include “keto flu,” which includes symptoms such as upset stomach, headache and fatigue. Short-term health risks include flu-like symptoms, for example, upset stomach, headache, exhaustion and dizzy spells. Symptoms typically resolve after a few days to weeks as the body adjusts to the low CHO, ketogenic state.
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Nutrient Deficiencies
- “Because the keto diet is so restricted, you’re not receiving the nutrients - vitamins, minerals, fibers - that you get from fresh fruits, legumes, vegetables and whole grains,” says Dr. Ring. The keto diet is very low in carbs which means you can't eat many fruits and vegetables. Since the keto diet restricts several foods, especially nutrient-dense fruits, whole grains, and legumes, it may fail to provide recommended amounts of vitamins and minerals. The restricted nature of the keto diet can lead to inadequate intake of essential nutrients, including vitamins, minerals, and fiber.
Cardiovascular Concerns
- The high-fat nature of the diet could also have negative impacts on heart health. The American Heart Association recommends limiting saturated fat intake to less than 6%. McManus recommends that you keep saturated fats to no more than 7% of your daily calories because of the link to heart disease. “In practice, many people eat high amounts of saturated fats, which could increase your risk of heart disease,” says Dr. Cheema. “You may be eating a lot of fatty meat thinking it’s a good thing for you because it's high in fat. This can dramatically alter your lipid profile. While high-fat diets can elevate LDL (“bad”) cholesterol, the type of saturated fat matters. The bottom line is that having more fats in your diet can lead to higher cholesterol. “We know that higher cholesterol tends to increase your chances of heart attacks and strokes,” says Dr. Cheema. A considerable body of research has shown that diets high in saturated fat may increase the risk for heart disease and other chronic health problems. 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.
Kidney Problems
- The keto diet may not be appropriate for everyone, specifically people with kidney disease. “Although more research is needed in that area, there is some suggestion that it can make kidney disease worse over time,” says Dr. Some people also experience dehydration on the keto diet because they’re eliminating glycogen, which holds water, from the bloodstream. The kidneys help metabolize protein, and McManus says the keto diet may overload them. High fat animal foods, such as eggs, meat, and cheese, are staples of the keto diet because they don’t contain carbs. If you eat a lot of these foods, you may have a higher risk of kidney stones. Additionally, people with chronic kidney disease (CKD) should avoid keto, as weakened kidneys may be unable to remove the acid buildup in your blood that results from these animal foods. This can lead to a state of acidosis, which can worsen the progression of CKD. The keto diet could cause kidney stones, constipation, nutrient deficiencies and an increased risk of heart disease.
Psychological Effects
- When you micromanage your food intake by tracking how much you eat, it disconnects you from what your body is asking for. You start using outside numbers to determine what to eat instead of listening to your body. “Being intuitive and understanding what your body needs is essential for proper nourishment,” says Merneedi. Monitoring food so closely can lead to psychological distress, such as shame and binge eating. Strict diets like keto could also cause social isolation or disordered eating.
Blood Pressure and Blood Sugar Fluctuations
- The keto diet can cause your blood pressure to drop in the short term due to a reduction in blood volume and changes in your fluid balance. Following a keto diet can also cause your blood sugar to drop, which can be dangerous for people living with diabetes.
Constipation and Gut Health
Constipation is likely the greatest long-term complication of the keto diet because of a low fiber intake. Fiber is a form of carb that is digested not by our human cells, but by the microbes in our gut. The keto diet can lead to digestive discomfort and constipation.
Alternative Approaches
For long-term weight loss, Dr. Ring, Dr. Intermittent fasting is an approach that allows you to receive the benefits of ketosis while still eating a varied and balanced diet, says Dr. Ring. By cycling between periods of eating and fasting, your body enters “mild ketosis” during the fasting phase. “Unlike the keto diet, which requires strict food restrictions, intermittent fasting lets you enjoy a variety of nutrient-dense foods, such as fruits, vegetables, whole grains and legumes, during eating windows,” Dr. Ring explains.
Reduce, Don't Restrict, Carbohydrates
Reduction vs. A better choice when thinking about weight management would be to reduce the type of carbohydrates you eat rather than following the strict restriction of the keto diet. The priority should be to reduce simple carbohydrates and include more complex carbohydrates. Complex carbohydrates are high in nutrients and fiber that increase fullness, which can help with weight control.
Small, Consistent Changes
Dr. Cheema advocates making small changes based on your health goals. “People tend to burn out on those big goals and challenges, and then they go back into their own habits,” he explains. “Just because you were super fit between the ages of 36 and 38 may not extend your healthy life. But if you make small changes consistently every day from ages 36 to 66, that probably will have a big impact.
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