What Is the Keto Diet? Everything a Doctor Wants You to Know

The ketogenic diet is a high-fat, low-carbohydrate diet that severely restricts carbohydrate intake while focusing on fats and proteins. The key principle is to put your body into a state of ketosis, where it uses fat as the primary energy source instead of carbohydrates. This diet offers various health benefits including blood sugar control, enhanced immunity, improved digestion, and better sleep quality, with proper intake of essential nutrients like antioxidants and magnesium being crucial.

What is the Ketogenic Diet?

The ketogenic diet was first introduced in the medical field in the 1920s for treating epilepsy. In this diet, 70–75% of daily calories come from fat, 20–25% from protein, and only 5–10% from carbohydrates. Unlike typical low-carb diets, the keto diet restricts carbohydrates to 20–50 grams per day or less.

When the body becomes deficient in glucose, the liver breaks down fat to produce ketone bodies. The state in which these ketone bodies become the primary fuel for the brain and muscles is called ketosis. Generally, you enter ketosis within 3–7 days of starting carbohydrate restriction, with the state becoming established when blood ketone levels reach 0.5 mmol/L or higher.

Allowed foods on the keto diet include eggs, fish, meat, cheese, butter, nuts, olive oil, avocado, and low-carb vegetables (spinach, broccoli, cabbage). Conversely, grains, sugar, fruits (except berries), and some dairy products are restricted.

Benefits of the Keto Diet

Blood sugar control and improved insulin sensitivity are the most noteworthy benefits of the keto diet. According to research, a group that followed the keto diet for three months saw an average 28% decrease in blood sugar levels, with improved insulin resistance as well. This is particularly effective for managing type 2 diabetes.

Improved digestion occurs because protein and fat provide longer-lasting satiety than carbohydrates. Many users report regular bowel movements and reduced abdominal bloating. However, constipation may occur initially, so adequate water intake and dietary fiber (low-carb vegetables) are essential.

Improved sleep quality results from stabilized brain waves during ketosis. As blood sugar fluctuations decrease, sleep interruptions due to nocturnal hypoglycemia diminish, and the proportion of deep sleep increases.

Enhanced immunity is related to the anti-inflammatory properties of ketone bodies. Ketones inhibit the NF-κB signaling pathway to reduce inflammation and improve white blood cell function. Additionally, through antioxidant action, they prevent cell damage and eliminate reactive oxygen species (ROS).

Stress reduction is a secondary benefit resulting from blood sugar stabilization and stable brain energy supply. When blood sugar spikes and crashes are not repeated, cortisol levels also remain within normal ranges.

What are Macronutrients?

Macronutrients are the three major nutrients your body requires in large quantities: carbohydrates, protein, and fat. The keto diet restructures the ratios of these nutrients.

Protein intake is recommended at 1.2–2.0 grams per kilogram of body weight per day. In the keto diet, protein plays a key role in preventing muscle loss, maintaining satiety, and boosting metabolism. Excessive protein intake (2.5 grams or more per kilogram of body weight per day) can convert some protein to glucose, which may interfere with ketosis, so caution is needed.

Fat is the primary energy source in the keto diet, accounting for 70–75% of daily calories. Balanced intake of saturated fat, monounsaturated fat, and polyunsaturated fat is important. MCT (medium-chain triglyceride) oil is rapidly absorbed and is effective in promoting ketosis.

Magnesium is often overlooked as a micronutrient, but it's particularly important in the keto diet. As the body enters ketosis, water and electrolyte loss increases, and magnesium deficiency can cause muscle cramps, fatigue, and headaches. The recommended daily intake is 400–420mg for adult males and 310–320mg for females.

Sugar is the Problem

Sugar is the biggest enemy of the keto diet. Sugar, which rapidly breaks down into glucose and fructose, causes insulin spikes that immediately remove your body from ketosis. Even small amounts of sugar (5–10 grams) can lower blood ketone levels.

What's more problematic is sugar's addictive nature. Sugar stimulates dopamine release, causing a brain response similar to cocaine. According to research, high sugar consumption impairs the function of the hippocampus (memory center) and increases inflammation, weakening immunity. Chronic sugar consumption continuously elevates cortisol, a stress hormone.

When starting the keto diet, you may experience sugar withdrawal symptoms (headaches, fatigue, irritability) for the first 1–2 weeks. This is the process of your body breaking free from glucose dependence and is a normal phenomenon. Artificial sweeteners (aspartame, sucralose) should be completely avoided, and natural sweeteners like erythritol or stevia can be used as replacements.

How Does the Keto Diet Work?

The keto diet works by switching your body's energy metabolism system. In a normal state, your body converts glucose extracted from carbohydrates into ATP (energy molecules) for use. However, when carbohydrates become scarce, your body mobilizes stored fat.

In the liver, fatty acids are broken down to produce acetyl-CoA, which is then converted to ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone). These ketone bodies travel through the bloodstream to reach the brain, muscles, and heart, where they are used as energy sources instead of glucose. The brain can obtain up to 60% of its total energy consumption from ketone bodies.

Through this process, body fat continuously decreases. This is because hormone-sensitive lipase in fat cells is activated to break down stored triglycerides. At the same time, as insulin levels drop, ghrelin, the hormone that stimulates appetite, decreases, while leptin and CCK hormones that induce satiety increase. As a result, natural calorie restriction occurs.

Interestingly, the resting metabolic rate during ketosis actually shows little significant change. Instead, the thermic effect of food and automatic calorie restriction due to satiety are the main mechanisms for weight loss. According to research, those following the keto diet recorded an additional average weight loss of 13 kilograms compared to a low-fat diet control group after six months.

Supplements for the Ketogenic Diet

To safely follow the keto diet, certain supplements are essential. Since the body rapidly loses water and electrolytes, electrolyte supplementation is the top priority. Adequate intake of sodium (3,000–4,000mg/day), potassium (3,500–4,700mg/day), and magnesium (400mg/day) is essential. Deficiency can result in "keto flu" symptoms (headaches, fatigue, muscle cramps).

Magnesium requires special attention. The magnesium contained in vegetables consumed on the keto diet (spinach, broccoli) may not be sufficient, so consider a magnesium glycinate supplement (400mg/day). This form has superior absorption rates and causes less digestive stimulation.

Omega-3 fatty acid supplementation (fish oil or algae-based) reduces inflammation and enhances antioxidant effects. One daily serving based on 500mg EPA and 500mg DHA is appropriate.

Vitamin D is important for calcium absorption and immune function during ketosis. If sun exposure is insufficient, supplementation of 2,000 IU/day is recommended.

MCT oil is optional but increases the speed of ketosis induction and improves energy levels. Start with a small amount (5–10ml) and gradually increase. Excessive intake can cause digestive discomfort.

Medical professional consultation: If you have underlying health conditions (diabetes, heart disease, kidney disease) or are taking medications, be sure to consult with a doctor or nutritionist before starting the keto diet. Especially for diabetic patients undergoing insulin therapy, there is risk from rapid changes in blood sugar levels.

Conclusion and Key Points

The keto diet goes beyond being a simple weight loss method and serves as a comprehensive health management tool offering blood sugar control, improved digestion, better sleep quality, enhanced immunity, and antioxidant and anti-inflammatory benefits. The key is to severely restrict carbohydrates (20–50 grams daily) to induce your body into ketosis, and maintaining the proper ratio of fat and protein (70–75% fat, 20–25% protein) is important throughout this process.

Key factors for success include complete elimination of sugar, adequate protein intake (1.2–2.0 grams per kilogram of body weight), magnesium and electrolyte supplementation, and consumption of antioxidant-rich low-carb vegetables. Initial withdrawal symptoms during the first 1–2 weeks are normal and will disappear with persistence.

The effects of the keto diet vary greatly among individuals, so it's wise to monitor through regular blood tests (blood sugar, insulin, blood ketones, lipid levels). Always consult with a healthcare professional before starting, and especially those with chronic conditions or taking medications must proceed under a doctor's guidance. When properly implemented, the keto diet can result in noticeable health improvements and increased energy levels within 3–6 months.