How do I start a keto diet and achieve nutritional ketosis?

To start a ketogenic diet and achieve nutritional ketosis, follow these steps:

1. Understand the Basics: Educate yourself about the ketogenic diet. The primary goal is to shift your body's metabolism from using carbohydrates for energy to using fats. This metabolic state is known as ketosis. 
2. Calculate Your Macronutrient Ratios: Determine your daily macronutrient ratios, which are the amounts of carbohydrates, fats, and proteins you should consume. Generally, a standard keto diet involves consuming 70-75% of calories from fat, 20-25% from protein, and only 5-10% from carbohydrates.
3. Limit Carbohydrate Intake: Restrict your carbohydrate intake to a maximum of 20-50 grams per day, depending on your body and activity level. This restriction is essential to deplete your glycogen stores and prompt your body to enter ketosis.
4. Choose Healthy Fats: Include healthy sources of fat in your diet, such as avocados, nuts and seeds, olive oil, coconut oil, grass-fed butter, and fatty cuts of meat. These fats will provide energy and help you feel satiated.
5. Moderate Protein Intake: Consume an adequate amount of protein, but avoid excessive protein intake as it can interfere with ketosis. Good sources of protein include eggs, fish, poultry, grass-fed meats, and vegetarian options like tofu and tempeh.
6. Include Low-Carb Vegetables: Incorporate non-starchy vegetables with low carbohydrate content into your meals. Examples include leafy greens, broccoli, cauliflower, zucchini, peppers, and asparagus. These vegetables are high in fiber and nutrients.
7. Stay Hydrated: Drink plenty of water throughout the day to stay hydrated. Ketosis can cause increased water loss, so it's important to replenish fluids regularly.
8. Avoid Processed Foods and Sugars: Eliminate processed foods, sugary drinks, grains, and legumes from your diet. These foods are high in carbohydrates and can hinder ketosis.
9. Monitor Ketone Levels: Use ketone testing strips or a blood ketone meter to monitor your ketone levels. This will help you ensure that you're in ketosis.
10. Be Patient and Persistent: It may take a few days or weeks for your body to adapt and enter ketosis. Be patient, and stay consistent with your diet to achieve and maintain nutritional ketosis.

Remember, it's always a good idea to consult with a healthcare professional or a registered dietitian before starting any new diet, especially if you have any underlying health conditions. They can provide personalized guidance and support.