A keto diet shifts your body from burning carbohydrates to burning fat by drastically cutting carbs, typically to just 30 to 50 grams per day. The standard breakdown is 70 to 80% of your daily calories from fat, 10 to 20% from protein, and only 5 to 10% from carbohydrates. When you maintain those ratios consistently, your body enters a metabolic state called ketosis, where it produces molecules called ketones from stored fat and uses them for fuel instead of glucose.
What to Eat on Keto
The bulk of your plate comes from fat, which feels counterintuitive if you’ve spent years avoiding it. Good sources include olive oil, avocado oil, coconut oil, nuts (almonds, macadamia, walnuts, pistachios), and seeds like chia, flax, and pumpkin. Fatty fish such as tuna, mackerel, and sardines pull double duty by providing both fat and omega-3s. Butter, cheese (mozzarella, cheddar, blue cheese), and heavy cream are also staples.
For protein, stick with chicken, pork, beef, and eggs. You don’t need to eat enormous portions of protein. Too much can actually interfere with ketosis because your body can convert excess protein into glucose.
Vegetables are important, but you need to pick the right ones. Low-carb options include leafy greens, broccoli, cauliflower, spinach, mushrooms, bell peppers, asparagus, zucchini, eggplant, and radishes. Starchy vegetables like potatoes, corn, and sweet potatoes are off the table. Most fruit is too high in sugar, though small amounts of berries are generally fine.
The foods to avoid are obvious once you understand the carb limit: bread, pasta, rice, cereal, most baked goods, candy, soda, juice, beans, and most processed snacks. Even foods that seem healthy, like oatmeal or bananas, can blow through your daily carb budget in a single serving.
How to Count Net Carbs
Most people following keto track “net carbs” rather than total carbohydrates. The formula is simple: total carbs minus fiber minus sugar alcohols. Fiber and most sugar alcohols pass through your body without significantly raising blood sugar, so they don’t count against your limit. For example, a cup of broccoli might have 6 grams of total carbs but 2.4 grams of fiber, giving you about 3.6 net carbs.
This distinction matters because it opens up more vegetables and some low-carb packaged foods that would otherwise seem too high in carbs. Read nutrition labels carefully, though. Not all sugar alcohols are created equal, and some products use creative math to make their net carb counts look lower than they really are.
The First Week: Keto Flu
Most people feel noticeably worse before they feel better. Within the first day or two of cutting carbs, you may experience what’s commonly called “keto flu”: nausea, dizziness, muscle cramps, sugar cravings, brain fog, irritability, and trouble sleeping. Some people also get stomach pain, diarrhea, or constipation. For the average person this lasts about a week, though in some cases it can stretch to a month.
The main culprit is electrolyte loss. When you stop eating carbs, your body sheds water rapidly, and essential minerals go with it. You’re also cutting out some of the richest natural sources of electrolytes, like starchy fruits and vegetables. To minimize symptoms, focus on three things:
- Sodium: 3,000 to 5,000 mg per day. Salt your food generously, drink broth, or use electrolyte supplements.
- Potassium: 3,000 to 4,000 mg per day. Avocados, spinach, and mushrooms are good keto-friendly sources.
- Magnesium: 300 to 500 mg per day. Nuts, seeds, and dark leafy greens help, but a supplement is often easier.
These numbers are higher than what most people consume on a standard diet. Staying on top of electrolytes isn’t just a first-week strategy. It’s something you’ll need to maintain for as long as you eat keto.
How to Know You’re in Ketosis
Nutritional ketosis is defined as blood ketone levels between 0.5 and 3.0 mmol/L. You can measure this with a blood ketone meter (the most accurate option), urine test strips (cheaper but less reliable over time), or breath meters.
You’ll also notice some physical signs without testing. Many people experience a distinct metallic or fruity taste in their mouth, sometimes called “keto breath.” Appetite tends to drop noticeably once you’re in ketosis, which is one reason the diet can lead to weight loss. Some people also report improved mental clarity and more stable energy throughout the day, without the afternoon crashes that come from blood sugar swings.
Getting into ketosis typically takes two to four days of strict carb restriction, though it can take longer depending on your activity level, metabolism, and how drastically you cut carbs.
Three Versions of Keto
The standard ketogenic diet (SKD) is what most people mean when they say “keto.” You eat 30 to 50 grams of net carbs per day, every day, with no variation. This is the simplest approach and the one most beginners should start with.
The cyclical ketogenic diet (CKD) adds one or two higher-carb days per week, where you eat 100 to 150 grams of clean carbs. The other five or six days follow standard keto rules. This approach is popular with people who do intense exercise and find that strict keto limits their performance over time.
The targeted ketogenic diet (TKD) keeps your daily carb intake at the standard keto level but concentrates all of those carbs around your workouts, eating them before and after exercise. You stay in ketosis most of the day while giving your muscles quick fuel when they need it most.
If you’re new to keto, start with the standard version for at least a few weeks. You need to become fully adapted to burning fat before introducing carb cycling or targeted carbs, or you’ll just keep knocking yourself out of ketosis without ever getting the benefits.
Building a Typical Day of Meals
A practical keto day might look like this: eggs scrambled in butter with spinach and cheese for breakfast, a salad with grilled chicken, avocado, olive oil dressing, and walnuts for lunch, and salmon cooked in olive oil with roasted broccoli and cauliflower for dinner. Snacks might include a handful of macadamia nuts, cheese slices, or celery with a high-fat dip.
Meal prep helps enormously, especially in the first few weeks when you’re still learning which foods fit your macros. Cooking in batches and keeping keto-friendly snacks on hand prevents the moments where you’re hungry, nothing is ready, and the easiest option is a bowl of cereal. Many people find that tracking their food in an app for the first month builds an intuitive sense of portion sizes and carb counts that eventually makes tracking unnecessary.
Who Should Be Cautious
Keto changes how your body processes medications, particularly those for diabetes, epilepsy, and cardiovascular conditions. If you take any prescription drugs, especially insulin or blood sugar-lowering medications, adjusting your carbs this dramatically without medical guidance can be dangerous. Blood sugar can drop too low, or medication doses may need to change.
People with a history of gout may experience flares during the transition into ketosis. Those who’ve had their gallbladder removed often do better with a slower transition into high-fat eating rather than jumping in all at once. The risk of kidney stones is generally low on keto for most adults, though children on ketogenic diets for epilepsy (who are often on anti-seizure medication) have a higher risk.
Many of the listed contraindications for keto are based on a lack of studies in certain populations rather than clear evidence of harm. Still, if you have a complex medical history, working with a doctor who understands ketogenic diets specifically, not just one who’s heard of them, makes a meaningful difference in both safety and results.