A ketogenic diet shifts your body from burning carbohydrates for fuel to burning fat by drastically cutting carbs and replacing them with dietary fat. The standard breakdown is 70 to 80% of your daily calories from fat, 10 to 20% from protein, and just 5 to 10% from carbohydrates. For most people, that means eating somewhere between 20 and 50 grams of carbs per day. Here’s how to actually put that into practice.
What to Eat and What to Cut
The foundation of keto is unprocessed, whole foods that are high in fat and very low in carbs. Your plate will look different from a standard diet: avocados, eggs, fatty fish like salmon, nuts and nut butters, olive oil, butter, cheese, and non-starchy vegetables like leafy greens, broccoli, zucchini, and cauliflower. Meat, poultry, and seafood are staples. Dark chocolate (85% cacao or higher) and pork rinds work as snacks. Full-fat dairy, seeds, and coconut oil round out the fat sources.
What disappears from your diet is just as important. Bread, pasta, rice, cereal, potatoes, corn, most fruits, beans, and anything with added sugar all go. That includes obvious sweets but also less obvious sources: sauces, salad dressings, condiments, and flavored yogurts often contain corn syrup, cane sugar, honey, agave, or other sweeteners. The CDC notes that any ingredient ending in “-ose” (glucose, fructose, maltose, dextrose, sucrose) is a sugar. Words like “glazed,” “candied,” “caramelized,” or “frosted” on a label also signal added sugar.
How to Count Net Carbs
When people on keto say they eat “20 grams of carbs,” they usually mean net carbs, not total carbs. Net carbs are the carbohydrates your body actually absorbs. To calculate them, subtract fiber from total carbohydrates on a nutrition label. A cup of broccoli with 6 grams of total carbs and 2.4 grams of fiber, for example, has roughly 3.6 net carbs.
Sugar alcohols complicate this. If a product is sweetened with sugar alcohols like maltitol or xylitol, subtract only half of those carbs from the total, not all of them. Erythritol is the one exception: you can subtract its carbs entirely. This matters because some packaged “keto” products advertise very low net carb counts while using the full subtraction for all sugar alcohols, making the real number higher than what’s on the label. An Atkins bar listing 3 grams of net carbs, for instance, actually works out to about 8.5 grams when you apply the half-subtraction rule to its sugar alcohols.
What Happens in the First Week
Once you cut carbs to 20 to 50 grams per day, your body typically enters ketosis within two to four days. For some people it takes a week or longer, depending on factors like your previous diet, activity level, and metabolism. During this transition, your liver begins converting fat into molecules called ketones, which your brain and muscles use as their new primary fuel source.
The transition is not always comfortable. Many people experience what’s commonly called “keto flu” in the first few days to two weeks. Symptoms include headache, fatigue, upset stomach, constipation, insomnia, and irritability. You might also notice a distinct metallic or fruity taste in your mouth, often called “keto breath,” which is caused by your body exhaling a type of ketone called acetone. These symptoms are temporary and largely driven by dehydration and electrolyte loss, both of which are manageable.
Electrolytes Are the Key to Feeling Good
When you cut carbs, your kidneys flush out more water and, with it, critical minerals. This is the main reason keto flu hits so hard. Replacing those minerals proactively makes the transition dramatically easier.
The targets are higher than most people expect. A well-formulated ketogenic diet calls for 3,000 to 5,000 mg of sodium per day, 3,000 to 4,000 mg of potassium, and 300 to 500 mg of magnesium. For sodium, that means salting your food generously and drinking broth or bouillon. For potassium, leafy greens, avocados, and mushrooms help, though some people supplement. Magnesium-rich foods include nuts, seeds, and spinach, and a magnesium supplement before bed can also help with the insomnia some people experience early on.
Drink more water than you think you need. Dehydration is one of the most common early complaints, and it amplifies every other symptom.
Building Your Daily Meals
A practical day of keto eating doesn’t need to be complicated. Breakfast might be eggs scrambled in butter with spinach and cheese, or a coffee blended with coconut oil. Lunch could be a salad with grilled chicken, avocado, olive oil dressing, and a handful of nuts. Dinner might be salmon with roasted broccoli cooked in butter, or a burger patty (no bun) topped with cheese and served over greens.
Snacking becomes less necessary for most people because fat is highly satiating, but when you do snack, options include cheese, nuts, hard-boiled eggs, celery with almond butter, or olives. The goal is to hit your fat target without going over on carbs. Tracking your food in an app for the first few weeks helps you learn portion sizes and identify hidden carbs. Most people find they can stop tracking once they develop an intuitive sense for what fits.
Common Mistakes That Stall Progress
The most frequent mistake is eating too much protein and not enough fat. Your body can convert excess protein into glucose through a process that slows or prevents ketosis. Protein should make up a moderate portion of your diet, not the centerpiece. Think of your plate as fat-first, with protein as a supporting player and vegetables filling in the carb budget.
Another common pitfall is trusting “keto-friendly” packaged foods without reading labels carefully. Many of these products contain hidden sugars, misleading net carb counts, or enough sugar alcohols to spike blood sugar in sensitive individuals. Whole, single-ingredient foods are always the safest bet.
Undereating is also a trap. Some people combine keto with aggressive calorie restriction, which leads to fatigue, muscle loss, and eventually bingeing. Keto works partly because eating more fat keeps you full. Trying to go low-fat and low-carb at the same time defeats the purpose and feels miserable.
How to Know It’s Working
Beyond the obvious signs like reduced appetite and increased energy (which typically kick in after the first week or two), you can measure your ketone levels directly. Blood ketone meters are the most accurate option. Nutritional ketosis is defined as a blood ketone level of 0.5 to 3.0 mmol/L. Urine test strips are cheaper but less reliable, especially after the first few weeks when your body becomes more efficient at using ketones rather than excreting them.
Many people notice a natural drop in hunger, clearer mental focus, and more stable energy throughout the day once they’re fully adapted. Weight loss in the first week is largely water, which is normal and expected. Fat loss follows in subsequent weeks if you’re in a calorie deficit.
Who Should Be Cautious
Keto is not appropriate for everyone. Pregnant or breastfeeding women should avoid it entirely. People with heart failure, a recent heart attack or stroke, or those taking a class of diabetes medication called SGLT-2 inhibitors face serious risks from nutritional ketosis, including a dangerous condition called diabetic ketoacidosis. Anyone scheduled for surgery should stop keto beforehand and ensure they’re well hydrated.
There are also rare metabolic disorders involving the body’s ability to process fat for fuel. People with these conditions cannot safely produce ketones and could experience life-threatening complications. If you have any chronic health condition, especially involving your heart, kidneys, or metabolism, get medical guidance before starting.
For generally healthy people, the main long-term considerations are cholesterol changes (which can go in either direction on keto), bone density, and kidney stones. Staying hydrated, eating plenty of vegetables, and getting your electrolytes all reduce these risks substantially.