In this article
Editorial update: September 29, 2026. Text prepared with AI support from the indicated sources. No independent clinical review. General information, not an individual meal plan.
Short answer
Starting the ketogenic diet is, in practice, cutting almost all carbohydrates, keeping protein moderate, and making fat the base of meals. Before the first step, talk to a doctor or dietitian, especially if you have any illness, take medication, are pregnant, or are breastfeeding.
Step 1: talk to a doctor or dietitian
The Harvard Nutrition Source recommends consulting a doctor and dietitian before starting, to monitor changes in tests and adapt the plan to your health conditions. This is even more important for those who have any illness or take medication, and there are still doubts about the safety of keto in kidney and liver diseases and in pregnancy, breastfeeding, childhood, and adolescence.
Since the diet removes entire food groups, the dietitian can also design the plan to reduce the risk of missing nutrients. The points of attention are gathered in risks and precautions before starting.
Step 2: understand the carbohydrate limit
The ketogenic diet normally stays below 50 g of carbohydrates per day, and some versions go as low as 20 g. There is no “standard” version: popular materials suggest, on average, 70% to 80% of calories from fat, 5% to 10% from carbohydrates, and 10% to 20% from protein. In a 2,000 kcal diet, this amounts to about 165 g of fat, 40 g of carbohydrate, and 75 g of protein.
Protein is kept moderate for a concrete reason: in excess, it can prevent ketosis, because amino acids can be converted into glucose. Those who want to understand the logic of the diet before changing their plate can find the explanation in what is the ketogenic diet.
Step 3: build your plate
Think in three parts. Fat appears in all meals: olive oil and other vegetable oils, coconut oil, avocado, coconut, nuts (macadamia, walnuts, almonds, pecans) and seeds (sunflower, pumpkin, sesame, flax); butter and hard cheeses can be included. Protein comes from beef, poultry, pork, fish, eggs, or tofu. And volume comes from low-starch vegetables, such as leaves, broccoli, cauliflower, asparagus, bell pepper, mushrooms, and zucchini. Berries enter in small portions.
Walter Willett, professor at Harvard, notes that there are no long-term studies with people on keto and suggests favoring unsaturated fats (nuts, seeds, avocado, vegetable oils, and fatty fish) over saturated ones.
A simple day to start: scrambled eggs with hard cheese at breakfast; grilled chicken with greens, avocado, and olive oil at lunch; fish with broccoli in butter at dinner. To vary throughout the week, consult the list of allowed foods.
Step 4: know what leaves the menu
All versions of the diet cut carbohydrate-rich foods: bread, rice, pasta, cereals, cookies, and other grain and flour products; potato, corn, and other starchy vegetables; beans, lentils, peanuts, and other legumes; fruit juices, most fruits, and sugar, added or natural. Heavy cream, ice cream, and whole milk are also often restricted due to lactose. A 7-day meal plan shows how all this becomes a week of meals.
Step 5: prepare for the first days
With very little carbohydrate, the body first uses the glucose stored in the liver. If the restriction continues for 3 to 4 days and this reserve runs out, insulin drops and the body starts using fat as its main fuel, with the liver producing ketone bodies. More details about this phase are in how long it takes to enter ketosis.
During this period, hunger, fatigue, low mood, irritability, constipation, headache, and “brain fog” may appear, which can last from days to weeks. It does not happen to everyone, but it’s good to know beforehand and tell your doctor if the symptoms bother you.
Step 6: monitor and reassess
Coordinate with your doctor or dietitian how to monitor tests and when to reassess the plan. For long-term use, suggested negative effects include higher risk of kidney stones and osteoporosis and increased uric acid. When it’s time to return to eating more carbohydrates, the dietitian can also guide this return. And, if your doubt is what to expect from the scale, the text on results in 30 days gathers what the studies say.
Sources
- Harvard T.H. Chan School of Public Health, The Nutrition Source: Diet Review: Ketogenic Diet for Weight Loss
- Harvard T.H. Chan School of Public Health, The Nutrition Source: Emphasizing unsaturated fats on a ketogenic diet
Mariana is passionate about a healthy lifestyle.
