This Is How Long It Takes the Keto Diet to Work

Updated: Feb. 01, 2021

The average time isn't as long as you think.

Keto diet food ingredientsGeorge Dolgikh/Shutterstock

The ketogenic “keto” diet promises significant results for what’s a big change in the way you eat. The high-fat, moderate-protein, low-carb diet promises to burn body fat, and it’s different from the average American diet. Keto may not be the easiest eating plan, but it doesn’t take too long to see results—depending on your goals.

First, you have to understand what happens to the body during the keto diet. The eating plan aims to put your body into ketosis, meaning you burn fats as a primary fuel source instead of the glucose found in carbohydrates, says Robert Santos-Prowse, RD, a clinical dietitian, and author of The Ketogenic Mediterranean Diet and The Cyclical Ketogenic Diet. How does that work? “Ketones are created as a byproduct of the chemical reactions your body performs to break fat down,” Santos-Prowse says. “These ketones are then used by almost every cell in the body as fuel.” Find out which 12 keto supplements can make your transition easier.

To get to ketosis, you have to deprive your body of glucose and restrict the carbs in your diet. Most people probably need to limit their carb intake to 25 to 30 grams total per day to get into ketosis, Santos-Prowse says. This process takes about three days for most people, but in some cases it can take up to a week, depending on your genes, how much muscle you have, your insulin sensitivity, your activity level, and of course, your prior diet. Natalie Allen, RD, an instructor of biomedical sciences at Missouri State University, adds that the lower your carb intake, the quicker you’ll produce ketones. Some people can have as many as 50 grams of carbs per day and still be in ketosis, she says. 

If your main keto diet goal is weight loss, the level of ketosis you achieve isn’t that important, says Santos-Prowse. As long as you are restricting your carbohydrate intake to 25 to 30 grams and mind your portions, you’ll see results. You’ll see an immediate drop in water weight, plus consistent fat loss as you progress. For people on the diet for athletic performance or cognitive benefits, it could take anywhere from a week to a couple of months to see those results, says Santos-Prowse. Just watch out for these 10 ways the keto diet can backfire.

Although there are many keto diet benefits—like losing weight, feeling fuller, and maintaining muscle mass—Allen says it’s a challenging diet for people to follow the right way. “Remember, the body needs some calories, so make sure to eat meats, non-starchy vegetables, fats, and nuts,” she says. Plan ahead, learn how to cook proper meals, include veggies, and don’t forget to drink lots of water. Allen also suggests meeting with a dietitian to make sure you’re getting the proper amounts of vitamins and minerals and to avoid making these 13 common keto diet mistakes.

Still, other dietitians don’t think the keto diet works long-term at all. A recent U.S. News & World Report ranking the best diets didn’t give keto very high marks. Dietitians determine gave it a score of two out of five, making it the 38th best out of 50 other diets. Sade Meeks, RD, a Barley+ registered dietitian, is one of many who doesn’t recommend keto for sustainable, long-term weight loss. “Diets tend to focus on the ‘macros,’ but key micronutrients should not be overlooked,” she says. If you do decide to try the keto diet, check out this easy keto diet menu for beginners.