Wondering How Long It'll Take to Reach Ketosis? We Went to the Experts to Find Out

Whether you've tried the keto diet yourself, know people who have, or have seen incredible achievements from those who practice it, you've probably noticed that different people see different results at varying times after implementing it into their lives. While there are certain tips you can follow for making the keto diet work for you, there are still parts of the keto diet that are important to understand before diving into it.

On a keto diet, people drastically reduce their intake of carbs in order to reach a metabolic state called ketosis. When ketosis is reached, "it automatically acts as a mood elevator and natural appetite suppressant, as well as benefiting from the metabolic advantages you are using as your fat stores," Dr. Luiza Petre, board-certified cardiologist, told POPSUGAR.

Achieving a state of nutritional ketosis means that "your body will shift from burning carbs for energy to fats," which can be beneficial for improving glucose control, increasing energy, losing weight, improving mental clarity, feeling less hungry, and having fewer cravings, according to Dr. Catherine Metzgar, PhD, RD.

When you reach ketosis, "in the liver, fat turns into ketones, which [supply] energy for the brain," and once your body adjusts to burning fat as fuel, it will no longer be perceived as lacking energy, according to Dr. Petre. She added that "the end result is that it lowers insulin levels and blood sugar, shifting the metabolism to fat and ketones, and away from carbs," and eventually, your appetite will be balanced out with your body's energy needs.

In order to reach nutritional ketosis, "a person's macronutrient profile should be close to the following: 70 percent to 80 percent fat, 15 percent to 20 percent protein, and 5 percent to 10 percent carbs," Dr. Metzgar told POPSUGAR. Although this may seem like a large consumption of fats, eating healthy fats is one of the most important things to include when trying the keto diet. There are a variety of foods that you can add to your diet that contain the necessary amounts of fat, protein, and carbs to keep you both satiated and able to achieve results from trying the keto diet.

Because somewhere between 3/4 and 4/5 of your energy comes from fat when you're on the keto diet, Kristen Mancinelli, RD, and author of The Ketogenic Diet and the upcoming Jump Start Ketosis, told POPSUGAR that you'll be eating things like avocado, coconut, olive oil, animal fats, fatty fish, dairy, nonstarchy vegetables, nuts, seeds, leafy greens, and much more. Mancinelli recommends eating fattier cuts of meat like a chicken thigh with skin or pork belly instead of large portions of lean meats like chicken breast or lean steak because consuming too much protein can actually interfere with ketosis.

How long it takes to actually achieve ketosis, i.e., how long it'll take until your body is ready to run on fat, varies for each individual. However, most experts are in agreement that it will take anywhere from a couple days to two weeks.

The reason it can take some people as little as two days to achieve ketosis and others up to a couple weeks is because "for your entire life your body has been burning sugar for fuel. It will need time to adapt and burn off what you've stored," and factors such as "lifestyle, body size and type, activity level and carbohydrate intake, our unique metabolism, along with previous dieting history and varying resistance to insulin" all add to the variation of time it'll take to reach ketosis, said Dr. Petre.

Additionally, whether or not you've implemented the keto diet or intermittent fasting previously and what your diet currently looks like are also factors that will play a role in terms of how soon you'll reach ketosis, Mancinelli said. "Some people who have followed a ketogenic diet for a long time and then take a break can easily transition into ketosis in a day, whereas someone who [has] eaten a carb-heavy diet all their life may take quite a while to get through the initial change," said Mancinelli, and doing things like exercising will enhance metabolic flexibility, making your body "better at using fat for energy."

While some experts recommend not staying in ketosis over an extended period of time, others suggest staying in it as long as you can. It depends on you as an individual, including any previous or current health factors, which is why it's important to consult with your physician before implementing a new diet regimen.