The ketogenic diet has come a long way from its humble beginnings.

Unless you’ve been living under a rock, you’ve probably heard of the ketogenic diet. You might have even tried it. This low-carbohydrate diet is high in fat and protein, which sounds scary, but it’s been shown to be effective as long as it’s followed correctly.

Initially developed in 1921 by Russel Wilder to treat epilepsy, this diet is now experiencing a resurgence. Celebrities like Gwyneth Paltrow, Lebron James, and Kim Kardashian have all gushed about the keto diet.

Like any plan that seriously reduces or completely cuts carbs, it’s not the easiest diet to stick to for a long period of time.

(Many people saw weight loss results in just their first week from following this “28-day Keto Challenge.”) Fortunately, you may not have to commit forever to reap the results.

We talked to experts to find out exactly how long you should follow the keto diet.

Remind me, what is the keto diet?

On the keto plan, your diet is composed of 70 percent fat, 25 percent protein, and 5 percent carbohydrates, says Samantha Lynch, R.D.N.

The goal of following a mostly fats diet is to put your body into ketosis. Studies show that it’s easy to get this wrong if you’re not following a proper plan. (Many have had success on this Keto plan here.)

When the body uses carbs as its primary source of fuel, it turns those carbs into a form of energy called glycogen. Ketosis slowly switches the body’s source of fuel from glycogen to ketones, thereby using fats as the body’s primary source of energy.

“When your body is relying on fat, there are a lot of ketone bodies—that’s the basic fuel source in the bloodstream—and the brain uses those very efficiently,” says Paul Salter, R.D., M.S., founder of Fit in Your Dress. As a result of this shift, the body enters a stage called ketosis. It now burns fat for fuel instead of carbs. The weight melts off quickly, and the results are often dramatic.

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How long does it take the body to get into ketosis?

Ketosis isn’t exactly easy to achieve. According to Salter, following the diet’s guidelines is paramount. This is because your body could snap out of its ketotic state at any point.

With the ketogenic diet, you have to meet these precise guidelines of eating—consuming this exorbitant amount of fat, a very small amount of carbohydrates—to actually see the benefits. If you do not eat to the guidelines, you actually don’t induce the state of ketosis to experience those benefits,” he says.

In order to see your body shift to ketosis and start experiencing benefits, you have to allow an adjustment period of a few weeks.

“The first two to six weeks are virtually the ketogenic adaptation phase, where your body is going through the adaptation of switching to relying primarily on fat versus glucose or carbohydrates,” Salter says.

He adds that to really see results, you should follow the diet for a minimum of three months.

Mark Sisson of The Daily Apple says there are four indicators that you’ve gone into ketosis:

1. Higher energy levels: Without carbohydrates, your body now has a “super fuel” that makes you feel more energetic.
2. No more cravings for sweets: Carbs are addictive, and if you’re eating them daily, you’ll continue to crave them. Once you eliminate them from your diet, you’re likely to find that you no longer desire them the way you once did.
3. “Keto breath”: You might notice a hint of metal on your breath, which is also described as a “sweet rotten apple” scent. It’s subtle and may not last long, but in the meantime, make sure you’re drinking plenty of water to flush out any odors.
4. Testing: To find out if you’ve entered ketosis, you can use urine test strips, a breath test, or a blood analysis.

What are some things to keep in mind while following the keto diet?

In order to achieve true ketosis and avoid any nutritional deficiencies, consult a registered dietitian or nutritionist prior to starting the keto diet.

It’s easy to develop an electrolyte imbalance while on the plan, Lynch says, as you are not allowed to consume many foods from which you gain electrolytes, such as certain grains, fruits, and vegetables.

Additionally, it’s important to pay attention to the kind of fat you consume.

“Because of the high amount of fat necessary, [the keto diet is] much more welcoming to all types of saturated and unsaturated fat,” Salter says.

Try to balance out your fat intake to include healthier fats as well. Lynch adds, “I think that people feel more satiated on a higher-fat diet. But it has to be done right and include healthy fats. Some healthy sources are avocado, olives, nuts, and fatty fish.”

So, how long should I follow the keto diet?

As is true for any diet, you should only begin to follow it if you can maintain it as a lifestyle change. All it takes is 28 days to see a huge transformation.

“If you want to keep the weight off, you’re going to have to eat well. You can’t go back to your old ways,” Lynch says. “A diet has an endpoint, and that’s the problem. With a lifestyle, there’s no end point. You have to put the work in.”

Salter echoes that sentiment, adding that there is no finite limit “as long as someone knows how to properly navigate carb-infested situations like social gatherings, vacations, and holidays, or [they] are OK with the ramifications if they do rapidly introduce carbohydrates in a short period of time. Any diet needs to be something that can you do and maintain for far longer. [The keto diet] certainly is. You just have to be diligent and educate yourself.”

How can I reincorporate carbohydrates into my diet?

It’s no secret that many people wind up gaining back the weight they lost as soon as they reincorporate certain foods.

“The vast majority of people who lose weight regain the weight they did lose within a year. So clearly we do have a weight maintenance problem,” Salter says.

He gives the example of someone lowering their daily calorie intake from 2000 to 1200. That person, he says, will lose weight but will not be able to sustain such a low-calorie intake.

“As a result, they’re going to give in to their hunger and the foods they’re craving and binge wildly, bringing their baseline calories up significantly,” he explains.

“If they can diligently and gradually bring their calories up by slowly introducing portions while simultaneously expanding their food selection, they can still maintain their weight loss and their health benefits, especially if exercise remains the focal point in their weekly regimen.”

Take it slow.

To add carbohydrates back into your diet, Salter advises starting off small. For example, start with one portion a day of 15 to 25 grams of high-fiber carbohydrates.

“Eat it either before or after exercise. That’s when your body is going to most efficiently use that carbohydrate source. It’s going to use it as fuel for your workout or replenish what your body burned during the workout,” he says.

He recommends following that pattern for five to ten days. Then, add the second portion to the opposite end of your workout as well. This way, you will consume a small number of carbohydrates both before and after your workout.

“Slowly move forward with that. Add a little more to the pre-workout. Add a little more to the post-workout meal,” he says.

“Once you get to a point where you’re comfortable with those meals, you can branch out. Add a little bit more to another meal of the day. It’s a very slow process. If you don’t slowly transition out of the ketogenic diet gradually, you’ll see the scale skyrocket. You’ll feel bloated and puffy, and that’s because there’s an overwhelming sensation of all these carbohydrates being returned.”

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How Long Is It Safe to Be in Ketosis?

In full transparency, there are no long-term studies on the ketogenic diet. An article out of Harvard Medical School says the early results on cardiovascular health are promising, but more extended research studies are needed.

Some people get thrown off by the “Keto Flu.” Don’t be fooled by the name. The Keto Flu isn’t a form of the flu. Instead, it’s a list of symptoms that resemble the flu. These symptoms sometimes occur when the body first goes into ketosis, but, according to Medical News Today, it’s not something you should be overly concerned about. Symptoms typically last a few days to a few weeks. (Consult with your doctor if you have any concerns).

For now, doctors tend to agree that as long as your bloodwork is at appropriate levels and your weight is within a healthy range, there’s nothing wrong with doing the keto diet long-term. Reading between the lines, we can tell you that ketosis is generally considered safe, but it’s not suitable for everyone. We recommend checking with your doctor before starting the ketogenic diet.

The biggest challenge you might face with the keto diet is sticking to it. With keto, there’s no such thing as a “cheat meal.” If you fall off the wagon and eat a donut or a bowl of pasta, you’ll fall out of ketosis – that fat-burning stage – and the process must begin again.

Just as important as your diet is your exercise program. To get the best results on the ketogenic diet, be sure to combine your eating plan with a fitness regime. Aaptiv features hundreds of workouts led by high-energy trainers. Sign up today for a free trial.