You might be surprised to learn that you’ve probably gone into ketosis before, even if you weren’t on a ketogenic diet.
That’s because your body naturally goes into ketosis anytime it doesn’t have enough glucose for fuel[*].
No glucose from carbohydrates? Your body flips into ketosis and begins burning fatty acids as fuel instead.
But a ketogenic diet takes the metabolic state of ketosis to the next level. People who follow a low-carb or keto diet to get into a more permanent state of ketosis report health benefits like mental clarity, weight loss, and better performance at the gym.
But what is ketosis, exactly? How does it work and is it safe? What about for the long-term? Learn all of that and more is this complete guide to ketosis.
What is Ketosis?
Ketosis is the metabolic process of using fat as the primary source of energy instead of carbohydrates.
Carbohydrates fall into two categories:
- Starchy carbs from foods like bread, pasta, potatoes, and other high-carb vegetables
- Sugar from things like candy, cakes, pastries, and ice cream
On a higher-carb diet (or a Standard American Diet), the body runs almost exclusively off of glucose. You have glucose in your blood and stored glucose (aka, glycogen) in your muscles and organs like your liver.
On a low-carb or ketogenic diet, dietary fat and fatty acids from stored body fat are released into your bloodstream. From here, your body can use these fatty acids as fuel or they get transformed into molecules called ketones.
Ketones are produced when liberated fatty acids (from dietary fat and broken-down body fat) make their way to the liver. In the liver, they’re oxidized and turned into ketones to provide energy for your body and brain.
Fatty acids make great fuel, but ketones are even more powerful. Your body uses them efficiently as fuel. And ketones can cross the blood-brain barrier to provide quick energy for your brain. But only in the absence of glucose[*].
Health Benefits of Ketosis
Ketosis is one of the best-studied diets in the nutrition sciences. Its effects on physical performance and brain health is especially impressive. And, of course, many people use the keto diet to lose unwanted body fat while maintaining muscle mass.
Here are just a few known benefits of the keto diet:
Probably the most widely talked about use for ketosis right now is weight loss. Because you’re using fat as fuel, ketosis can help you burn through fat stores more quickly[*].
You may also shed more pounds while in ketosis because of its effects on blood sugar and insulin, cravings, and energy.
Blood Sugar Balance
Ketosis stabilizes blood sugar and helps prevent insulin resistance. Studies show that restricting your daily carbs may improve insulin sensitivity, obesity, and triglyceride levels[*][*]. In one study, insulin levels in the ketogenic group decreased three times more than the low-fat dieters[*].
Keeping blood sugar and insulin stable won’t just stave off metabolic syndrome and type 2 diabetes; it may also result in fewer cravings.
Another way ketosis helps you lose weight — you’ll have fewer cravings.
With keto, you can stop relying on your willpower and self-control muscle and instead rely on balanced hormones and naturally fewer cravings[*].
Keto can also suppress your appetite so you’re more satisfied with smaller portions[*].
Better Brain Health
Ketones can cross the blood-brain barrier and provide clean mental energy without the crash that comes with carb-heavy meals[*].
Although glucose is the preferred form of energy for the body, a large part of your brain can also ketones as fuel for mental performance on a low-carb ketogenic diet. Plus, your body can provide internally-made glucose to the brain (through gluconeogenesis) during ketosis.
Higher Athletic Performance
During long periods of exercise, the body uses both what you’ve recently eaten and stored glycogen to power you through. But when those glycogen stores have been used up and you still need fuel, the body must turn to protein or fat for more energy. This is not a very efficient process — unless the body has adapted to being in a ketogenic state.
When you’re in a ketogenic state, your body quickly converts dietary fat or stored fat into usable fatty acids or ketones for quick fuel.
Longevity and Disease Prevention
Blood glucose and insulin levels are directly related to brain health. So, it’s no wonder that many researchers are looking at ketosis as a treatment option for degenerative brain diseases like Alzheimer’s and dementia[*].
Ketosis can help balance blood sugar and make your cells more sensitive to insulin. Which is why many researchers are looking at a ketogenic as an alternative treatment for type 2 diabetes patients[*].
Cancer cells thrive off of glucose from carbs. So, there are some theories that getting into ketosis can help starve cancer cells and may be a good complementary therapy for cancer patients. Most studies on keto and cancer are done in animal models, but one 2007 study found that the ketogenic diet was helpful in managing brain cancer[*].
How to Get Into Ketosis
There’s only one real way to get into ketosis and that is to cut your carb consumption. The general carb limit for the keto diet is around 30 grams per day. If you’re an athlete, this may increase to 100 grams.
Of course, you’ll need to replace those calories from carbs with something else, and when it comes to a keto diet, that something else is protein and fat.
You’ll have a unique macronutrient ratio that works for your body and goals, but the general rule is:
- Carbs: 5-10% of daily calories
- Protein: 20-25% of daily calories
- Fat: 70-80% of daily calories
Use this keto macro calculator to find the macros that work for you. Other than your macros, it just takes a little time to become fat-adapted. Fat-adaptation simply means that you’ve run through your stored glucose and your body is now used to running off of fatty acids and ketones.
Here’s how it works:
Step #1: Cut Carbs
When there isn’t a sufficient level of available glucose and glycogen levels are depleted, blood sugar and insulin levels decrease, and the body looks for an alternative source of fuel (fat).
Step #2: Your Body Breaks Down Fatty Acids
The body breaks down fats for energy. This process is known as beta-oxidation, where there is an increase in acetyl-CoA, which turns into acetoacetate. Acetoacetate then shifts to beta-hydroxybutyrate, the ketone body that floats around in your blood to then provide energy to the body and brain.
Step #3: Using Ketones
Your body and brain are able to use ketones as a quick and efficient source of fuel.
How Many Carbs For Ketosis?
The number of carbs you have to cut to get into ketosis varies from person to person. This depends heavily on:
- How much fat you have to lose
- Your activity level
- Your metabolism
Many people have to cut down to 30 grams of carbs per day or fewer to start the fat-adaptation phase. Others — like athletes who burn a lot of energy throughout the day — can get away with more carbs, from 50-80 grams.
Again, use the keto macro calculator to determine your carb goals. If you’ve gone three to four weeks on a keto diet and you’re still not in ketosis, you may want to lower your carb intake even more.
If you’re super low on energy after the first week or so on a keto diet, you may want to add some carbs back in.
How Long Does It Take to Get Into Ketosis?
This transition could take anywhere from 48 hours to one week, depending upon your activity level, lifestyle, body type, and carbohydrate intake. It also depends on whether or not you’ve become fat adapted before.
Many people report being able to get back into ketosis quickly once they have been in ketosis prior.
There are several ways you can speed up this process, like intermittent fasting, drastically cutting your carb intake, trying a carnivore diet, or cutting carbs while upping your exercise routine to burn through stored glucose faster.
How to Get Into Ketosis in 24-Hours
The average person may enter a mild state of ketosis during an overnight fast. Fasting causes your blood sugar and insulin levels to drop. These metabolic changes signal your liver to turn fatty acids into ketones[*].
But that doesn’t mean that you’re fat-adapted or that you’ll get the benefits of ketosis overnight.
It’s highly unlikely you’ll get into a steady state of ketosis in 24 hours. Even more so if you’re doing a ketogenic diet for the first time. Your body has been burning sugar for fuel your entire life. It will need time to adapt to burning ketones for fuel.
And remember: Once you get into ketosis, there is no guarantee you will remain in ketosis. If you eat a carb-laden meal, practice carb cycling, or increase your carb intake for athletic performance, your body may start burning glucose again.
To get back into a fat-burning state, follow the same methods you did to get into ketosis initially.
How to Stay in Ketosis
Staying in ketosis is pretty simple. Just continue restricting carbohydrates and focusing on low-carb vegetables, high-quality protein, and healthy fats like grass-fed butter and coconut oil.
Other tips to stay in ketosis include:
- Intermittent fasting
- Make sure you’re not overeating calories
- Commit to a fitness plan to keep your glycogen stores low
How to Tell if You’re in Ketosis
You might be wondering, what does ketosis feel like? Do you have to test your ketone levels to know whether or not you’re in ketosis?
The first phase of ketosis is actually called the fat-adaptation phase or keto-adaptation phase.
This is when you’re making ketones, but your body isn’t 100% used to producing them or using them as fuel.
When you begin to produce ketones on a more regular basis, you’re fat-adapted. Your body has fully shifted over to burning fat as its primary fuel source, to the point where you have metabolic flexibility: you can eat carbs and fall out of ketosis, and your body will snap right back into keto once it processes the carbs. This may take a month or more.
During this adaptation phase, many people experience flu-like symptoms that include:
- Brain fog
- Dizziness or confusion
- Diarrhea or constipation
- Muscle cramping or soreness
- Lack of concentration or focus
- Trouble falling or staying asleep
- Sugar cravings
- Heart palpitations
These symptoms are temporary and should subside in a week or two.
Getting into ketosis — even on the keto diet — does not guarantee fat-adaptation. That’s why it’s important to stick to strict keto for at least a few weeks when you’re just starting out if you want all the biggest benefits of ketosis.
Once you’re fat-adapted and in ketosis — that’s when you can really tell you’re in ketosis.
What does Ketosis Feel Like?
Many people report feeling differently when they’re in ketosis. A few noticeable side effects of ketosis include:
- More stable energy
- Reduced cravings
- Mental clarity
- More endurance
- Weight loss
Still not sure you’re in ketosis? You may want to test.
How to Measure Your Ketone Levels
A great way to be sure you’re in ketosis is by measuring the ketone levels in your body, and you can do this right from home.
When your body makes ketones, it won’t use all of them all as energy.
Excess ketones will spill into different areas of the body. There are three different ways you can measure ketone bodies: in your urine, blood, or breath.
You can use a blood glucose meter to test for levels of the ketone BHB. Since there are very few factors that alter results found through this method, it’s an accurate way to measure levels. It is more pricy, however, at about $5-$10 for each test strip.
Use a urine strip. Package instructions might vary slightly, but generally, after around 45-60 seconds you should be able to see the color that indicates the measure of ketones in your urine.
This is the least expensive testing option, but the least reliable. Your body becomes efficient at using ketones when you’ve been in ketosis for a while, so the strips might show a lower level of ketosis than you’re actually in.
Plus, other variables like hydration level and electrolyte levels can change the readings. So it’s better to use this method if you’re brand new to ketosis.
This method is best used as a supplement to a blood or urine test to help confirm ketone levels. You can use a Ketonix meter to test breath acetone, or BrAce, levels. The advantage of this method is that you can purchase a meter once and used as many times as needed — no strips required.
Is Ketosis Safe? What Are The Long-Term Effects?
A state of ketosis is 100% safe. In fact, low-carbohydrate diets help people to shed unwanted fat, avoid metabolic disease, and perform better at work and at the gym.
When this question comes up, most people are thinking of a few different things:
- High-fat diets will kill you
- That ketosis is starving the body of important nutrients
- Ketosis is actually ketoacidosis, which is much different
Luckily, none of these things are true.
Ketosis Does Not Cause Heart Disease
We’ve all been told that fat, especially saturated fat and dietary cholesterol, cause hardening of the arteries and heart disease. This is simply not true based on the latest research.
Ketosis Won’t Starve You of Micronutrients
If you do keto wrong, you may end up deficient in certain vitamins and minerals. But do keto correctly, eat real, whole foods, and you shouldn’t have a problem.
The fact is: meat, vegetables, and healthy fats are the most nutrient-dense food groups on the planet. High-sugar fruits and grains pale in comparison.
Ketosis vs. Ketoacidosis
People also often confuse ketosis with diabetic ketoacidosis (or DKA). But they are two different things entirely.
DKA occurs when the amount of ketones in the blood is extremely high and can turn the blood acidic. Diabetics can get DKA if they don’t take enough insulin, become dehydrated from not drinking enough fluids, or become hurt or sick. Other causes may be starvation, alcoholism, or an overactive thyroid.
Symptoms of DKA may include:
- Nausea or vomiting
- Excessive urination or thirst
- Fruity-smelling breath
- Gasping or breathlessness
Ketoacidosis is a dangerous state that can be deadly if not treated, and it’s not the same as nutritional ketosis — that we’re talking about here — which is a safe state achieved through a healthy low-carb diet.
Ketosis is a normal metabolic function in which your body is using ketones efficiently and safely. When you adopt a keto diet, you’ll only produce a low level of them in your blood. Enough to give you energy — not nearly enough to harm you.
How Long is it Safe To Be in Ketosis?
Low-carb, high-fat diets are far from dangerous in the short-term. What about over years or decades?
To date, there isn’t much research showing the long-term effects of a ketogenic diet over the course of several years. But there’s no research to suggest that long-term keto is bad for you, either.
- Blood glucose
- Blood pressure
If your body didn’t like ketones, it’s highly unlikely you’d see so many positive side effects.