Ketosis Guide: Symptoms, Benefits, and Safety Tips

Ketosis: Symptoms, Benefits, Risks, and More

Ketosis: Symptoms, Benefits, Risks, and More
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If you research different ways to lose weight, you’ll come across various diets and lifestyle tweaks to help your body burn fat more efficiently. Increasing the intensity and frequency of your exercise routine and adjusting the number of calories you consume daily are popular methods for reducing body fat. Another involves entering a metabolic state called ketosis, which is the mechanism behind many low-carb diets, including the ketogenic diet and the Atkins diet.

Understanding ketosis and how to achieve it can yield impressive short-term fat-burning results. Some people eat to enter ketosis so they can manage medical conditions, such as epilepsy and type 2 diabetes, and reduce their risk of others, like metabolic disease and heart disease. But cutting carbs is challenging to maintain over the long term, may have side effects including constipation and fruity-smelling breath, and can be dangerous for some people.

Before you attempt to achieve ketosis, you should know a few things about the process, including its potential benefits, risks, and how to approach it safely.

What Is Ketosis, and How Does It Affect Weight Loss?

Ketosis happens when your carbohydrate intake is low. As your liver breaks down fat, it produces acids called ketones or ketone bodies. These become your body and brain’s main source of energy.

Three main nutrients in foods supply your body with this energy: carbohydrates, fat, and protein. Your cells’ main energy source is glucose, a sugar you get from carbohydrates in food, but which your brain can’t store. If you fast or don’t eat many carbohydrates, your body uses glucose that’s stored in the liver.

Once this supply runs out — usually after three to four days — levels of insulin, a hormone that “unlocks” cells to let them use glucose as fuel, drop. The body then starts to use its fat stores, with the liver turning stored fat into an acid called ketones that it can use for energy.

The buildup of ketones, or ketone bodies, is known as ketosis.

Because ketosis shifts your metabolism and relies on fat for energy, your body can burn fat at a higher rate.

How Do You Achieve Ketosis Successfully?

Putting your body in ketosis can be challenging, to say nothing of staying in the state long-term.

Limiting Carb Intake

You’ll need to severely limit your carbohydrate intake. Only about 5 to 10 percent of your daily calorie intake should come from carbs, meaning you’ll be eating no more than 20 to 50 grams (g) of carbs per day to achieve and maintain ketosis.

This can be highly restrictive. A single medium (178 g) pear, for example, contains 27.1 g of carbs, which is more than some people’s daily limit on keto.

And even foods that aren’t generally considered high in carbs — such as nuts and nonstarchy veggies — contain small amounts of certain types of carbohydrates.

If you’re planning to enter ketosis, you’ll need to be aware of even the most minimal carb content and limit your intake once you’ve hit your daily intake.

Limiting Protein Intake

If you’re following the keto diet, you will need protein, which should account for about 10 to 20 percent of your total daily calories.

This is a key part of achieving ketosis. When you consume more protein than you need, your body converts the excess protein into carbs through a process called gluconeogenesis. This process pushes your body out of ketosis. Research has found that consuming 2.1 g of protein per kilogram of body weight lets you stay in ketosis while keeping your protein intake steady.

Intermittent Fasting

Another popular dietary approach is called intermittent fasting, which is based on skipping food for limited, planned periods of time and only eating during specific windows. Intermittent fasting will not put you into ketosis on its own, but some people combine intermittent fasting with a keto diet.

Limited research suggests that this might help you reach ketosis more quickly.

 A randomized, controlled trial found that although both a keto diet and intermittent fasting significantly reduced body weight and fat mass, combining them had the most pronounced weight and fat loss effects.

This combination approach hasn’t been studied or proven to work for long-term weight loss, however, and the pool of research supporting it is very small. Each of these diets can be challenging to maintain alone, and combining them may make it even more difficult to stick to your plan.

Exogenous Ketones

Some people take supplements, such as exogenous ketones, to put their body in ketosis and help keep it there.

However, it’s worth noting that more long-term research on humans is necessary before researchers can recommend these supplements as a standard therapy. They have shown positive effects on blood sugar control, heart function, cognitive, and immune support, but only in limited studies.

Exogenous ketones are also pricey, foul-tasting, can cause gastrointestinal symptoms due to their high mineral loads, and are awash in marketing that makes overambitious or scientifically unsupported claims about performance improvement, weight loss, and mental clarity.

How Do You Know You’re in Ketosis?

Checking your ketone level is one way to know if you’re in ketosis.

This metabolic state usually kicks in after three or four days of restricting your carbohydrate intake. You don’t have to visit a doctor to measure your level. Pick up a ketone urine test from a nearby drug store, or use a blood sugar meter that’s capable of measuring ketones.

A normal blood ketone level is less than 0.6 millimoles per liter (mmol/L).

Any level higher than this can indicate a state of ketosis.
You may start to lose weight or feel less hungry as you enter ketosis. It also causes several symptoms as your body adjusts. People often refer to this as the “keto flu.” Experts say the symptoms should subside within two weeks. Physical signs and symptoms of ketosis include:

  • Upset stomach
  • Headache
  • Fatigue
  • Brain fog
  • Irritability when hungry

  • Muscle cramps

  • Fruity-smelling breath
  • Tiredness that gets better after a few days
  • Constipation or diarrhea
These symptoms may feel better after a couple of days, or you may have them for as long as a month.

The Relationship Between Ketosis and the Ketogenic Diet

Following a keto diet — a very low-carb, high-fat diet — focuses on replacing carbohydrates with healthy fats, while purposely forcing the body into ketosis for weight loss. Keep in mind that this diet doesn’t just focus on eating fewer carbs. It also focuses on eating more whole foods and fewer processed foods.

With this diet:

  • 70 to 80 percent of your daily calories come from fat
  • 10 to 20 percent come from protein
  • 5 to 10 percent come from carbohydrates

Following a typical keto diet food list, you can eat certain foods freely, while you’ll need to limit or totally avoid other foods.

Foods to eat on the keto diet include:

  • Meat, including beef, lamb, pork, poultry, fish, and seafood
  • Eggs
  • Dairy and unsweetened dairy alternatives, including full-fat cheese, plain, full-fat yogurt, cottage cheese, and unsweetened plant milks
  • Healthy oils, such as olive oil, avocado oil, or coconut oil
  • Avocados
  • Low-carb, nonstarchy vegetables, like leafy greens, broccoli, and peppers
  • Nuts and seeds
  • Sometimes, berries
Foods to avoid on the keto diet include:

  • Grains, such as rice and quinoa
  • Foods made from grains, such as pasta, rice, bread, and pizza
  • Foods high in added sugar, including sweets, many fizzy drinks, and cereals
  • High-carb fruit, including apples, blueberries, cantaloupe, and strawberries

Foods to restrict on the keto diet (but that you can still eat in small amounts) include:

  • Dairy, which contains a sugar called lactose
  • Fruit
  • Starchy vegetables, including potatoes, butternut squash, beans, lentils, yams, parsnips, and pumpkins

Potential Keto Diet Benefits

While the keto diet isn’t for everyone and is safest to pursue under the guidance of a doctor or dietitian, eating to achieve ketosis has a range of potential benefits. These may include:

  • Weight Loss and Appetite Control Ketosis may help to reduce body fat in people who are overweight or have obesity, especially deep abdominal fat, while preserving muscle mass and reducing hormonal hunger signals and cravings.
  • Better Blood Sugar and Diabetes Management The keto diet can lower blood sugar and insulin levels, improve HbA1c (which measures long-term glucose control), and reduce the need for medications in many people with diabetes.
  • Gut Health Support Being in ketosis may increase the diversity of beneficial gut bacteria and improve the balance of healthy microbes in the digestive system. However, more data is necessary to confirm the potential long-term effects of the keto diet on the gut microbiome.
  • Brain and Cellular Protection Ketone bodies can act as antioxidants that protect brain cells, enhance cellular energy production, and reduce inflammation throughout the body.
  • Adjuvant Support in Cancer Therapy Keto dieting may help to starve cancer cells by cutting off their main glucose supply and making tumors more susceptible to treatments like chemotherapy and radiation. However, limited human data is available in this area, and more research is necessary.

Is Ketosis Safe and Healthy for Everyone?

Some research exposes the potential health risks of the keto diet. For example, some research has linked the keto diet to an increase in LDL (“bad”) cholesterol, due to the high intake of saturated fat.

Following a keto diet also means having to pass on grains, vegetables, and fruits, which can lead to micronutrient deficiencies, especially magnesium, selenium, phosphorus, vitamin C, and some B vitamins. And if you already have liver problems, placing extra load on the organ with an influx of fat to digest can worsen any liver condition you may have.

Plus, the keto diet may overload the kidneys and increase your risk of kidney stones.

It’s also important to note that there have been no long-term studies on the effects of the keto diet, nor has there been research detailing what may happen to the body if it’s in a constant state of ketosis.

People who have conditions involving the thyroid, pancreas, gallbladder, or liver may experience dangerous complications on the keto diet and should avoid it.

Likewise, the following people should also avoid the keto diet:

  • Women who are pregnant or breastfeeding
  • People on certain diabetes medications and insulin
  • People with a low body mass index
  • Children (unless prescribed by a doctor to manage certain types of epilepsy)
  • People with gallstones
  • People who have had their gallbladder removed
  • Anyone with a history of disordered eating

No reliable studies have investigated the long-term effects of constant ketosis. But as a short-term weight loss approach, it appears to be generally safe for most otherwise healthy people.

A review of randomized controlled trials found that keto diets were only slightly more effective for long-term weight loss than more conventional calorie-restriction diets, and it asserted that the evidence assessing the impact of keto diets is generally short term and low quality.

What to Know About Ketosis and Diabetes

Although more research is needed, there is some evidence that following a ketogenic diet and achieving ketosis may be beneficial if you’re living with type 2 diabetes and need to manage your symptoms.

Limiting carbohydrate intake is crucial with type 2 diabetes because too many carbs can increase blood glucose levels.

Consistently raised blood sugar levels can damage blood vessels and lead to vision problems, kidney problems, and nerve problems.

Because you can reach ketosis by restricting your carb intake, this diet may naturally lower your blood glucose levels. And if you’re overweight and living with diabetes, eating fewer carbs may help you lose excess pounds, which is another way to gain control of your blood glucose.

A study comparing the effects of the keto and Mediterranean diets on HbA1c in people with type 2 diabetes and prediabetes found that the keto diet reduced HbA1c by 9 percent from baseline, while the Mediterranean diet reduced it by 7 percent. However, the researchers concluded that the keto diet was lower in several nutrients, especially fiber, compared with the Mediterranean diet. The participants also found the keto diet tougher to maintain in the long term.

Ketosis is an option for many people with type 2 diabetes because they still produce insulin, which helps their body maintain a safe level of ketones in the blood. If you’re considering trying ketosis or the ketogenic diet with type 2 diabetes, be sure to consult your healthcare provider first to ensure it’s safe for you.

This eating approach may interfere with some types of diabetes medication.

What Is the Difference Between Ketosis and Diabetic Ketoacidosis?

Achieving ketosis with type 1 diabetes could cause diabetic ketoacidosis (DKA). This increases the acidity of the blood. Therefore, if you have type 1 diabetes, doctors advise against putting your body in ketosis, to avoid this potentially life-threatening health emergency.

DKA can occur when ketone levels become too high, due to a lack of insulin, which means the cells can’t use glucose for energy. This puts the metabolism into a state of ketosis, and excess ketone production can cause a toxic reaction throughout the body.

DKA can happen to anyone with diabetes, but it is more common in people with type 1 diabetes because their bodies don’t make insulin. It might also occur in people who take insulin to manage diabetes but receive the wrong dose, have a clogged insulin pump, or miss a shot. Being ill and eating less can also make managing blood sugar more difficult.

Without treatment, this condition can lead to a diabetic coma or death.

Symptoms of DKA include extreme thirst and passing urine much more than usual. If you don’t get treatment, these symptoms may progress to the following:

  • Rapid, deep breathing
  • Dry mouth and skin
  • Flushing of the face
  • Fruity-smelling breath
  • Headache
  • Muscle aches or stiffness
  • Extreme fatigue
  • Nausea
  • Vomiting
  • Belly pain
This may sometimes be the first sign of diabetes in people who don’t already have a diagnosis. If you have poorly managed type 1 or type 2 diabetes, test your blood glucose regularly before and after meals, and check your ketone level whenever your blood sugar is above 250 milligrams per deciliter.

Speak to your physician about the best blood glucose level at which to test for ketones.

If your blood ketone level is higher than 1.6 mmol/L, seek immediate emergency medical care.

How Can You Avoid Ketosis?

Some people intentionally achieve ketosis to lose weight by eating a low-carb, high-fat diet. If you don’t want to go into ketosis, eating a balanced diet that includes carbs, fat, and protein can prevent ketosis. Not skipping meals can also help.

Make sure your macronutrient intake has roughly the following balance in terms of the percentage of daily calories that should come from each:

  • Carbs 45 to 65 percent
  • Fat 20 to 35 percent
  • Protein 10 to 35 percent
In other words, if you eat a 2,000-calorie diet, no more than 900 to 1,300 of your calories should come from carbs, which corresponds to about 225 to 325 grams of carbs daily.

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
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Lynn Grieger, RDN, CDCES

Medical Reviewer

Lynn Grieger is a registered dietitian-nutritionist, certified diabetes care and education specialist, certified personal trainer, and certified health and wellness coach. She comp...

Adam Felman

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Adam is a freelance writer and editor based in Sussex, England. He loves creating content that helps people and animals feel better. His credits include Medical News Today, Greatis...