Ketosis is a metabolic state that can help you shed fat fast — here's how to reach it
- Ketosis is a metabolic state in the body where fat is used for energy instead of carbohydrates.
- The body can reach ketosis in about two days to a week through a low carb, high-fat diet, like the ketogenic diet.
- Low-carb diets have been shown to help people shed pounds and fat faster than other diets, but they don't necessarily help you shed more weight long-term.
- This article was medically reviewed by Samantha Cassetty, MS, RD, nutrition and wellness expert with a private practice based in New York City.
The ketogenic diet, or keto for short, may seem like just another fad, but scroll through social media and you'll see many showing off their weight loss success. The keto diet works by literally changing the way your body uses energy.
Normally, the body converts carbohydrates, or sugar, into glycogen for energy. But on the ketogenic diet, carbs are drastically reduced so that the body can enter a metabolic state called ketosis — where you burn fat for energy instead of glycogen.
However, it's not always easy to enter ketosis. And your body won't immediately reach this fat-burning state after a day of cutting carbohydrates. It takes time, and it may be difficult to know when you've reached that point. Here are some tips to help you know when you've reached ketosis and how to get there a little faster.
Reaching ketosis faster
To reach ketosis, you must first reduce your body's glycogen reserves. The keto diet helps you do that by limiting carbohydrates to less than 50 grams per day. That's about the equivalent amount of carbs in two large apples.
After about two days to a week of restricting carbs, your body should start tapping into fat reserves for energy. But this can vary person to person and may take slightly longer. Some ways you can speed up the process is:
- Fast. Studies involving children with epilepsy show fasting for two or three days triggers ketosis quickly.
- Exercise. Physical activity is powered by carbohydrates and will help you deplete your glycogen reserves more quickly.
- Avoid supplements. Supplements like keto pills claim they can kick start ketosis faster, but preliminary studies suggest otherwise.
Signs you've reached ketosis
Common symptoms of the keto diet include:
- Headache
- Fatigue
- Dizziness
- Nausea
- Brain fog
- Gastrointestinal discomfort
- Low energy
- Feeling faint
These symptoms are often called the keto flu, and are a side effect of your body's transition to a constant state of ketosis. After four to six weeks your body will adapt and these side effects should resolve.
Other ways to check that you're in ketosis is with urine test strips or at-home blood and breath tests. These tests measure the ketone levels in your system. Ketones are the byproduct of fatty acids the body breaks down when you're in ketosis.
A blood test is the most accurate way to measure ketones and is used in doctor's offices, but involves a needle prick. However, urine strips and breath meters are also accurate and less invasive. According to one small 2016 study, urine strips offer the most accurate readings early in the morning and right after dinner.
Benefits of ketosis
The keto diet was developed in the 1920s as an effective treatment for children with epilepsy who were not responding to drugs that were available at the time.
Today it's also used as a medical diet to treat other diseases, like type 2 diabetes and obesity. Studies show that ketones provide energy without elevating blood sugar levels, which reduces the need for insulin. In one clinical trial, people with type 2 diabetes were able to decrease their medication dosage after 12 months of a ketogenic diet.
There are also hints this diet may be good for brain health. In 2019, a small study showed a low-carb diet may improve memory in adults who have mild cognitive problems, potentially an early sign of Alzheimer's disease. One possible explanation is that brains of people with Alzheimer's disease don't use glucose as efficiently, and ketones may be an easier source of energy for overall brain function.
But beyond low blood sugar levels and possible brain health, the keto diet's recent claim to fame is for weight and fat loss. Low carbohydrate diets, in general, have been shown to lead to more rapid weight loss compared to other diets, but not necessarily more weight loss long-term.
For example, in one trial, lasting six months, obese women following a low-carb diet lost nearly 10 pounds more than participants following a low-fat diet. They also lost significantly more body fat — 10.5 pounds versus 4.4 pounds.
Researchers note, though, that most weight loss studies have been short term, so it is unclear how this diet performs for long-term weight loss.
Downsides of ketosis
Despite the weight loss and other potential health benefits, Lorraine Turcotte, a metabolism researcher at the University of Southern California says she would not recommend this extreme diet over a more moderate approach to eating.
"There is a potential benefit [for weight loss] but I would never recommend it unless you are clinically managed," she says.
One reason she would not recommend the diet, especially to athletes, is because it can lead to a breakdown of muscles—the body cannot operate optimally without carbohydrates, so it may resort to using muscle stores instead.
"The body breaks down muscle protein into amino acids and then uses the amino acids to make glucose," says Turcotte. It is not clear if consuming so much fat, especially if the diet is heavy in saturated fat, is good for cardiovascular health long term either — cardiologists say the diet could lead to high cholesterol. In addition, over time, ketosis can cause side effects like kidney stones and constipation in children following the diet for epilepsy treatment.
Turcotte also says that leaving out carbohydrate-rich food groups like fruits, whole grains, and legumes can also lead to a nutritionally-deficient diet lacking many vitamins, minerals and phytochemicals, which are essential to overall health. Besides that, she says, it is just a very strict regime to stay on for a long period of time even for the most "die-hard keto dieters."