On the ketogenic diet, carbohydrates are restricted and so cannot provide for all the metabolic needs of the body. Instead, fatty acids are used as the major source of fuel. These are used through fatty-acid oxidation in the cell's mitochondria (the energy-producing parts of the cell). Humans can convert some amino acids into glucose by a process called gluconeogenesis, but cannot do this by using fatty acids.[57] Since amino acids are needed to make proteins, which are essential for growth and repair of body tissues, these cannot be used only to produce glucose. This could pose a problem for the brain, since it is normally fuelled solely by glucose, and most fatty acids do not cross the blood–brain barrier. However, the liver can use long-chain fatty acids to synthesise the three ketone bodies β-hydroxybutyrate, acetoacetate and acetone. These ketone bodies enter the brain and partially substitute for blood glucose as a source of energy.[56]
On a ketogenic diet, you’re generally eating a diet that’s high in fat (roughly 70 percent of your total calories come from fat), moderate in protein (about 20 percent of your calories), and low in carbohydrate (about 5 percent of calories). By limiting carbohydrates (to usually less than 45 grams for the average person), your body lacks the glucose (from carbs) that it normally uses for energy, so it eventually switches over to burning fat as its primary fuel source instead; through a metabolic process called ketosis, the liver converts the fat into fragments of fatty acids called ketones, which power the brain and other organs and tissues.
Increased Energy: Fat and ketone bodies can be utilized as a fuel source for nearly all of the cells in the body. Once the body begins to use ketones as its primary fuel source, there will be a noticeable increase in energy since you are avoiding the ups and downs associated with high-carbohydrate/high-glucose/high-insulin levels that result in feeling lethargic and tired throughout the day.
There are three instances where there’s research to back up a ketogenic diet, including to help control type 2 diabetes, as part of epilepsy treatment, or for weight loss, says Mattinson. “In terms of diabetes, there is some promising research showing that the ketogenic diet may improve glycemic control. It may cause a reduction in A1C — a key test for diabetes that measures a person’s average blood sugar control over two to three months — something that may help you reduce medication use,” she says.
As mentioned, there are a few reasons why the keto diet usually equals weight-loss gold, says Keatley. For starters, people usually reduce their daily caloric intake to about 1,500 calories a day because healthy fats and lean proteins make you feel fuller sooner—and for a longer period of time. And then there’s the fact that it takes more energy to process and burn fat and protein than carbs, so you're burning slightly more calories than you did before. Over time, this can lead to weight loss.
Keto for Diabetes: The ketogenic diet can be an extremely effective therapeutic treatment for diabetes. Since type 2 diabetes is hallmarked by insulin resistance, a ketogenic diet may improve insulin-resistance, associated pathological state via the following: 1) lowering and stabilizing both blood glucose and insulin levels, 2) improving insulin sensitivity, and 3) providing an alternative fuel source through ketone production. Virta Health recently published a report showing patients could rapidly improve glycemic control through reductions in fasting blood glucose, HbA1c, and medication use after 10 weeks of treatment. Patients lost 7% of their body weight on average and reported less hunger. For more information, please visit our friends at Virta Health who are actively working with diabetics (https://www.virtahealth.com).
A study with an intent-to-treat prospective design was published in 1998 by a team from the Johns Hopkins Hospital[20] and followed-up by a report published in 2001.[21] As with most studies of the ketogenic diet, no control group (patients who did not receive the treatment) was used. The study enrolled 150 children. After three months, 83% of them were still on the diet, 26% had experienced a good reduction in seizures, 31% had had an excellent reduction, and 3% were seizure-free.[Note 7] At 12 months, 55% were still on the diet, 23% had a good response, 20% had an excellent response, and 7% were seizure-free. Those who had discontinued the diet by this stage did so because it was ineffective, too restrictive, or due to illness, and most of those who remained were benefiting from it. The percentage of those still on the diet at two, three, and four years was 39%, 20%, and 12%, respectively. During this period, the most common reason for discontinuing the diet was because the children had become seizure-free or significantly better. At four years, 16% of the original 150 children had a good reduction in seizure frequency, 14% had an excellent reduction, and 13% were seizure-free, though these figures include many who were no longer on the diet. Those remaining on the diet after this duration were typically not seizure-free, but had had an excellent response.[21][22]
The Johns Hopkins Hospital protocol for initiating the ketogenic diet has been widely adopted.[43] It involves a consultation with the patient and their caregivers and, later, a short hospital admission.[19] Because of the risk of complications during ketogenic diet initiation, most centres begin the diet under close medical supervision in the hospital.[9]
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Constipation: As mentioned above, the elimination of carbohydrates coupled with the increased release of water may lead to constipation. If this occurs, simply increasing water consumption as well as incorporating more fiber into the diet can alleviate these symptoms. Additionally, some electrolytes like magnesium can also assist with this in higher amounts.
Among the many biological modifications that must occur for sufficient ketone body utilization, the upregulation of ketone transporters must take place. Thus, research has demonstrated that chronic elevations in blood ketone levels positively increase the number of these transporters. Therefore adherence, especially during the initial stages of the keto diet for beginners, is critical.
Although you'll be cutting way back on carbohydrates and sugar, some fruits are still okay to eat on the keto diet (though you'll still want to be mindful about quantity in order to remain in ketosis). The fruits that make the cut contain far fewer carbs than their off-limits cousins such as apples, pears, bananas, pineapples, papayas, grapes, and fruit juices in general.
When in the hospital, glucose levels are checked several times daily and the patient is monitored for signs of symptomatic ketosis (which can be treated with a small quantity of orange juice). Lack of energy and lethargy are common, but disappear within two weeks.[17] The parents attend classes over the first three full days, which cover nutrition, managing the diet, preparing meals, avoiding sugar, and handling illness.[19] The level of parental education and commitment required is higher than with medication.[44]
The ketogenic diet is a mainstream dietary therapy that was developed to reproduce the success and remove the limitations of the non-mainstream use of fasting to treat epilepsy.[Note 2] Although popular in the 1920s and '30s, it was largely abandoned in favour of new anticonvulsant drugs.[1] Most individuals with epilepsy can successfully control their seizures with medication. However, 20–30% fail to achieve such control despite trying a number of different drugs.[9] For this group, and for children in particular, the diet has once again found a role in epilepsy management.[1][10]
Supplemental ketosis: This form of ketosis has recently gained momentum in the field of ketogenic dieting. Supplemental ketosis is a ketogenic state that is achieved through the ingestion of ketogenic supplements. Consuming these substances alone does not mean that an individual is “keto-adapted.” While these products can help during the keto-adaptation period, especially if one is experiencing the “keto-flu,” they will only elicit short-term increases in blood ketone levels. Exogenous ketones can acutely produce benefits similar to the ketogenic diet; however, these products are best used in conjunction with a well-formulated keto diet for beginners, or the very at least, a diet that restricts carbohydrates. The commonly used supplements on the market are medium-chain triglyceride (MCT) oil and exogenous ketones. MCT oil is a fat that, in contrast to other longer-chain fatty acids, travels straight from the intestines to the liver where it is readily metabolized. This allows for ketone production in the liver to occur faster than with other fats (long-chain fatty acids have to travel through the lymph and circulatory systems first). Exogenous ketones are synthetic substances that mimic the ketones produced in our body (endogenous ketones). Exogenous ketones can come in the form of ketone salts or ketone esters.
But there is evidence that low-carb diets may increase metabolism, according to a paper published November 14 in BMJ. Researchers found that overweight adults who lowered carbohydrates and added more fat into their diets burned about 250 calories more each day than people on high-carb, low-fat diets. The study is impressive because it's the largest, most expensive, and controlled study of its kind.
The brain is composed of a network of neurons that transmit signals by propagating nerve impulses. The propagation of this impulse from one neuron to another is typically controlled by neurotransmitters, though there are also electrical pathways between some neurons. Neurotransmitters can inhibit impulse firing (primarily done by γ-aminobutyric acid, or GABA) or they can excite the neuron into firing (primarily done by glutamate). A neuron that releases inhibitory neurotransmitters from its terminals is called an inhibitory neuron, while one that releases excitatory neurotransmitters is an excitatory neuron. When the normal balance between inhibition and excitation is significantly disrupted in all or part of the brain, a seizure can occur. The GABA system is an important target for anticonvulsant drugs, since seizures may be discouraged by increasing GABA synthesis, decreasing its breakdown, or enhancing its effect on neurons.[7]
Still, it can be hard to get enough fat when you first start this diet. Butter, nuts, coconut and olive oils, and fatty cuts of meat are all on the menu. However, don't go overboard with polyunsaturated fats like soybean, corn, or sunflower oil. Keto dieters who increase their intake of those fats often end up with gastrointestinal distress that causes them to jump ship.

Insulin is a hormone that lets your body use or store sugar as fuel. Ketogenic diets make you burn through this fuel quickly, so you don’t need to store it. This means your body needs -- and makes -- less insulin. Those lower levels may help protect you against some kinds of cancer or even slow the growth of cancer cells. More research is needed on this, though.

Carbohydrate-restricted ketosis: This type of ketosis mimics the same biological alterations seen during lengthy fasts, but without the complete restriction of food. Carbohydrate-restricted ketosis is achieved primarily through a very low-carbohydrate ketogenic diet. This restriction, in turn, results in reductions of insulin and blood glucose levels similar to that of fasting, which again increases blood ketone levels. For most individuals, nutritional ketosis is much more sustainable than fasting or starvation ketosis. Fasting can still have its place in a keto diet for beginners. Many individuals following a ketogenic diet like to implement a regular fasting protocol such as intermittent fasting (IF) (12–20 hours daily) or every-other-day fasts (EOD), depending on their goals. This practice is not critical for success on a ketogenic diet, but it can enhance the level of ketone production, and thus magnify the benefits.

On the ketogenic diet, carbohydrates are restricted and so cannot provide for all the metabolic needs of the body. Instead, fatty acids are used as the major source of fuel. These are used through fatty-acid oxidation in the cell's mitochondria (the energy-producing parts of the cell). Humans can convert some amino acids into glucose by a process called gluconeogenesis, but cannot do this by using fatty acids.[57] Since amino acids are needed to make proteins, which are essential for growth and repair of body tissues, these cannot be used only to produce glucose. This could pose a problem for the brain, since it is normally fuelled solely by glucose, and most fatty acids do not cross the blood–brain barrier. However, the liver can use long-chain fatty acids to synthesise the three ketone bodies β-hydroxybutyrate, acetoacetate and acetone. These ketone bodies enter the brain and partially substitute for blood glucose as a source of energy.[56]
Variations on the Johns Hopkins protocol are common. The initiation can be performed using outpatient clinics rather than requiring a stay in hospital. Often, no initial fast is used (fasting increases the risk of acidosis, hypoglycaemia, and weight loss). Rather than increasing meal sizes over the three-day initiation, some institutions maintain meal size, but alter the ketogenic ratio from 2:1 to 4:1.[9]

After about two to seven days of following the keto diet, you go into something called ketosis, or the state your body enters when it doesn't have enough carbs for your cells to use for energy. That's when you start making ketones, or organic compounds that your bod then uses in place of those missing carbs. At this point, your body also starts burning fat for more energy, says Beth Warren, RD, founder of Beth Warren Nutrition and author of Living A Real Life With Real Food.
Also make sure that you know what foods have mostly carbs, fat, and protein, so you can make the right choices. For instance, it’s not just bread, pasta, chips, cookies, candy, and ice cream that contain carbs. Beans may contain protein, but they’re also very high in carbohydrates. Fruit and veggies also mostly contain carbs. The only foods that don’t contain carbs are meat (protein) and pure fats, like butter and oils (including olive oil and coconut oil).
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