^ Greenberg CR, Dilling LA, Thompson GR, Seargeant LE, Haworth JC, Phillips S, Chan A, Vallance HD, Waters PJ, Sinclair G, Lillquist Y, Wanders RJ, Olpin SE (April 2009). "The paradox of the carnitine palmitoyltransferase type Ia P479L variant in Canadian Aboriginal populations". Molecular Genetics and Metabolism. 96 (4): 201–7. doi:10.1016/j.ymgme.2008.12.018. PMID 19217814.

^ Freeman JM, Vining EP, Pillas DJ, Pyzik PL, Casey JC, Kelly LM. The efficacy of the ketogenic diet—1998: a prospective evaluation of intervention in 150 children. Pediatrics. 1998 Dec;102(6):1358–63. doi:10.1542/peds.102.6.1358. PMID 9832569. https://web.archive.org/web/20040629224858/http://www.hopkinsmedicine.org/press/1998/DECEMBER/981207.HTM Lay summary]—JHMI Office of Communications and Public Affairs. Updated 7 December 1998. Cited 6 March 2008.
Physical or mental fatigue during workouts (or while you’re sitting at your office) is caused by the low blood glucose that occurs as your carbohydrate fuel tank approaches empty (also known as the infamous “bonk”, which is awesomely demonstrated in this funniest running cartoon I’ve ever seen). Because it is generally (and sadly) accepted as orthodox knowledge that the human body can’t burn fat as a reliable fuel source – especially when you’re exercising for long periods of time or at high intensities – nearly every shred of nutrition science is simply looking for ways to somehow increase the size of your carbohydrate fuel tank and hack the body to allow it to store more carbs or absorb carbs more quickly.
Carbohydrates help control blood sugar levels, which are of particular importance for people with diabetes. A study published in May 2018 in the journal Diabetic Medicine shows that while a keto diet may help control HbA1c levels (a two- to three-month average of blood sugar levels), the diet may also cause episodes of hypoglycemia, which is a dangerous drop in blood sugar. Echoing many registered dietitians, the Lincoln, Nebraska–based sports dietitian Angie Asche, RD, says she is “hesitant to recommend a ketogenic diet for individuals with type 1 diabetes.”
Hi Cyn, The numbers are general guidelines but will vary depending on many factors, such as activity level, insulin resistance, weight and more. There is no single magic number, just conventional recommendations that are a good starting point. I will have a macro calculator coming soon that will help determine what is best for each person, but even then it’s an approximation. The only way to know for sure is to test. If keto is your goal, it’s usually best to start lower and then see if you can stay in ketosis when increasing.
Nutritional ketosis is a natural metabolic state in which your body adapts to burning fat rather than carbohydrates as its primary fuel. It is clinically proven to directly reduce blood sugar (as measured by HbA1c), improve insulin sensitivity (as measured by HOMA-IR) and reduce inflammation (as measured by white blood cell count and CRP). Nutritional ketosis can be induced by following a ketogenic diet. Learn more in our FAQ below!
I am curious if someone takes any or too much MCT oil (5-10 tablespoons/day) or Exogenous Ketones will the liver slow/stall or shut off endogenous ketone production as you are providing the ketones exogenously and thereby you may NEED to supplement ketones to maintain ketone levels or you may suffer a short term ketone deficit while the liver adjusts to making them on its own again. A parallel I am thinking of is exogenous testosterone supplementation and the hypothalamus/endocrine system slowing/stopping endogenous testosterone production (seen in bodybuilders).
Wilder's colleague, paediatrician Mynie Gustav Peterman, later formulated the classic diet, with a ratio of one gram of protein per kilogram of body weight in children, 10–15 g of carbohydrate per day, and the remainder of calories from fat. Peterman's work in the 1920s established the techniques for induction and maintenance of the diet. Peterman documented positive effects (improved alertness, behaviour, and sleep) and adverse effects (nausea and vomiting due to excess ketosis). The diet proved to be very successful in children: Peterman reported in 1925 that 95% of 37 young patients had improved seizure control on the diet and 60% became seizure-free. By 1930, the diet had also been studied in 100 teenagers and adults. Clifford Joseph Barborka, Sr., also from the Mayo Clinic, reported that 56% of those older patients improved on the diet and 12% became seizure-free. Although the adult results are similar to modern studies of children, they did not compare as well to contemporary studies. Barborka concluded that adults were least likely to benefit from the diet, and the use of the ketogenic diet in adults was not studied again until 1999.[10][14]
The reason purity matters is that C17 is a byproduct of most MCT oil production processes, and it, along with C6, is a major cause of throat burning and gut irritation. Most MCT’s on the market are manufactured via chemical and solvent based refining, which involves using chemicals like hexane and different enzymes and combustion chemicals, such as sodium methoxide. But ideally, you should get an MCT oil that is made using triple steam distillation in a non-oxygen atmosphere to avoid lipid oxidation and create a purer end-product.
You also get incredible gains in metabolic efficiency when you use fat as a primary source of fuel – especially when doing high-intensity interval training – with this one-two combo causing potent 3–5 percent decreases in the oxygen cost of exercise, which is extremely significant. Translated into real- world numbers, this increased fat utilization from carbohydrate restriction and high-intensity interval training would allow you to pedal a bicycle at a threshold of 315 watts, whereas a high-carbohydrate, aerobic-only program (the way most people train) would allow for only 300 watts. Talk to any cyclist and you’ll find out that an 15 extra watts of power is huge in a sport like cycling, and something most cyclists train years and years to achieve.
Here are a few of the most common side effects that I come across when people first start keto. Frequently the issues relate to dehydration or lack of micronutrients (vitamins) in the body. Make sure that you’re drinking enough water (close to a gallon a day) and eating foods with good sources of micronutrients. To read more on micronutrients, click here >
Since the body’s acid-base buffering system cannot neutralize the vast amount of acidic ketones, the blood pH drops significantly. This buildup of acids in the blood poisons the body and can lead to ketoacidosis.12 Breathing becomes deep and rapid as the body attempts to compensate for excessive acids. Other symptoms of diabetic ketoacidosis include:
Nutritional ketosis is a natural metabolic state in which your body adapts to burning fat rather than carbohydrates as its primary fuel. It is clinically proven to directly reduce blood sugar (as measured by HbA1c), improve insulin sensitivity (as measured by HOMA-IR) and reduce inflammation (as measured by white blood cell count and CRP). Nutritional ketosis can be induced by following a ketogenic diet. Learn more in our FAQ below!
"Keto is not a great long-term diet, as it is not a balanced diet," Nancy Rahnama, M.D., M.S., an internal medicine and bariatric specialist, told Reader's Digest. "A diet that is devoid of fruit and vegetables will result in long-term micronutrient deficiencies that can have other consequences. The keto diet can be used for short-term fat loss, as long as it is under medical supervision."

This is an absolutely necessary function for basic survival. As the body can only store carbs for a day or two, the brain would quickly shut down after a couple of days without food. Alternatively it would quickly have to convert our muscle protein into glucose – a very inefficient process – just to keep the brain going. That would make us waste away quickly. It would also ensure that the human race could hardly have survived all those millennia before we had 24-7 food availability.


Elevated blood ketone levels is the sign of ketosis, while certain subjective symptoms can also signal ketosis. Increased mental clarity, less brain fog, and diminished appetite are fairly common among people in ketosis. The ketogenic diet specifically has its own assortment of symptoms. Fortunately, the negative symptoms such as constipation, diarrhea, and bad breath are often temporary and tend fade as your body becomes better at fat burning and naturally producing ketones. The positive symptoms of ketosis coincide with higher levels of ketones in the blood. This may occur after several weeks of adhering to the ketogenic diet or very shortly after ingesting exogenous ketones.
You state that many athletes and very active people could benefit from 100-200g of carbs a day, and be back in ketosis in a few hours. Any particulars on which kind of activities or say how long/many training sessions would benefit from this to balance hormones. I train mma 3-4 days a week and also do lots of hiit and strength training as well. Just trying to see if this is a situation where i would benefit from your suggestions. Thanks!
But beyond that, experts aren't convinced that the keto diet has any other scientifically-proven health benefits. In fact, it may have some distinct downsides. If you follow the keto diet incorrectly, for example (like by eating lots of saturated fats, versus healthy unsaturated fats), you're at risk of raising your cholesterol levels. “The best strategy to keep your heart healthy is to get as much fat as possible from unsaturated sources such as olive, avocado and canola oils, nuts, seeds, avocados, and olives," says Ansel.
Great article! As someone who just started a “ketogenic diet” two weeks ago, I am opting to hold off on using ketone supplements for the following reason. You state how “Keto-adaptation occurs when you have shifted your metabolism to relying on fat-based sources, instead of glucose (sugar) sources, as your primary source of fuel.” If the goal is to “switch” our body’s energy supply to ketones and one uses supplemental ketones, how do they really ever know if their body has successfully accomplished this goal if they are using supplemental ketones? Aren’t they getting a false sense of ketosis if their blood or breath tests show them above 0.5 millimolar through the use of the supplements? I understand that it may take me longer to reach ketosis naturally but I guess I see it was worth it to truly reap all of the benefits that you outline in your article.
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Keep up electrolytes. The major electrolytes in our bodies are sodium, potassium and magnesium. Because a low carb diet (especially a keto diet!) reduces the amount of water you store, this can flush out electrolytes and make you feel sick (called “keto flu”). This is temporary, but you can avoid or eliminate it by salting your food liberally, drinking broth (especially bone broth), and eating pickled vegetables. Some people also choose to take supplements for electrolytes, but it’s best to first consult a doctor that understands and supports keto/low carb lifestyles.
About 20% of children on the ketogenic diet achieve freedom from seizures, and many are able to reduce the use of anticonvulsant drugs or eliminate them altogether.[18] Commonly, at around two years on the diet, or after six months of being seizure-free, the diet may be gradually discontinued over two or three months. This is done by lowering the ketogenic ratio until urinary ketosis is no longer detected, and then lifting all calorie restrictions.[46] This timing and method of discontinuation mimics that of anticonvulsant drug therapy in children, where the child has become seizure-free. When the diet is required to treat certain metabolic diseases, the duration will be longer. The total diet duration is up to the treating ketogenic diet team and parents; durations up to 12 years have been studied and found beneficial.[9]
In the 1960s, medium-chain triglycerides (MCTs) were found to produce more ketone bodies per unit of energy than normal dietary fats (which are mostly long-chain triglycerides).[15] MCTs are more efficiently absorbed and are rapidly transported to the liver via the hepatic portal system rather than the lymphatic system.[16] The severe carbohydrate restrictions of the classic ketogenic diet made it difficult for parents to produce palatable meals that their children would tolerate. In 1971, Peter Huttenlocher devised a ketogenic diet where about 60% of the calories came from the MCT oil, and this allowed more protein and up to three times as much carbohydrate as the classic ketogenic diet. The oil was mixed with at least twice its volume of skimmed milk, chilled, and sipped during the meal or incorporated into food. He tested it on 12 children and adolescents with intractable seizures. Most children improved in both seizure control and alertness, results that were similar to the classic ketogenic diet. Gastrointestinal upset was a problem, which led one patient to abandon the diet, but meals were easier to prepare and better accepted by the children.[15] The MCT diet replaced the classic ketogenic diet in many hospitals, though some devised diets that were a combination of the two.[10]
The low glycaemic index treatment (LGIT)[49] is an attempt to achieve the stable blood glucose levels seen in children on the classic ketogenic diet while using a much less restrictive regimen. The hypothesis is that stable blood glucose may be one of the mechanisms of action involved in the ketogenic diet,[9] which occurs because the absorption of the limited carbohydrates is slowed by the high fat content.[5] Although it is also a high-fat diet (with approximately 60% calories from fat),[5] the LGIT allows more carbohydrate than either the classic ketogenic diet or the modified Atkins diet, approximately 40–60 g per day.[18] However, the types of carbohydrates consumed are restricted to those that have a glycaemic index lower than 50. Like the modified Atkins diet, the LGIT is initiated and maintained at outpatient clinics and does not require precise weighing of food or intensive dietitian support. Both are offered at most centres that run ketogenic diet programmes, and in some centres they are often the primary dietary therapy for adolescents.[9]
After initiation, the child regularly visits the hospital outpatient clinic where they are seen by the dietitian and neurologist, and various tests and examinations are performed. These are held every three months for the first year and then every six months thereafter. Infants under one year old are seen more frequently, with the initial visit held after just two to four weeks.[9] A period of minor adjustments is necessary to ensure consistent ketosis is maintained and to better adapt the meal plans to the patient. This fine-tuning is typically done over the telephone with the hospital dietitian[19] and includes changing the number of calories, altering the ketogenic ratio, or adding some MCT or coconut oils to a classic diet.[18] Urinary ketone levels are checked daily to detect whether ketosis has been achieved and to confirm that the patient is following the diet, though the level of ketones does not correlate with an anticonvulsant effect.[19] This is performed using ketone test strips containing nitroprusside, which change colour from buff-pink to maroon in the presence of acetoacetate (one of the three ketone bodies).[45]
And here’s the reality of the situation. Not all carbs are created equal. There’s a lot of cleverly labeled and modified maltodextrin on the market claiming to be some technical polysaccharide. Or, there’s plain old cornstarch relabeled as super-duper muscle engorging waxy maize. Most of these aren’t proven to do anything except deliver false hopes, high blood sugar, and gut issues – as opposed to having multiple clinical studies in real athletes to support what it is they’re claiming.
Why is the keto diet good for you? A keto diet is one that prioritizes fats and proteins over carbohydrates. It can help reduce body weight, acne, and the risk of cancer. Find out about the mechanisms through which it achieves these benefits and the research that supports it. This MNT Knowledge Center article also discusses the risks of the diet. Read now
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