Experts warn that the diet is extremely restrictive and not sustainable, and that it can lead to nutritional deficiencies, high cholesterol, or a serious condition called ketoacidosis. But even before long-term problems set in, many people who try the diet report other unpleasant side effects. These side effects even have a name in the weight-loss world: keto flu.
Although many people find that their energy and stamina improve on a keto lifestyle, trying to do too much in the early stages can worsen keto flu symptoms. Well-known ketogenic researcher Dr. Steve Phinney has conducted studies in endurance athletes as well as obese individuals demonstrating that physical performance decreases during the first week of very-low-carb eating. Fortunately, his research also shows that by week 4, people typically perform better than before they started keto.
The remaining calories in the keto diet come from protein — about 1 gram (g) per kilogram of body weight, so a 140-pound woman would need about 64 g of protein total. As for carbs: “Every body is different, but most people maintain ketosis with between 20 and 50 g of net carbs per day,” says Mattinson. Total carbohydrates minus fiber equals net carbs, she explains.
You probably hear the most about low-carb eating for weight loss, but for some people, the approach could also help optimize their health, says Schmidt. “Research shows that women who are obese or have metabolic problems [may] do better hormonally on lower carbs,” says Schmidt, pointing out that other outcomes of the diet can include better sleep, mental clarity, and increased satiety. (1)
The ketone bodies are possibly anticonvulsant; in animal models, acetoacetate and acetone protect against seizures. The ketogenic diet results in adaptive changes to brain energy metabolism that increase the energy reserves; ketone bodies are a more efficient fuel than glucose, and the number of mitochondria is increased. This may help the neurons to remain stable in the face of increased energy demand during a seizure, and may confer a neuroprotective effect.[56]
Remember, your water and electrolyte intake needs to go up on a keto diet, and dehydration can exacerbate many keto flu symptoms. There’s no hard and fast recommendation for how much water keto dieters should be drinking, Nico says. But in general, you should be sipping enough so that your urine stays clear or pale yellow. As for electrolytes like sodium? A registered dietitian can help you figure out how much more you should be having and the best places to get it. If you're feeling sick and can't see a nutritionist right away, consider mixing a low-carb electrolyte drink into your water.
Switching from a high-carb diet to a very-low-carb diet lowers insulin levels in your body. This is not only healthy but also one of the primary goals of a ketogenic diet. When insulin levels are very low, your liver begins converting fat into ketones, which most of your cells can use in place of glucose. When your body is mainly using ketones and fat for energy, you’re in a state of ketosis.
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.
The ketogenic diet is not considered a holistic or all-natural treatment. As with any serious medical therapy, it may result in complications, although these are generally less severe and less frequent than with anticonvulsant medication or surgery.[28] Common but easily treatable short-term side effects include constipation, low-grade acidosis, and hypoglycaemia if an initial fast is undertaken. Raised levels of lipids in the blood affect up to 60% of children[38] and cholesterol levels may increase by around 30%.[28] This can be treated by changes to the fat content of the diet, such as from saturated fats towards polyunsaturated fats, and if persistent, by lowering the ketogenic ratio.[38] Supplements are necessary to counter the dietary deficiency of many micronutrients.[18]
As low-carb dietitian Franziska Spritzler, RD, CDE, who’s based in Orange County, California, points out, when you cut back on carbs, blood sugar and insulin levels generally go down, which can be a good thing for some people. “Carbs are broken down into glucose, which raises your blood sugar and prompts your pancreas to produce insulin to drive sugar into your cells,” says Spritzler. “When you’re overweight or obese, your blood sugar goes up and your pancreas sends out insulin, but your cells may not be responsive, leading your pancreas to overproduce insulin,” she says. High insulin increases hunger and prompts fat storage, she explains.
Fairly recently, the diet was introduced as a weight-loss diet by an Italian professor of surgery, Dr. Gianfranco Cappello of Sapienza University in Rome. In his 2012 study, about 19,000 dieters received a high-fat liquid diet via a feeding tube inserted down the nose. The study showed an average weight loss of more than 20 pounds in participants, most of whom kept it off for at least a year. The researchers reported a few minor side effects, like fatigue.
Children who discontinue the diet after achieving seizure freedom have about a 20% risk of seizures returning. The length of time until recurrence is highly variable, but averages two years. This risk of recurrence compares with 10% for resective surgery (where part of the brain is removed) and 30–50% for anticonvulsant therapy. Of those who have a recurrence, just over half can regain freedom from seizures either with anticonvulsants or by returning to the ketogenic diet. Recurrence is more likely if, despite seizure freedom, an electroencephalogram shows epileptiform spikes, which indicate epileptic activity in the brain but are below the level that will cause a seizure. Recurrence is also likely if an MRI scan shows focal abnormalities (for example, as in children with tuberous sclerosis). Such children may remain on the diet longer than average, and children with tuberous sclerosis who achieve seizure freedom could remain on the ketogenic diet indefinitely.[46]

The first modern study of fasting as a treatment for epilepsy was in France in 1911.[12] Twenty epilepsy patients of all ages were "detoxified" by consuming a low-calorie vegetarian diet, combined with periods of fasting and purging. Two benefited enormously, but most failed to maintain compliance with the imposed restrictions. The diet improved the patients' mental capabilities, in contrast to their medication, potassium bromide, which dulled the mind.[13]
Those issues can be part of what's known as the “keto flu,” Warren says. Other side effects of the keto diet, all of which are tied to carb withdrawal, can include lightheadedness, nausea, mental fog, cramps, and headaches, in addition to tiredness. Luckily, the keto flu doesn't usually last more than a week—which is coincidentally about when people start to see the number on the scale go down, says Warren.
Because some cancer cells are inefficient in processing ketone bodies for energy, the ketogenic diet has also been suggested as a treatment for cancer.[59][60] A 2018 review looked at the evidence from preclinical and clinical studies of ketogenic diets in cancer therapy. The clinical studies in humans are typically very small, with some providing weak evidence for anti-tumour effect, particularly for glioblastoma, but in other cancers and studies, no anti-tumour effect was seen. Taken together, results from preclinical studies, albeit sometimes contradictory, tend to support an anti-tumor effect rather than a pro-tumor effect of the KD for most solid cancers.[61]

The ketogenic diet is calculated by a dietitian for each child. Age, weight, activity levels, culture, and food preferences all affect the meal plan. First, the energy requirements are set at 80–90% of the recommended daily amounts (RDA) for the child's age (the high-fat diet requires less energy to process than a typical high-carbohydrate diet). Highly active children or those with muscle spasticity require more food energy than this; immobile children require less. The ketogenic ratio of the diet compares the weight of fat to the combined weight of carbohydrate and protein. This is typically 4:1, but children who are younger than 18 months, older than 12 years, or who are obese may be started on a 3:1 ratio. Fat is energy-rich, with 9 kcal/g (38 kJ/g) compared to 4 kcal/g (17 kJ/g) for carbohydrate or protein, so portions on the ketogenic diet are smaller than normal. The quantity of fat in the diet can be calculated from the overall energy requirements and the chosen ketogenic ratio. Next, the protein levels are set to allow for growth and body maintenance, and are around 1 g protein for each kg of body weight. Lastly, the amount of carbohydrate is set according to what allowance is left while maintaining the chosen ratio. Any carbohydrate in medications or supplements must be subtracted from this allowance. The total daily amount of fat, protein, and carbohydrate is then evenly divided across the meals.[37]
The ketogenic diet has been studied in at least 14 rodent animal models of seizures. It is protective in many of these models and has a different protection profile than any known anticonvulsant. Conversely, fenofibrate, not used clinically as an antiepileptic, exhibits experimental anticonvulsant properties in adult rats comparable to the ketogenic diet.[58] This, together with studies showing its efficacy in patients who have failed to achieve seizure control on half a dozen drugs, suggests a unique mechanism of action.[56]
One downside to a ketogenic diet for weight loss is the difficulty maintaining it. “Studies show that weight loss results from being on a low-carb diet for more than 12 months tend to be the same as being on a normal, healthy diet,” says Mattinson. While you may be eating more satiating fats (like peanut butter, regular butter, or avocado), you’re also way more limited in what’s allowed on the diet, which can make everyday situations, like eating dinner with family or going out with friends, far more difficult. Because people often find it tough to sustain, it’s easy to rely on it as a short-term diet rather than a long-term lifestyle.

The statements made on this website or email have not been evaluated by the FDA (U.S. Food & Drug Administration). The products sold on this website are not intended to diagnose, treat, cure, or prevent any disease. The information provided by this website or this company is not a substitute for a face-to-face consultation with your physician, and should not be construed as individual medical advice. Consumer reviews, testimonials and opinions are based on the experiences of individual Kettle & Fire consumers. Kettle & Fire is not suggesting that any individual consumer’s experience with our products is representative of the experience of others. These testimonials are voluntarily provided and are not paid for or offered in exchange for free products..


Early studies reported high success rates; in one study in 1925, 60% of patients became seizure-free, and another 35% of patients had a 50% reduction in seizure frequency. These studies generally examined a cohort of patients recently treated by the physician (a retrospective study) and selected patients who had successfully maintained the dietary restrictions. However, these studies are difficult to compare to modern trials. One reason is that these older trials suffered from selection bias, as they excluded patients who were unable to start or maintain the diet and thereby selected from patients who would generate better results. In an attempt to control for this bias, modern study design prefers a prospective cohort (the patients in the study are chosen before therapy begins) in which the results are presented for all patients regardless of whether they started or completed the treatment (known as intent-to-treat analysis).[19]
If you decide to try the keto diet, be aware that it may be hard to stick to. The very low amount of carbs in the plan is a big change for many people. It also can make you feel tired for a few weeks until your body adapts. To make it a success, it’s a good idea to make a meal plan you can follow, including keto-friendly meals and snacks to keep on hand.

NOTICE: The information contained or presented on this website is for educational purposes only. Information on this site is NOT intended to serve as a substitute for diagnosis, treatment, or advice from a qualified, licensed medical professional. The facts presented are offered as information only - not medical advice - and in no way should anyone infer that we or anyone appearing in any content on this website are practicing medicine. Any diet, health, or nutritional program you undertake should be discussed with your doctor or other licensed medical professional. Seek the advice of a medical professional for proper application of ANY material on this site to your specific situation.
The statements made on this website or email have not been evaluated by the FDA (U.S. Food & Drug Administration). The products sold on this website are not intended to diagnose, treat, cure, or prevent any disease. The information provided by this website or this company is not a substitute for a face-to-face consultation with your physician, and should not be construed as individual medical advice. Consumer reviews, testimonials and opinions are based on the experiences of individual Kettle & Fire consumers. Kettle & Fire is not suggesting that any individual consumer’s experience with our products is representative of the experience of others. These testimonials are voluntarily provided and are not paid for or offered in exchange for free products..

The keto diet emphasizes weight loss through fat-burning. The goal is to quickly lose weight and ultimately feel fuller with fewer cravings, while boosting your mood, mental focus and energy. According to keto proponents, by slashing the carbs you consume and instead filling up on fats, you safely enter a state of ketosis. That’s when the body breaks down both dietary and stored body fat into substances called ketones. Your fat-burning system now relies mainly on fat – instead of sugar – for energy. While similar in some ways to familiar low-carb diets, the keto diet’s extreme carb restrictions – about 20 net carbs a day or less, depending on the version – and the deliberate shift into ketosis are what set this increasingly popular diet apart. In fact, other eating plans are pulling in keto elements, so you can find versions like eco-keto and at least one commercial diet that incorporates keto-friendly products.
×