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 >
Although many hypotheses have been put forward to explain how the ketogenic diet works, it remains a mystery. Disproven hypotheses include systemic acidosis (high levels of acid in the blood), electrolyte changes and hypoglycaemia (low blood glucose).[18] Although many biochemical changes are known to occur in the brain of a patient on the ketogenic diet, it is not known which of these has an anticonvulsant effect. The lack of understanding in this area is similar to the situation with many anticonvulsant drugs.[55]

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.[56] 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.[55]
Another difference between older and newer studies is that the type of patients treated with the ketogenic diet has changed over time. When first developed and used, the ketogenic diet was not a treatment of last resort; in contrast, the children in modern studies have already tried and failed a number of anticonvulsant drugs, so may be assumed to have more difficult-to-treat epilepsy. Early and modern studies also differ because the treatment protocol has changed. In older protocols, the diet was initiated with a prolonged fast, designed to lose 5–10% body weight, and heavily restricted the calorie intake. Concerns over child health and growth led to a relaxation of the diet's restrictions.[18] Fluid restriction was once a feature of the diet, but this led to increased risk of constipation and kidney stones, and is no longer considered beneficial.[3]
Josh Axe, a doctor of natural medicine and clinical nutritionist, estimates that about 25% of people who try a ketogenic diet experience these symptoms, with fatigue being the most common. “That happens because your body runs out of sugar to burn for energy, and it has to start using fat,” he says. “That transition alone is enough to make your body feel tired for a few days.”
Anticonvulsants suppress epileptic seizures, but they neither cure nor prevent the development of seizure susceptibility. The development of epilepsy (epileptogenesis) is a process that is poorly understood. A few anticonvulsants (valproate, levetiracetam and benzodiazepines) have shown antiepileptogenic properties in animal models of epileptogenesis. However, no anticonvulsant has ever achieved this in a clinical trial in humans. The ketogenic diet has been found to have antiepileptogenic properties in rats.[55]
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Bottom line: If you don't measure and calculate exactly each food and ingredient, you won't be able to get into ketosis or maintain it. And who wants to be sitting around measuring and counting everything? Again, this diet really takes the enjoyment out of cooking and eating. (Related: I Had Keto Meals Delivered to See If Sticking to the Diet Was Any Easier)
Achieving ketosis is a pretty straightforward, but it can seem complicated and confusing with all of the information out there.4If you want to learn more about ketosis and the scientific process around it, you can visit a very in-depth discussion about on Dr. Peter Attia’s website. Here’s the bottom line on what you need to do, ordered in levels of importance:
A systematic review in 2016 found and analysed seven randomized controlled trials of ketogenic diet in children and young people with epilepsy.[2] The trials were done among children and young people for whom drugs failed to control their seizures, and only one of the trials compared a group assigned to ketogenic diet with a group not assigned to one.[16] The other trials compared types of diets or ways of introducing them to make them more tolerable.[2] Nearly 40% of the children and young people had half or fewer seizures with the diet compared with the group not assigned to the diet. Only about 10% were still on the diet after a few years.[2] Adverse effects such as hunger and loss of energy in that trial were common, with about 30% experiencing constipation.[16]
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]
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.[57] 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.[55]
Carol- so sorry to hear about your stroke. I am not sure most doctors would approve of this diet due to most not being taught much on nutrition in med school, and most still believe in the old school high carb low fat way of eating. My experience has been a dramatic drop in my blood pressure in only a few weeks after starting this diet (172/105 down to 144/95!). I suggest giving it a trial of a few months to see how it may work for you.
This review is coming both from the perspective of an individual who chooses this WOE and as a dually board certified physician in family practice and medical bariatrics (weight loss medicine). This book provides an invaluable resource in both of these worlds. I deeply appreciate the evidence based information and the straight-forward, easy to understand delivery. It is a wonderful complement to the numerous cookbooks filled with amazing keto recipes Maria and Craig have published. If you are looking for a resource to go to over-and-over again look no further. This is the one!
I can't stress enough how out of the ordinary this is for pre-keto Spyder. He tried going to the Gym a few times, but it was always SO DAMN HARD to get there and he never felt like he belonged. Always felt like the other fit, healthy people in the Gym were silently laughing and judging him for being so overweight. So he stopped going and had a few beers to make him feel better... Which totally helped (make the problem worse). Pre-keto Spyder was a bit depressed and probably a bit of an alcoholic too, but that's a bit cultural in NZ (excuses excuses!)
This lighter soup by I Breathe I’m Hungry offers plenty of fat with coconut milk, chopped pistachios, and coconut flakes. Spices like curry powder and onion flakes make it flavorful. It will even please the non-keto dieters in your family as it’s low in calories, only 117 per serving, and is dairy-free and Whole30 compliant, too. One serving has only 6 grams of net carbs.
While following keto, you’re encouraged to eat as much fat as you want, no matter the source (e.g., butter, olive oil, meats, cheeses), until you feel full. Fat can have a strong satiety effect, but following this recommendation may not be comfortable for everyone. According to recent research, fatty foods may increase feelings of nausea and bloating for some people. Beyond potential physical discomfort, it also might not be emotionally comfortable for everyone—after all, keto is still a restrictive diet, which typically is not a good choice for anyone with a disordered relationship to food and eating. And as with any restrictive dietary plan, following a ketogenic diet can present challenges when it comes to social occasions, celebrations, office parties, meals out, etc. It also might be necessary to limit or avoid culturally relevant foods on the diet in order to stay in ketosis. For still other people it will be tough to sustain because carbs aren’t only delicious, they’re omnipresent. Avoiding them day to day means fastidious meal prep and planning, and planning for social events that include food or eating.

Bottom line: If you don't measure and calculate exactly each food and ingredient, you won't be able to get into ketosis or maintain it. And who wants to be sitting around measuring and counting everything? Again, this diet really takes the enjoyment out of cooking and eating. (Related: I Had Keto Meals Delivered to See If Sticking to the Diet Was Any Easier)


If you're healthy and eating a balanced diet, your body controls how much fat it burns, and you don't normally make or use ketones. But when you cut way back on your calories or carbs, your body will switch to ketosis for energy. It can also happen after exercising for a long time and during pregnancy. For people with uncontrolled diabetes, ketosis is a sign of not using enough insulin.
When a person goes off the ketogenic diet and regains much of their original weight, it’s often not in the same proportions, says Kizer: Instead of regaining lean muscle, you’re likely to regain fat. “Now you’re back to your starting weight, but you no longer have the muscle mass to burn the calories that you did before,” she says. “That can have lasting effects on your resting metabolic rate, and on your weight long-term.”

Christopher D. Gardner, PhD; Alexandre Kiazand, MD; Sofiya Alhassan, PhD; Soowon Kim, PhD; Randall S. Stafford, MD, PhD; Raymond R. Balise, PhD; Helena C. Kraemer, PhD; Abby C. King, PhD, “Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women,” JAMA. 2007;297(9):969-977. http://jama.jamanetwork.com/art icle.aspx?articleid=205916.
Dr. Campos, it is so discouraging to see that you disparage the ketogenic diet based on your assumption that it is very heavy in poor quality processed meats. No diet that relies on processed foods can be viewed as “healthy”. Become better informed by getting up to speed with what Jeff Volek, RD, PhD, calls a “well-formulated ketogenic diet.” Also, learn more about the potential of the diet to slow cancer progression (my specialty). You owe it to your patients who are depending on you for advice. Present them with facts, not opinions.
Advocates for the diet recommend that it be seriously considered after two medications have failed, as the chance of other drugs succeeding is only 10%.[9][30][31] The diet can be considered earlier for some epilepsy and genetic syndromes where it has shown particular usefulness. These include Dravet syndrome, infantile spasms, myoclonic-astatic epilepsy and tuberous sclerosis complex.[9][32]
Our bodies are incredibly adaptive to what you put into it – when you overload it with fats and take away carbohydrates, it will begin to burn ketones as the primary energy source. Optimal ketone levels offer many health, weight loss, physical and mental performance benefits.1There are scientifically-backed studies that show the advantage of a low-carb, ketogenic diet over a low-fat diet. One meta-analysis of low-carbohydrate diets showed a large advantage in weight loss. The New England Journal of Medicine study resulted in almost double the weight loss in a long-term study on ketone inducing diets.
The gist of the eating plan? Taking in so few carbs sends your body into ketosis—a state of burning fat for energy, instead of carbohydrates or sugars, explains Beth Warren, RDN, founder of Beth Warren Nutrition and author of Secrets of a Kosher Girl: A 21-Day Nourishing Plan to Lose Weight and Feel Great (Even If You're Not Jewish). In order to stay in ketosis, you only consume 5% to 10% of your calories from carbohydrates—which for most followers is fewer than 20 grams total per day—and instead eat moderate amounts of protein and high amounts of fat.
With grains, most fruits, and many vegetables off the menu, your digestive tract will bog down. “It’s really hard to get adequate fiber eating that way,” says Notte. “A common side effect is significant constipation.” Not only is constipation unpleasant, but it’s also a sign that your gut isn’t happy. “Everything in the keto diet is low in fiber—and that does not support gut health.”

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.
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