That’s why the Bulletproof Diet uses cyclical nutritional ketosis, and why on days when I eat carbohydrates, I always have Brain Octane Oil so my cells have a steady supply of ketones. This builds metabolic flexibility: you can eat fat and carbs and your body will use them both, which is the goal. You want to be resilient and full of energy no matter what, and that means you want cells strong enough to burn whatever you give them.
“Suddenly and drastically reducing carbohydrates sets your body up for a double whammy of sorts,” says Yawitz. “The brain’s favorite fuel is glucose, which is most easily created from carbohydrates. In very-low-carb diets, the brain has to adjust to using ketones from digested fats for energy. To add to this discomfort, your kidneys release more electrolytes as insulin levels fall.” Additionally, your total body water decreases as carbohydrates become depleted on a keto diet, notes Clark. The result? What’s known as the keto flu, which could cause constipation, nausea, headache, fatigue, irritability, cramps, and other symptoms. Don’t fret, though: Many of these symptoms are short term and should last only a few days to weeks. Make sure to drink plenty of water to help your body cope with these symptoms. And call your doctor if symptoms — especially nausea — are prolonged, advises Yawitz.
Essentially, the keto diet for beginners works by “tricking” the body into acting as if its fasting (while reaping intermittent fasting benefits), through a strict elimination of glucose that is found in carbohydrate foods. Today the standard keto diet goes by several different names, including the “low-carbohydrate” or “very-low-carbohydrate ketogenic diet”(LCKD or VLCKD for short).
Technically speaking, you're in ketosis when your blood ketones are higher than 0.5 mmol/L, but the optimal level for fat-burning purposes is 1.5 to 3 mmol/L. Nisevich Bede says that seasoned keto dieters report that they can actually feel a difference in this state, citing that they're less hungry and experience mental clarity once they reach ketosis.
At the first visit, participants were instructed how to follow the LCKD as individuals or in small groups, with an initial goal of ≤20 g carbohydrate per day. Participants were taught the specific types and amounts of foods they could eat, as well as foods to avoid. Initially, participants were allowed unlimited amounts of meats, poultry, fish, shellfish, and eggs; 2 cups of salad vegetables per day; 1 cup of low-carbohydrate vegetables per day; 4 ounces of hard cheese; and limited amounts of cream, avocado, olives, and lemon juice. Fats and oils were not restricted except that intake of trans fats was to be minimized. Participants were provided a 3-page handout and a handbook [11] detailing these recommendations. Participants prepared or bought all of their own meals and snacks following these guidelines.
Based on what we know from the available research, is the keto diet safe? The evidence is clear that the KD can reliably help to treat obesity and improve insulin resistance, but the long-term impact of the KD on cardiovascular risk factors, liver disease and glucose tolerance is more controversial. Experts agree that genetics seem to play a role in how different people respond to the KD, meaning some may be more likely to thrive on very low-carb diets, while others are more susceptible to developing side effects.
In a March 2018 blog post, Dr. Ede provides a range of very helpful tips for anyone already on mood-altering or psychiatric medications who want to try a ketogenic diet, such as how to talk with your psychiatrist or mental-health provider and what laboratory metabolic tests the doctor should order to help monitor your response to the diet. Most importantly, she provides details about some specific medications — notably specific antipsychotic medications, anticonvulsant medications, and lithium — that should be carefully monitored.
The relation between a high fat diet and cancer is not conclusive. Recent epidemiological studies (17,58–60) could not explain a specific causal relationship between dietary fat and cancer. It has been found that altered energy metabolism and substrate requirements of tumour cells provide a target for selective antineoplastic therapy. The supply of substrates for tumour energy metabolism can be reduced by dietary manipulation (eg, ketogenic diet) or by pharmacological means at the cellular level (eg, inhibitors of glycolysis or oxidative phosphorylation). Both of these techniques are nontoxic methods for controlling tumour growth in vivo (61). Sugar consumption is positively associated with cancer in humans and test animals (58–61). This observation is quite logical because tumours are known to be enormous sugar absorbers. It has also been found that the risk of breast cancer decreases with increases in total fat intake (16). Further studies on the role of a ketogenic diet in antineoplastic therapy are in progress in our laboratory.
Often caused by lymph node removal or damage due to cancer treatment, lymphedema occurs because there’s a blockage in the lymphatic system and results in the swelling in leg or arm. A 2017 study involved patients who suffered from obesity and lymphedema and who embarked on a 18-week ketogenic diet. Weight and limb volume was significantly reduced. (5)
The following measurements were made every other week: anthropometric and vital sign measurements; urine testing for ketones; and assessment for hypoglycemic episodes and other symptomatic side effects. Weight was measured on a standardized digital scale while the participant was wearing light clothes and shoes were removed. Skinfold thickness was measured at 4 sites – the average of 2 measurements at each site was entered into an equation to calculate percent body fat [12]. Waist circumference was measured at the midpoint between the inferior rib and the iliac crest using an inelastic tape; 2 measurements were averaged in the analysis. Blood pressure and heart rate were measured after the participant had been seated quietly without talking for 3 minutes. Certified laboratory technicians assessed urine ketones from a fresh specimen using the following semi-quantitative scale: none, trace (up to 0.9 mmol/L [5 mg/dL]), small (0.9–6.9 mmol/L [5–40 mg/dL]), moderate (6.9–13.8 mmol/L [40–80 mg/dL]), large80 (13.8–27.5 mmol/L [80–160 mg/dL]), large160 (>27.5 mmol/L [160 mg/dL]). Hypoglycemic episodes and symptomatic side effects were assessed by direct questioning of the participant and by self-administered questionnaires.
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Incidentally , there’s a very informative article on the bbc website about one of the last remaining hunter/gather societies left in the world, living in Tanzania. They have amazing gut health and no t2d. Would you like to guess at the type of diet they follow? This would be the caveman diet that the writer mentions, and yes these people might not live as long as us but the cause of death is never a lack of motivation to stay on a keto diet.
Some athletes swear by the ketogenic diet, not just for weight loss but for improved performance in their sport, as well. But Edward Weiss, PhD, associate professor of nutrition and dietetics at Saint Louis University, doesn’t buy it. “I hear cyclists say all the time that they’re faster and better now that they’re on keto, and my first question is, 'Well, how much weight did you lose?'” he says.
I can’t tell you how often through the years I have been asked the question, “If I lose 20 pounds, will I no longer have diabetes?” Let me answer this very clearly, there is currently no cure for diabetes. Once you have been diagnosed, you have it for life. Every day, our most brilliant researchers are busy searching for a cure though. There is good news however; you can manage your diabetes, get it under control, prevent all the complications of diabetes and live a normal, healthy life.
The ketogenic diet is a high-fat, low-carbohydrate, and moderate-protein diet that has been proved to be an effective treatment among patients with epileptic conditions such as glucose transporter 1 deficiency, pyruvate dehydrogenase deficiency, tuberous sclerosis complex, Rett syndrome, Dravet syndrome, and specific mitochondrial disorders (1, 2).
The only difficulty with some of these studies is that they tend to have small sample sizes, like this one that only has five cyclist participants and the data was largely skewed by the fact that only ONE cyclist experienced a large enhancement of exercise capacity after the keto diet. Their studies also tend to be short term. Back in 2014, Phinney and scientist Tim Noakes wrote an editorial that stated that in the past 31 years, there have only been a handful of studies measuring sports performance and low carb diets. Out of a total of 11, only 3 found exercise improvements.

Our bodies run well on glucose (carbs)–they give us the necessary energy we need to function on a daily basis. When our body doesn’t get enough glucose (either because we’re cutting carbs too low, OR we haven’t eaten in too long), our body kind of freaks out and looks for other forms of energy to satisfy that role. That’s where the fat comes in. Without carbs, our insulin levels drop and fat is released from our cells. The fat overwhelms the liver which turns it into ketones, our body’s second choice to carbs for energy.
Now, there’s even evidence that a low-carb, high-fat regimen (as the keto diet is) helps you live longer, compared to a low-fat diet. In a study by the medical journal The Lancet that studied more than 135,000 adults from 18 countries, high carbohydrate intake was associated with higher risk of total mortality, whereas total fat and individual types of fat were related to lower total mortality. Total fat and types of fat were not associated with cardiovascular disease, myocardial infarction or cardiovascular disease mortality.
Once ketosis is established, most people experience more stable and lower blood sugar levels. Low-carb diets can be an effective way for people with type 2 diabetes to get a handle on glycemic control—and carb monitoring has long been thought to be an effective way to control blood sugar—though one study concluded low-carb diets are not necessarily a better long-term strategy than other diets. Anecdotal evidence abounds from people with type 2 diabetes who have used the keto diet to stabilize their blood sugar and were able to quit taking their diabetes medication. But it’s not recommended that people with diabetes begin the keto diet without first talking to their doctor.
What are the side effects of the ketogenic diet?  It’s not uncommon for people beginning the keto diet to experience “keto flu” symptoms, which can include: irritability, cravings, menstruation issues in women, constipation, fatigue, headaches and poor exercise performance. These side effects are due to the body going through major metabolic shifts and essentially withdrawing from carbs and sugar.
She has found that when women stick to eating a lighter dinner, and then abstain from eating for about 13–15 hours between dinner and breakfast, they experience improvements in their weight, blood sugar control, etc. She recommends that women try avoiding eating after 8 p.m. or experiment with eating only two meals per day, with tea or broth between meals to help curb hunger. Another option is to try skipping dinner altogether on 1–2 days per week. For most women, when attempting IMF, it’s not recommended to snack between meals unless the woman is very active (such as an athlete in training) or dealing with a hormonal issue such as adrenal burnout.
Financial disclosures: There were no conflicts of interest reported except for Dr Bernstein who has received royalties for books on the management of diabetes (which were used by members of the online social media group surveyed in this study). Dr. Hallberg who holds stock options and receives research support from Virta Health, and consulting fees from Atkins. Dr. Rhodes is the site principal investigator in clinical trials for pediatric type 2 diabetes that are sponsored by Merck and AstraZeneca. Dr. Westman has an ownership interest in companies using low-carbohydrate principles, and he receives royalties for books related to low-carbohydrate diets. Dr. Ludwig has received royalties from books on nutrition and obesity; and Dr. Galati is author of Eating Yourself Sick: How to stop obesity, fatty liver, and diabetes from killing you and your family (2018).
I must tell you when looking at this link they say the American Diabetes Association Guidelines call for 60-75 carbohydrates per meal and that is simply not true. The ADA has recommended since 2013 we use our best clinical judgement in recommending a low carbohydrate diet for people with diabetes, recognizing it needs to be individualized. 60-75 grams is the carbohydrate amount I would give to a very tall, large boned man or perhaps an active teen or young adult. I would never recommend that many carbohydrates for an average size man who was trying to lose weight; he would get 45-60 grams of carbohydrates per meal and 15-30 grams for snacks. A women trying to lose weight would get 30-45 grams of carbohydrates per meal and 15 grams for snacks.
"Many of the richest sources of fiber, like beans, fruit, and whole grains are restricted on the ketogenic diet," registered dietician Edwina Clark told Everyday Health. "As a result, ketogenic eaters miss out on the benefits of fiber-rich diet such as regular laxation and microbiome support. The microbiome has been implicated in everything from immune function to mental health."

This means that instead of generating tons of ketones from the very beginning, most people experience hypoglycemia for a period of time. With hypoglycemia comes a disruption in cortisol signaling which is what accounts for the HPA axis dysfunction. Finally, HPA axis dysfunction leads to an increase in secretion of minerals from the body in the urine.
"The diet was introduced in the 1920s as a way to treat epilepsy and then sort of fell out of popularity with the introduction of anti-seizure drugs," Turoff says. What's more, ketosis (the goal of keto, a state where the body uses fat for energy instead of carbs) is something seen in people during periods of starvation—including in people with anorexia nervosa. "The body is deprived of carbohydrates and thus has to turn to ketone bodies as a fuel source," Turoff explains. "People really need to understand that it's not just a low-carbohydrate, high-fat diet—it actually changes the way your body uses fuel."
That’s why the Bulletproof Diet uses cyclical nutritional ketosis, and why on days when I eat carbohydrates, I always have Brain Octane Oil so my cells have a steady supply of ketones. This builds metabolic flexibility: you can eat fat and carbs and your body will use them both, which is the goal. You want to be resilient and full of energy no matter what, and that means you want cells strong enough to burn whatever you give them.
Finally, wait it out. Certain folks who do everything by the book and follow every bit of good advice may still get a few symptoms of the keto flu. This usually comes in the initial three weeks of entering nutritional ketosis, and things get much better very quickly. Trust that your lull will pass and your energy will increase substantially—usually within a few days.
As far as the the Ketogenic Diet goes, it is a very personal decision between you and hopefully your physician. I would just recommend working closely with your physician for all the recommended lab tests to make sure you remain healthy while on the diet. That’s really the goal of any “diet” anyway, right? To get healthy? This is why we normally always recommend moderation with everything…moderation in the foods you eat along with moderate amounts of exercise equals a healthy lifestyle that will prevent diabetes or help you control your diabetes if you already have it.
Insulin resistance is caused by several mechanisms, one of which is chronically elevated insulin levels. So what increases insulin levels? Mainly sugar. A poor nights sleep can do it too, but sugar is a big one. This can be sugar that is part of our diet or carbohydrates that are broken down to glucose or other simple carbs. Proteins put together with fats can also be converted into sugar, a process called gluconeogenesis. However, it is really the effect of dietary refined sugars and starches (flour) causing blood sugar and insulin spikes (not protein). These insulin spikes from added sugars and flour are then often followed by a blood sugar crash, leading to a sense of discomfort, even sweating, and usually a craving for more high-carb foods.
These findings were confirmed in another interesting study. Researchers compared the effects of the low-carbohydrate diet to the effects of a combination of a low-fat diet and orlistat (a weight-loss and blood pressure lowering medication) on blood pressure. The researchers stated that the low-carbohydrate dietary intervention “was more effective for lowering blood pressure.”
Casual chronic keto is at some risk of those same side effects. Sure, there are sporadic anecdotal cases where there appears (so far) to be no harm, but these are not large population RCTs. The KD-in-epilepsy data is closer to being RCT data. There being no ancestral case for chronic keto, we need to learn what we can from the formal studies (and sure, endeavor to separate the ailment, med and diet effects).
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

Your kidneys flushing out all that water is also part of the reason people see dramatic scale drops in the beginning of their keto journeys. "I wish people knew that the weight loss they will initially experience on this diet is largely due to water loss," Brown says. That means you're most likely not actually losing fat in the first couple of weeks, but instead losing water that will come back in the form of glycogen stores if and when you start eating carbs again. (BTW, Here's How to Safely and Effectively Come Off the Keto Diet.)
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.
AND i’m losing weight! I’m losing about 1 lb per week and actually have the energy again to workout regularly. If you have diabetes, you know how fatiguing of a disease it can be. I feel less sluggish, more “awake”, just better in general, while restricting my carb intake. Yeah, I miss some fruits, but I sure as heck don’t miss what I felt like after eating them. Besides, berries are allowed on keto 🙂
Financial disclosures: There were no conflicts of interest reported except for Dr Bernstein who has received royalties for books on the management of diabetes (which were used by members of the online social media group surveyed in this study). Dr. Hallberg who holds stock options and receives research support from Virta Health, and consulting fees from Atkins. Dr. Rhodes is the site principal investigator in clinical trials for pediatric type 2 diabetes that are sponsored by Merck and AstraZeneca. Dr. Westman has an ownership interest in companies using low-carbohydrate principles, and he receives royalties for books related to low-carbohydrate diets. Dr. Ludwig has received royalties from books on nutrition and obesity; and Dr. Galati is author of Eating Yourself Sick: How to stop obesity, fatty liver, and diabetes from killing you and your family (2018).
Polycystic Ovary Syndrome (PCOS) Because women with the infertility condition PCOS are at a greater risk for diabetes and obesity, some clinicians recommend the keto diet, says Taylor Moree, RD, LD, of Balance Fitness and Nutrition in Atlanta. But PCOS is no different from most health conditions mentioned here: Long-term research on the safety is needed.
In the present study, 83 obese patients (39 men and 44 women) with a body mass index greater than 35 kg/m2, and high glucose and cholesterol levels were selected. The body weight, body mass index, total cholesterol, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, triglycerides, fasting blood sugar, urea and creatinine levels were determined before and after the administration of the ketogenic diet. Changes in these parameters were monitored after eight, 16 and 24 weeks of treatment.

Constipation is a common side effect of low-carb eating plans, including the ketogenic diet. Severely curbing your carb intake means saying goodbye to high-fiber foods like whole grains, beans, and a large proportion of fruits and vegetables, says Ginger Hultin, MS, RDN, Seattle-based nutritionist and spokesperson for the Academy of Nutrition and Dietetics.
However, the lower calorie Keto Diet also features a reduction in fats as well. In doing so, this Keto Diet accelerates fat loss and is better suited for losing weight. After all, between 2 Ketogenic Diet types, with one having a higher caloric intake than the second, which do you think would be the better choice for weight loss? Obviously the lower calorie diet. By reducing fats, your caloric intake is also reduced. As a result, the dieter’s weight loss will occur more rapidly.
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.”
In a survey of both children and adults, researchers found that a very low carbohydrate diet promotes “exceptional glycemic control” in those with type 1 diabetes mellitus. When it comes to type 2 diabetes, the Journal of American Medical Association recently published a review examining the effective use of the ketogenic diet in those with type 2 diabetes.
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