There are several ways to approach the “intermittent” part of food restriction. One of the most common is limiting the window in which food is consumed to about eight hours a day. Another is fasting for a full 24 hours once a week, or once a month. Fasting beyond three days can be stressful on the body and should be done with medical advice and supervision.

Exogenous ketosis comes from an external source. Consuming exogenous ketones, like a ketone drink containing a ketone ester or a ketone salt, raises blood ketone levels. The body isn't producing ketones in this state, but still remains in ketosis from having ketones introduced from an outside source. However, the body isn't ketogenic–that specifically means the body is producing its own ketones.
^ Hochachka PW, Storey KB (February 1975). "Metabolic consequences of diving in animals and man". Science. 187 (4177): 613–21. Bibcode:1975Sci...187..613H. doi:10.1126/science.163485. PMID 163485. In the terminal stages of prolonged diving, however, even these organs must tolerate anoxia for surprisingly long times, and they typically store unusually large amounts of glycogen for this purpose.
The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used primarily to treat difficult-to-control (refractory) epilepsy in children. The diet forces the body to burn fats rather than carbohydrates. Normally, the carbohydrates contained in food are converted into glucose, which is then transported around the body and is particularly important in fueling brain function. However, if little carbohydrate remains in the diet, the liver converts fat into fatty acids and ketone bodies. The ketone bodies pass into the brain and replace glucose as an energy source. An elevated level of ketone bodies in the blood, a state known as ketosis, leads to a reduction in the frequency of epileptic seizures.[1] Around half of children and young people with epilepsy who have tried some form of this diet saw the number of seizures drop by at least half, and the effect persists even after discontinuing the diet.[2] Some evidence indicates that adults with epilepsy may benefit from the diet, and that a less strict regimen, such as a modified Atkins diet, is similarly effective.[1] Potential side effects may include constipation, high cholesterol, growth slowing, acidosis, and kidney stones.[3]
On the ketogenic diet I feel very shaky/anxious from when I wake up til about noon. Eating doesn’t really help. It could be electrolyte related but seems possibly more related to excess cortisol/adrenaline as noon is also when I start to crash and get tired on a more normal diet, and because those 3 am awakenings that worsen simultaneously in ketosis seem to also have to do with HPA axis stuff. Does this side effect potentially also have to do with my fasting blood sugar being elevated?
Net carbs are what we track when following a ketogenic diet. This calculation is pretty straightforward. Net Carbs = Total Carbs – Fiber. For example, one cup of broccoli has 6g of total carbs and 2.4g of fiber. That would mean one cup of broccoli has 3.6g of net carbs. We count Net Carbs  because dietary fiber does not have a significant metabolic effect. 

Don’t fall for it. The keto fad will perish and be replaced by another miracle diet, and another and another, each with a different set of promises that are similar in that they are empty.  Believe me, there exist human beings without killer metabolisms that are still able to eat the foods they enjoy while maintaining a healthy weight. In fact, the reason they are healthy physically is because they’ve chosen not to kid themselves in terms of what is sustainable for them, and instead choose to keep active, toss the Wonder bread, and get in touch their bodies in a way that allows them to eat intuitively. As someone who used to believe this could never, ever be possible for me, I promise that it’s more than possible for you -- it’s essential.
Bulk buy and cook. If you’re someone who doesn’t like to spend a lot of time in the kitchen, this is the best of both worlds. Buying your food at bulk (specifically from wholesalers) can reduce the cost per pound tremendously. Plus, you can make ahead food (bulk cook chicken thighs for pre-made meat, or cook entire meals) that are used as leftovers, so you spend less time cooking.

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Great post!! I’m a 41 year old Master CrossFit athlete, been in keto / LCHF Primal lifestyle for the past 9 years. I feel that my performance has improved a lot and continues to improve pretty significantly. I was a top 200 Master Open Qualifier on 2016 and 2017 and I’m usually on the podium of local competitions so my performance is really not bad…and I’m totally fat adapted. I follow sort of a TKD where I sometimes eat carbs at night during the week, but never above 100g so It doesn’t even kick me out of ketosis due to activity level. I’ve been playing with some measurements and I noticed that my BG reading after high intensity training sessions is really high (up to 180mg/dl). But it goes down fast (sometimes it goes down to 50mg/dl but I show no side effect of hypo, function completely normal). From my research, the high glucose post high intensity is normal and due to the stressful response of the exercise and also because my liver is producing the glucose from gluconeogeneses to provide it for the workouts, when needed. This only happens when the workouts are long, above 30 minutes.
Fascinating stuff and I am quite curious how we know for certain one is actually in ketosis i.e. using ketones as primary fuel source BECAUSE we do know that glucose has a shorter metabolic pathway to burn and under most conditions, given the presence of glucose, that is what the body will default to which is why high fat and high sugar together in diet is so detrimental. So if we use one or more of the above “boosters” and show high levels of blood ketones but also highish levels of glucose (during initial transition) will be mostly burning ketones or still defaulting to glucose?
I was thinking of buying exogenous ketones for my mother. She plays golf daily but gained some weight as of late. My mother does not want to do the diet but I was thinking this might help her with energy and losing weight. Another person told me it would help her. But then I got to thinking, if she went into Ketosis, then wouldn’t she get the keto flu rather than get energy and mental clarity? Would I need to tell her to take it everyday?
The thing is, for keto to work, it can’t just be treated like any other diet, which is really confusing considering all the pundits touting the “keto diet.” Eating a balanced diet in daylight hours and night capping with a “keto bar” from Whole Foods is not going to put you in a state of ketosis, nor is eating keto religiously and bingeing the family sized bag of Doritos twice a week. Putting the word “diet” beside “keto” is a bit misleading because it downplays the outrageous restrictions required to put your body in an unnatural fat-burning state. In order to accomplish the “ketosis” most diet plans talk about, you need to radically change your lifestyle -- and, unlike switching to a balanced diet of whole foods, you must be fairly religious about carb restriction in order to reap the benefits.
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