In other words, I personally found that while following “strict ketosis”, things became eerily similar to the days in college when I was a competitive bodybuilder pursuing sub-3% body fat percentages. I simply wasn’t the most fun guy to hang out with in social situations due to my extreme dietary restrictions, the intense self-control became nearly exhausting, and when I traveled, I missed out on many culinary experiences, such as homemade ravioli in Rome, freshly baked crostinis in the Basque regions of Spain, and Korean rice bowls in Seoul.
Once inside the mitochondrion, the dominant way that the bound fatty acids are used as fuel in cells is through β-oxidation, which cleaves two carbons off of the acyl-CoA molecule in every cycle to form acetyl-CoA. Acetyl-CoA enters the citric acid cycle, where it undergoes an aldol condensation with oxaloacetate to form citric acid; citric acid then enters the tricarboxylic acid cycle (TCA), which harvests a very high energy yield per carbon in the original fatty acid.
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.
^ Lawrie 2014, pp. 92-. "A much delayed onset of rigor mortis has been observed in the muscle of the whale (Marsh, 1952b). The ATP level and the pH may remain at their high in vivo values for as much as 24h at 37ºC. No adequate explanation of this phenomenon has yet been given; but the low basal metabolic rate of whale muscle (Benedict, 1958), in combination with the high content of oxymyoglobin in vivo (cf 4.3.1), may permit aerobic metabolism to continue slowly for some time after the death of the animal, whereby ATP levels can be maintained sufficiently to delay the union of actin and myosin in rigor mortis."
Intermittent fasting is another way to achieve ketosis. This doesn’t suggest going days without food, but rather intermittent fasting. You can eat for eight hours and then fast for 16 hours, or eat a low-calorie diet for a few days (about 1,200 daily calories if you’re a woman and 1,500 daily calories if you’re a man). As you take in less food, your body uses more of its fat stores for fuel.
For example, in trained people and athletes who eat a low-carbohydrate, high-fat diet (not to be confused with a low-carbohydrate, high-protein diet), a large amount of fat burning can take place at intensities well above 80 percent maximum oxygen utilization (VO2 max) – allowing for very-high-intensity or long efforts with low calorie intake and also allowing for use of fat fuel stores during long steady-state exercise, even at a relatively fast pace (so much for the “fat burning zone” giving you the best bang for your buck). With high-fat, low-carb intake, you can go hard and still burn tons of fat. In addition, this means that more carbohydrate stores will be available when you really need them, such as for an all-out, 100%, maximum effort.
For patients who benefit, half achieve a seizure reduction within five days (if the diet starts with an initial fast of one to two days), three-quarters achieve a reduction within two weeks, and 90% achieve a reduction within 23 days. If the diet does not begin with a fast, the time for half of the patients to achieve an improvement is longer (two weeks), but the long-term seizure reduction rates are unaffected. Parents are encouraged to persist with the diet for at least three months before any final consideration is made regarding efficacy.
It usually takes three to four days for your body to go into ketosis because you have to use up your body's stores of glucose, i.e., sugar first, Keatley says. Any major diet change can give you some, uh, issues, and Keatley says he often sees patients who complain of IBS-like symptoms and feeling wiped out at the beginning of the diet. (The tiredness happens because you have less access to carbs, which give you quick energy, he explains.)