During the 1920s and 1930s, when the only anticonvulsant drugs were the sedative bromides (discovered 1857) and phenobarbital (1912), the ketogenic diet was widely used and studied. This changed in 1938 when H. Houston Merritt, Jr. and Tracy Putnam discovered phenytoin (Dilantin), and the focus of research shifted to discovering new drugs. With the introduction of sodium valproate in the 1970s, drugs were available to neurologists that were effective across a broad range of epileptic syndromes and seizure types. The use of the ketogenic diet, by this time restricted to difficult cases such as Lennox–Gastaut syndrome, declined further.[10]

A computer program such as KetoCalculator may be used to help generate recipes.[47] The meals often have four components: heavy whipping cream, a protein-rich food (typically meat), a fruit or vegetable and a fat such as butter, vegetable oil, or mayonnaise. Only low-carbohydrate fruits and vegetables are allowed, which excludes bananas, potatoes, peas, and corn. Suitable fruits are divided into two groups based on the amount of carbohydrate they contain, and vegetables are similarly divided into two groups. Foods within each of these four groups may be freely substituted to allow for variation without needing to recalculate portion sizes. For example, cooked broccoli, Brussels sprouts, cauliflower, and green beans are all equivalent. Fresh, canned, or frozen foods are equivalent, but raw and cooked vegetables differ, and processed foods are an additional complication. Parents are required to be precise when measuring food quantities on an electronic scale accurate to 1 g. The child must eat the whole meal and cannot have extra portions; any snacks must be incorporated into the meal plan. A small amount of MCT oil may be used to help with constipation or to increase ketosis.[37]
When you eat less than 50 grams of carbs a day, your body eventually runs out of fuel (blood sugar) it can use quickly. This typically takes 3 to 4 days. Then you’ll start to break down protein and fat for energy, which can make you lose weight. This is called ketosis. It's important to note that the ketogenic diet is a short term diet that's focussed on weight loss rather than the pursuit of health benefits. 
In many developing countries, the ketogenic diet is expensive because dairy fats and meat are more expensive than grain, fruit and vegetables. The modified Atkins diet has been proposed as a lower-cost alternative for those countries; the slightly more expensive food bill can be offset by a reduction in pharmaceutical costs if the diet is successful. The modified Atkins diet is less complex to explain and prepare and requires less support from a dietitian.[55]
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]
“Combining a super restrictive diet with long periods of non-eating is not good,” says Keatley. “The body will cannibalize its own muscle for energy if intake from food is too low but the body does not differentiate between something like a calf muscle or a heart muscle. Keep in mind all your important organs are made of smooth muscle and going on a diet like this may harm something like your bladder or lungs just as much as provide fat loss.”
The ketogenic diet is usually initiated in combination with the patient's existing anticonvulsant regimen, though patients may be weaned off anticonvulsants if the diet is successful. Some evidence of synergistic benefits is seen when the diet is combined with the vagus nerve stimulator or with the drug zonisamide, and that the diet may be less successful in children receiving phenobarbital.[18]
Together, glycogen loss and low insulin levels can cause us to excrete so much water and sodium that we experience some of the most common keto flu symptoms, such as dizziness, nausea, cramping, headaches, and gastrointestinal issues. Fortunately, these symptoms can be avoided by drinking plenty of water and supplementing with the right minerals (more on this later).

Note that the term “reversal” in this context simply means that the disease gets better, improving glucose control and reducing the need for medications. In the best case, it can be so much improved that blood glucose returns to normal without medication, long term. In this context, reversal means the opposite of the disease progressing or getting worse.