Updated: Jun 14
It takes 3 days of low carbohydrate fasting to reach ketogenesis.
Acute cold exposure can get you there immediately.
Why do people say keto can be dangerous?
My first experience with ketosis was in December 2001, when my 6 year old son was diagnosed with Type 1 diabetes. I knew nothing about metabolism, about blood glucose, about insulin, about free fatty acids, and I had never heard of plasma ketones.
My ignorance almost killed my son.
Type 1 diabetes (T1D), also called juvenile diabetes, is an autoimmune disorder that causes the body to destroy the islet cells in the pancreas that produce insulin. No one knows why the body attacks itself, although it is now understood that Vitamin D deficiency in the first year of childhood is a significant risk factor for later development of T1D.
Because my son was born in October in northern New York where there was precious little sunlight, it stands to reason that he was Vitamin D deficient the first six months of his life.
Six years later, when he was admitted to the hospital with full-on T1D, his blood sugar was over 700 mg/dL (about seven times a healthy level). Without insulin to carry glucose from his bloodstream into the cells of his body where it could metabolized for energy or converted into white fat, the only mechanism for clearing glucose from his body was thru his urine.
And he couldn't pee fast enough to rid his body of the sugar in the fruit juice I was feeding him. I thought he had the flu, and that the Vitamin C in orange juice would do him some good.
I was wrong.
But it wasn't necessarily the fruit juice that was about to kill him. More serious was the fact that his body, in a desperate attempt to keep his glucose-starved cells alive, was producing massive levels of ketones.
In his new book, Ketones, the 4th Fuel (2020) science journalist Travis Cristofferson describes how the body obtains energy from four different types of food: 1) carbohydrates, 2) fats, 3) protein, and 4) ketones.
The first three types of food are abundant. Carbohydrates include simple sugars (e.g., fruit juice) and more complex grains, fats and protein are found in meat, fish, nuts, and some seeds, but ketones are unusual in a normal diet. Some biohackers consume coconut oil, or medium-chain triglycerides (MCT) to boost their ketone levels, but for the most part ketones are only in the bloodstream when they are synthesized in the liver to provide fuel when glucose is scarce.
In people without T1D, a low carbohydrate diet will cause white fat cells to release free fatty acids into the bloodstream, where they are converted to ketones in the liver, and transported back through the bloodstream to muscle and other cells for the rapid conversion into energy. That's why a ketogenic diet is so effective for fat loss. Switching your metabolism into ketosis will cause the white fat cells in your body to shrink, resulting in a leaner body composition.
Ordinarily, healthy blood glucose levels are maintained during ketosis -- even on zero carbohydrate diet -- by a process called gluconeogenesis, in which the liver (and kidney) form blood glucose from non-carbohydrate sources (Berg et al, 2002). However, in my son's case, glucose was abundant in the bloodstream but unavailable inside his cells, because he was not making enough insulin to carry the glucose from his blood across his cell walls.
To compensate for the lack of energy inside each cell, his liver was working overtime to produce more and more ketones -- so many that the concentration of ketones began to lower the pH of his blood to a life-threatening condition called ketoacidosis.