For the body, energy is life. The four organs that demand the most energy to operate, pound for pound, are the brain, heart, liver, and kidneys (muscles are fifth). Restricting the energy supply to any of these reduces not only their ability to function properly but also the ability of all of the parts of your body that depend on them—which is pretty much everything that keeps you alive.
To avoid that danger, your body has multiple methods of providing energy. The first line of defense is the fuel called glucose, also called blood sugar, which works just fine as a fuel for every part of your body. Glucose can come directly from the digestion of carbohydrates, and it can be stored between meals energy in a form called glycogen. [1] When carbohydrates aren’t provided, and glycogen is running low, the body can make glucose from proteins and a substance called glycerol (which is found in fat molecules).
But glucose isn’t the only fuel your body can use. Muscles and many other types of cells in the body can also burn fat for energy, and in general your body uses both glucose and fat in varying amounts, depending on what’s most available. That said, some parts of the body cannot utilize fat as fuel—including the brain, and red blood cells—which makes the maintenance of healthy glucose levels an extremely high priority.
Which brings us to keto, and what it really means. On a low carbohydrate, high fat diet, your body can be hard-pressed to maintain blood sugar levels, even by making its own glucose from protein and glycerol. To maintain a minimum blood sugar level, it turns more and more to fat as fuel. And your liver (the chemical factory of your body) has another trick up its sleeve: converting some of that fat to a kind of molecule called ketones. These ketones are a third kind of fuel, and what’s even better, they’re a kind of fuel that the brain can use to supplement glucose. Ketones can also be used as fuel in other parts of the body. [2]
This production of ketones is called ketogenesis (keto = ketones, genesis = create). And the word “keto” is really a short form of the phrase “ketogenic diet.”
Your liver generates ketones every night, as one of your body’s tactics to maintain glucose levels by using alternative fuels whenever carbohydrates aren’t being digested and glycogen is running low. When you’re on a low carbohydrate, high fat diet, the amount of ketones being generated increases to a level that is usually described as a state of ketosis (keto = ketones, osis = a condition).
You should also know that too high a concentration of ketone molecules can be toxic, a condition called ketoacidosis. This is most often seen in unmanaged diabetes, alcoholism (which affects the liver), and severe starvation.
Does restriction of dietary carbohydrates to create the condition of ketosis make you healthier? You’ll find medical professionals, nutritionists, and diet gurus on both sides of that question. But if you understand the above, you’ll be in a much better position to follow the arguments.
References
1. Glucose can also be converted to fat for energy storage, which generally occurs once there’s no more space for glycogen. The amount of energy per unit weight of fat is roughly 6 times higher than for glycogen.
(https://www.ncbi.nlm.nih.gov/books/NBK22369/).
2. Biochemistry, Ketogenesis, Kiranjit K. Dhillon; Sonu Gupta, National Center for Biotechnology Information. (https://www.ncbi.nlm.nih.gov/books/NBK493179/)
