The “keto” in a ketogenic diet comes from the fact that it makes the body produce small fuel molecules called “ketones”.
This is an alternative fuel for the body, used when blood sugar (glucose) is in short supply.
Ketones are produced if you eat very few carbs (that are quickly broken down into blood sugar) and only moderate amounts of protein (excess protein can also be converted to blood sugar).
Ketones are produced in the liver, from fat. They are then used as fuel throughout the body, including the brain. The brain is a hungry organ that consumes lots of energy every day,
and it can’t run on fat directly. It can only run on glucose… or ketones.
On a ketogenic diet your entire body switches its fuel supply to run almost entirely on fat. Insulin levels become very low and fat burning increases dramatically. It becomes easy to access your fat stores to burn them off. This is obviously great if you’re trying to lose weight, but there are also other less obvious benefits, like for example less hunger and a steady supply of energy.
When the body produces ketones it’s said to be in ketosis. The fastest way to get there is by fasting – not eating anything – but obviously it’s not possible to fast forever.
A ketogenic diet, on the other hand, can be eaten indefinitely and also results in ketosis. It has many of the benefits of fasting – including weight loss – without having to fast.