If you really cut back on your carbohydrate intake you can move into a state of ketosis. In ketosis your body uses fat for fuel and turns some of this fat into what are called ketones. Ketones are an especially good energy source for the brain during periods of food scarcity, fasting and very low carbohydrate diets. As you can see from the above graphic, the younger you are the easier it is to get into ketosis.
This is one of several "What I Learned" videos that you can find on You Tube. They are all very good.
If you know of anyone who knows more about nutritional ketosis than Steve Phinney let me know. The book that he wrote with Jeff Volek - "The Art and Science of Low Carboydrate Living" - is a low carb high fat classic.
I referred to Jeff Volek above in my blurb about Steve Phinney. Here is a great presentation by Jeff on the subject of ketosis and keto-adaptation.
Babies are born keto adapted. Whether fasted for the first 24 hours of life or fed under normal nursery practices newborn infants have a degree of ketosis that is achieved by the adult only after 1-2 days of fasting.
Dom has been working on ketone science for over ten years.
In this short video Meryl Streep talks about a boy named Charlie whose epilepsy was cured by going on a ketogenic diet. Meryl Streep was also in a movie called "First Do No Harm" which is about a family that used a ketogenic diet to help a son that developed epilepsy.
The world famous Johns Hopkins Hospital has been using the ketogenic diet to treat epilepsy for almost 100 years.
Ben Bikman explains that you can stay in ketosis if you eat higher levels of protein. The effect of protein on insulin level depends your metabolic state. If you are already fat adapted and in ketosis then eating more protein does not kick you out of ketosis. However, if you are a beginner trying to get into ketosis you should moderate you protein intake until you become fat adapted.