Speaking of the history of fasting… this is exactly what led to the introduction of what’s known today as the ketogenic diet.
This high-fat, very low-carbohydrate diet mimics human fasting metabolism and was used medically in the early 1900s to manage epileptic seizures5 as well as Type 1 diabetes6 before the advent of insulin.
Keto is a way of eating that restricts carbohydrates to the point that our body needs to vet out an alternative fuel source to feed our glucose-hungry brain. (Unlike most of our tissues, the brain cannot burn fats for fuel.) That’s where ketones come in.
When we lower carbohydrate intake, and by virtue, blood sugar and insulin levels, to the point that puts the brain at risk of an energy deficit, the liver starts converting fats (either from our diet or body fat stores if in a caloric deficit) into ketones.
This is what defines a keto diet: an elevation of ketones. It turns out that the brain loves ketones so much that it uses them even in the face of impaired energy metabolism. Ketones do a lot of other extraordinary things in the body that scientists are still unpacking.
It also shows promise for promoting brain health and treating mental health conditions10. “A ketogenic diet is a really important tool for people who are trying to improve their brain’s access to energy and the overall health of their brain’s metabolism,” nutritional psychiatrist Georgia Ede, M.D. says on the mindbodygreen podcast.