So first off I’d like to change my description of a Ketogenic diet. I have been referring to it as “The Nuclear Option” since it’s sort of a last-ditch final effort to lose weight. Over on a reddit thread there was a great write up about how when you force your body into ketosis, you are deliberately creating a (non-fatal) deficiency in a (mostly) essential nutrient: carbohydrates (glucose). Yep, that’s exactly it. Our bodies have the ability to run on carbohydrates, amino acids and fatty acids; essentially we’ll take anything we can get so as to not starve.
Ultimately any time you lose weight it simply comes down to your body using/burning more energy than you recently consumed so it’s forced to use reserves. You have some glucose reserves in your liver and muscles, protein that can be broken down into glucose in your liver; and you have fat. Some cells burn fat just fine, most would rather use glucose. Traditional weight loss (just less calories) works because as you have a calorie deficit, your body will eventually convert stored fat into energy. Some will be made into glucose via Gluconeogenesis, some will be made into ketone “bodies”. Specifically forcing your body into a state where it is mostly doing the ketones is the cheat.