I went through a medically supervised keto diet program back in the 90's, and in combination with exercise, went from 260 lbs down to 180 lbs in about 10 weeks. So, does it work? Absolutely. Is there anything magic about it? No. Popularized by Atkins, these diets demonize carbs. About 40% of the American diet is made up of carbs. Cut out 40% of the calories in your diet - I don't give a shit if it's proteins, carbs, or fat - you will lose weight. One promise of the diet was that once you entered ketosis, magically, hunger would cease to be an issue, and the diet would be painless. That was total BS. It worked, but it was no less painful than any other calorie restricted diet.