Prior to the advent of exogenous insulin for the treatment of diabetes mellitus in the 1920's, the mainstay of therapy was dietary modification. Diet recommendations in that era were aimed at controlling glycemia (actually, glycosuria) and were dramatically different from current low-fat, high-carbohydrate dietary recommendations for patients with diabetes [1,2]. For example, the Dr. Elliot Joslin Diabetic Diet in 1923 consisted of "meats, poultry, game, fish, clear soups, gelatin, eggs, butter, olive oil, coffee, tea" and contained approximately 5% of energy from carbohydrates, 20% from protein, and 75% from fat [3]. A similar diet was advocated by Dr. Frederick Allen of the same era [4].
I do not think you are glad this diet was effective for this person. Your video recipe reviews are juvenile at best, and your overall review is extremely negative. My personal experience is wt loss of 60 lbs in 11 mos; three migraines in 11 mos vs minimum of three per month for over 53 years, and all I was trying to do by starting keto was delay type 2 genetic diabetes onset . I am no longer prediabetic and I have taken less sumatriptan in one year than I have historically taken in one month. I sincerely hope your review has not prevented one person from enjoying their life to the degree I have in the past 11 months as a direct result of the keto diet. Shame on you!
At the core of the classic keto diet is severely restricting intake of all or most foods with sugar and starch (carbohydrates). These foods are broken down into sugar (insulin and glucose) in our blood once we eat them, and if these levels become too high, extra calories are much more easily stored as body fat and results in unwanted weight gain. However, when glucose levels are cut off due to low-carb intake, the body starts to burn fat instead and produces ketones that can be measured in the blood (using urine strips, for example).