A short YouTube monologue explaining why reintroducing carbohydrates ends ketosis: the body preferentially uses glucose, so raising blood glucose and insulin halts fat burning. The speaker warns that consuming high dietary fat while glucose/insulin are elevated leads to increased circulating triglycerides and VLDL (dangerous cholesterols), and frames keto as a long-term commitment (“the diet you marry, you don't date”).
Chapters
Why can't you cheat on a keto diet? Because once you become fat adapted, as soon as you put carbohydrate, high carbohydrate back into the body, then it instantly will stop processing fat. And you're eating a high fat diet. And so now the fat will build up in the blood and it will be stored in the visceral tissue rather than being used as an energy source. Remember, the first preferred source of energy for the body, and there are no exceptions to this rule, is always glucose. So if you have sugar in your blood, you have no choice. Your body will always, always choose that source for energy first. So you have to bring the glucose down in order to get into ketosis. So as soon as you raise your blood sugar, raise your glucose and you raise your insulin. Now your body can't burn fat, but you have high amounts of fat in your diet now you're in a dangerous situation. Your triglycerides skyrocket. You'll see that your dangerous cholesterols, your VLDL cholesterols will skyrocket. Keto diet is just like you said, the diet that you marry, you don't date.