eli5: why is it so difficult to go a week without eating when we have 10s of thousands of calories worth of body fat?
In: 89
Because your fat reserves are *reserves*. That’s the last-ditch fuel your body burns to stave off starvation. In “normal” mode, your metabolism fuels your body mainly off your regular calorie intake.
The fat reserves take a different chemical/hormonal pathway (and extra water) to access the energy stored there.
This analogy’s not perfect, but retooling to a fat-based metabolism is a bit like trying to install and hook up a diesel generator *after* the regular power goes down. You can do it, but it’ll be damned inconvenient to everybody in the house until it’s up and going. No computers (brain no thinky so good on a carb deficit), regular lights don’t work, even if you can do a lot of day-to-day stuff by natural light or candle/lamplight…
Even once you make the switch and the lights are back on, you can have trouble with current regulation, and you definitely can’t run on backup power forever. Diesel exhaust is pretty toxic, for one thing, and eventually, your reserve fuel will just run out.
ETA: That kind of describes the issues people have when they try to switch to a keto diet – you basically stop taking in carbs until your body gets the message and retools to burn mainly fat instead.
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