Again fucking Insanity you do realize 2-3k calories a day is what is recommended for an adult male. Who the fuck is telling you that you can live off 850 calories a day?
Where are you getting this horseshit?
Health Canada.
You don't NEED 2-3K calories daily.
You only NEED 850 well-selected calories to maintain optimal health.
Though that requires excellent food selection.
I was eating 1,000 to 1,100 calories daily for the past eight years. But I was clearly deprived in iodine, or something else that I needed for optimal thyroid health.
I'm not talking about what the food companies want us to eat. I'm simply saying:
We only need 850 calories, properly selected, to maintain optimal health.
If we're talking just SURVIVAL, you could probably go as low as 300 calories - but don't quote me on that.
You're talking about recommendations for living in Western society. I'm talking about merely maintaining optimal health.
You do NOT need 2-3K calories for that. Arguably, caloric deficits are much healthier.
The #1 environmental factor that people who live to age 110+ have in common is caloric restriction.