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Currently I eat some collagen bars for lunch, sometimes egg yolks, and then I have white rice and greens for dinner.

Hmm, only egg yolks, not together with egg Whites ?

And are these collagen bars something like this:
https://www.perfectketo.com/coconut-chocolate-collagen-bars/

???
Many thanks.

Ya just the yolks. Too much protein pulls you out of ketosis. All of the best nutrients are in the yolk anyway.

What I eat is very much like those bars. Here's the brand I use:
https://www.bulletproof.com/fudge-brownie-collagen-protein-bar-12-pack

Isn´t white rice not also hydrocarbons ?
Is Ketosis diet not about eating almost no hydrocarbons ?
But you are pretty slim, so it is probably no big problem for you, right ?

I'm doing cyclical ketosis. I go in and out everyday rather than every few days because it helps me keep weight on if I eat carbs before bed. So I'm in ketosis until dinner most days.