[tim-fan]

I believe in some conditions fat and/or protein can be used to restore glycogen via Gluconeogenesis https://en.wikipedia.org/wiki/Gluconeogenesis

I remember reading that for keto diets it's important to not eat too much protein, otherwise the excess protein may be converted to glucose, replenishing glycogen and knocking you out of ketosis.

[dawnerd]

From personal experience you’d have to eat a LOT of protein to kick you out. I do a pretty high protein keto diet and it works great. What really gets people is all the keto blogs talk about eating lots of fat. That great if you are doing keto for a lifestyle choice but if you’re doing it for weight loss you already have the fat and don’t need to boost your intake. Eating a fraction of the suggested macros still maintains satiety.

[Blackthorn]

Gluconeogenesis can't really turn fat into glucose, humans lack a key enzyme for that.

[arcticbull]

This is not accurate. If that were true people who fasted would die after about 3 days, but of course, the longest fast lasted about 350 days. The reality is after 3 days of fasting, your blood glucose level stabilizes. Your body must perform gluconeogenesis to survive because a few types of tissue require glucose to live - those without mitochondria. This means red blood cells and about 30% of the energy requirements of your brain.

Pathway is here if you're curious. [1]

[1] https://en.wikipedia.org/wiki/Gluconeogenesis