as my name says I'm a cyclist
on long trips we need to take sugars to replenish our fast energy
there are 2 tresholds in the heart rate, which is different for each individual
only below the lowest treshold fat can be burned, above the highest you use some 'nuclear non oxygen' fuel stored in the muscles and once that is depleted you start consuming your own muscles, between the two tresholds both carbohydrates and sugars can be consumed
so if you're on an exclusif fat diet, can you go beyond the lowest treshold, i.e., can you do intense physical efforts?
do triathletes have a different diet on training then on competition days?
that is because you are carb/sugar adapted, your body starts using protein from muscles, because protein can be transformed into glucose.
Your body prefers sugars over fat, so you are working as sugar burner.
Thing with ketosis is once your body starts to produce ketones from fat, it loses its need for sugars, and thus not waste muscle. Also the reason for not including lots of protein on ketogenic diet, especially during adaptation period, because its a trap in a sense, your body will try to convert protein into glucose rather then using fat, but MCT fats like coconut oil can help to mitigate that
There is a period of adaptation, think of it this way, with modern/farmer diet your body was accustomed to glucose basically from birth. There is a thing called keto flu, which is a adaptation period that can last from a weak to a month, depending on a person, and in that time people can experience nausea, insomnia, sweating and so on, because thats the breaking stage, almost like coming of the drugs. In that period its advisable not to stress body, eat lots of minerals, salt, and drink water, because you can lose water as carbohydrates hold water as their name suggest.
I was introduced into Ketogenic diet, because i stumbled upon research for Navy SEALs diet that would allow them to keep focus and energy during long periods of combat, then athletes started using it as well, usually endurance, triathlon, swimming, marathon, cycling.
Also those adopted to fat in sports, still can use carbs-drinks as refreshment, but they need way less of it, and your recovery is much better, you can cycle 40km up hill, and still go running tomorrow
If you are interested, you can search youtube for ketogenic diet in sports, there are lots of videos on the subject