I sometimes fast instead of eating when I travel, but I usually don't go more than 16 hours between meals. Cristi Vlad, a ketogenic diet enthusiast, describes what it is like to go 44 hours without eating. As you can see from his Ketostix (photo above) he is burning a lot of ketones.
Whenever I fly inter-continentally I fast; that is - I don't eat. I benefit from this by avoiding spending money on airport food and by avoiding airplane food.
Thus, I have no stomach upset. My GI tract is in 'reverie' mode, unlike when I was eating during my long travels. Back then, my stomach was somewhat disturbed and I had trouble recovering from jet lag, which is inexistent with this current strategy. I am aware, though, that correlation is not causation and that other factors from my life could contribute to this. Anyhow...
