Well, to be fair, Leptin wasn’t even discovered when he wrote his first book in 1972. He would, however, have known about insulin, which is in any case, the “master hormone”.
People got very excited about leptin for a while, but in the end, we can’t do much about it directly.
We can do something about insulin, however.
True
But we can do something about leptin…
Insulin has direct knock on effects for both leptin and gherlin.
Fix the insulin, and you are on your way to fixing the other two. 
To answer your question non alcoholic fatty liver is associated with over consumption of carbs. There have been numerous anecdotal accounts (believe them or not) of people having their liver enzymes improve and return to normal on keto or LC.
One thing keto has tuned me into is the protruding liver most middle aged people have. Even thin people will have a bulge above their waist in the middle. While mine is not perfect, about 2 months into keto I noticed that this bulge went away mostly. I am not a big blood tester so I have nothing to back up.
I agree that we have a bias just as the vegans and low fat camp have a bias but my liver is not something I worry about on keto. I am sure there is plenty to critize in keto studies if you look hard enough. Plus Atkins did not have an autopsy the way Pritikin did.
So I do wonder but as the months have gone by, I wonder less. I am not sure why, confirmation bias? I have no idea
The fortunate thing is that both insulin and leptin resistance are dealt with at the same time by becoming lipolytic. Once the glucagon secretion pattern is established, resistance of both hormones falls.
When following a restrictive diet along macros of the NAD, people are subject to the one-two punch of both ghrelin secretion (hunger) and orexigenic hormone resistance withdrawal. These two things together eventually sabotage most Carb based diet efforts.
I’m 8 months into keto and appreciating the concept of insulin resistance more & more each day.
Inexplicably, that picture of an insulin molecule in @richard 's post is the first time I’ve seen how ginormous/complex the insulin molecule is relative to glucose.
Is there a diagram/photo section of the forum for such images to be aggregated? Before and after photos of ketopians are geat, but that image of insulin made me feel like Ahab staring at a certain white whale.