We all like to joke about DG9J and what not, but honestly, although it defies belief, it isn't totally bullshit unbelievable. Xiao Feng's drinking ability, however, is.
In chapter 14, the chapter I am translating right now, the novel explicitly shows Xiao Feng drinking forty bowls of Chinese 'gaoliang' liquor, which is a form of hard liquor. It is also explicitly stated that each bowl contained half a 'jin', which means each bowl contained a quarter kilogram worth of alcohol. So the forty bowls of hard liquor which Xiao Feng drank, translates into TEN KILOGRAMS OF HARD LIQUOR. For us Americans, that's TWENTY TWO POUNDS of HARD LIQUOR.
Now, for the average human being, 7% of his body mass is blood. Xiao Feng is a huge, muscular guy, so let's say that he weighs 100 kg's, or around 220 pounds. This would give him roughly a total of 7 kg's worth of blood, ie roughly 15 lbs of blood in his body.
Meaning that Jinyong literally describes Xiao Feng imbibing much more alcohol than than he has blood!
Let's take this a step further. Ignoring the fact that it should be humanly impossible to take in that much liquid (people will easily die from even drinking that much water), let's calculate his blood alcohol toxicity. Jinyong describes them drinking 'gaoliang' alcohol, which is a VERY powerful and potent liquor, generally between 40% or 60% alcohol. For the benefit of the doubt, let's use the lower number, 40%. 40% of ten kilograms is 4 kilograms, so Xiao Feng literally has 4 kilograms worth of pure alcohol in his blood.
Now, for reference, a BAC of 0.5% (meaning 0.5 milligrams of alcohol for every 100 milligrams of blood) is fatal to almost anybody in real life, although serious alcoholics have been known to go as high as as a BAC of 0.9%.
Again, ignoring the fact that it's impossible to add so much fluid into a person's body, Xiao Feng, after drinking what he did with Duan Yu, will literally have 17 kg's worth of fluid in his system, 4 of which is alcohol. That gives him a blood alcohol level of 25%, or a BAC of 25 (meaning, 25 milligrams of alcohol for every 100 milligrams of blood).
That is @%@$#$ insane.
What's even more insane is that not only is he totally sober, he doesn't go to the bathroom. He goes and gets into a JOGGING COMPETITION with Duan Yu.
*facepalm*