So it's true! It's this one brief mention in the papal letter that made future historians label Lestek as a lazy, obese drunk. Especially that "having changed habit into nature" sounds very much like a nice euphemism for "being an alcoholic". But there's a few things here that don't look right…
First of all, what kind of alcoholism makes you drink beer and mead, but stay away from wine? Secondly, how come the pope bought an excuse so flimsy? And does "''corporis gravedine gravis'' " really mean "heavy in his body"? This Latin fragment could be also translated as "being full of catarrh" or "suffering from a heavy cold". Anyway, I suspect that Lestek was trying to excuse his failure to join the crusade with some grave illness, and the necessity to replace wine and water in his diet with beer and mead was not necessarily his personal preference, but a medical prescription. Yes, I know, neither a cold nor being overweight would let me get away with not showing up to work, but perhaps medieval attitudes to sick leaves were more relaxed?
It's also possible that the pope was simply being sarcastic. What he meant was perhaps something like, "look at this northern brute who promised to go on a crusade, but now says he doesn't feel like it! The fat drunken sloth who probably can't even live without those barbaric northern drinks like beer and mead!" But if this was the case, then what convinced the pope to forgive Lestek and not excommunicate him after all? Well, what could have worked was what the duke offered as a replacement.