A peasants diet...healthy?
Honestly, I don't know much about the diet of the dark ages, though something tells me it was healthier. In feudal middle ages, a peasant could not hunt, as forests were the property of your feudal lord. Hunting would be poaching, and punishable by death. Fish was a luxury inland, and I wager coastal peasants did not see much of it either. They ate grain soup or onion soup day in and day out, possibly some fruit, yeah. Still not nutritious enough.
It's highly possible that they ate better in the dark ages, though there are more factors to consider. As for the nobility getting fat? Nah. Not Dark Ages.
And yes, I definitely agree. It's pretty hilarious and made me chuckle in surprise the first time I saw it.