Bun cha sits at 500 calories for a standard set, and the split is roughly half noodles, half pork. The 200g plate of bun is 220 calories on its own. The pork is where the fat is: a normal quan gives you two or three patties of minced pork shoulder plus three or four slices of grilled belly, 100g in total and about 230 calories because belly is 30 percent fat and the patties are mixed with fat too.
The dipping bowl looks innocent because it is mostly liquid, but it is fish sauce, water, vinegar and around 10g of sugar, so 40 calories before you count the pork fat that drips into it off the grill. Most people drink or spoon the whole thing. The green papaya and carrot slices in it are the only free part.
The real number for most people is not 500. It is 640 to 780, because nem cua be (the square fried crab spring roll) is 140 calories each and quan sell them in pairs. A set with two nem and a second plate of bun, which the owner will bring without asking at a busy place, is over 850 calories for one lunch.