The 450 calories in a bowl of pho splits about like this: 200g of cooked banh pho noodles is 220, the 80g of beef is 160, and 300ml of broth is only 50 even with the fat floating on top. The herbs, onion and bean sprouts add maybe 10. So half the bowl is noodles. That is the part to control if you want to eat pho five mornings a week without gaining weight.
The beef cut changes the number more than people expect. Tai (rare sliced round) is lean, about 130 calories per 80g. Nam (flank) and gau (fatty brisket) run 200 to 230 for the same weight. A bowl of tai nam gau with a spoon of the rendered fat from the pot is closer to 600. The quay, those fried dough sticks, are 120 to 150 each and most people eat two.
Pho is one of the better street breakfasts if you order it plain. You get 28g of protein, the broth fills you up with almost nothing, and there is no oil beyond what is on the beef. The problem is a 60,000 dong bowl at a busy quan is often 250g of noodles, not 200, and the free refill of broth comes with more fat skimmed from the pot.