The beef is not the problem. A cha chaan teng gives you about 70g of sliced beef, roughly 120 calories and 18g of protein. The instant noodles are the problem: one cake of 公仔麵 or 出前一丁 is deep fried at the factory and carries about 470 calories and 18g of fat before it touches water. That is the same as a bo lo yau and a half, sitting at the bottom of your breakfast bowl.
Satay sauce is the second hit. Hong Kong satay sauce is peanut, dried shrimp, shallot and a lot of oil. The kitchen fries the beef in it, then spoons more over the noodles, so you get around 80 calories of sauce and most of it is fat. One dietitian who ranked cha chaan teng items said satay beef noodles should be a once a week thing at most, and at 667 calories with about 1,300mg sodium, that is reasonable advice.
This is a breakfast, remember. 670 calories at 8am, with a milk tea (110) and the buttered toast that comes in the set (250), is over 1,000 calories before you sit down at work. For most people trying to lose weight, that is half the day gone. The same beef on rice vermicelli in clear soup would be about 350.