Of the 12 cha chaan teng dishes in the HK01 dietitian ranking, tomato beef macaroni came in at 368 calories, sixth from the top and less than half of the luncheon meat instant noodles (785) that most people at the next table are eating. The macaroni is boiled, the beef is sliced lean flank, and the soup is tomato, ketchup and stock. There is nothing fried in the bowl unless you add a fried egg, which is another 100.
The same ingredients on a rice plate are a different story. 鮮茄牛肉飯 with a reduced portion of rice is 665 calories in a Weekend Weekly dietitian list, and a full rice portion pushes it over 750. Rice is denser than macaroni in soup, and the plate version uses more oil to stir fry the beef and tomato. So if you want the tomato beef flavour, the noodle soup gets you there for about 300 fewer calories.
Where it goes wrong is the sugar and salt in the soup. Cha chaan teng tomato broth leans on ketchup, and a bowl can hold 15 to 20g of sugar plus 1,500mg or more of sodium. Drinking every drop is what tips this from a light lunch into a sweet, salty one. Eat the macaroni and beef, take a few spoons of the soup, and the number stays near 320.