Some people may wonder why the girl in the same office suddenly stopped dining with them; others may be curious about what's inside the boxes that people carry in the early morning subway.
A national survey led by China Youth Daily earlier this month showed that over 70 percent of the 2,284 questioned were aware of Daifanzu and 18 percent admitted to being one.
Concerns such as rising prices and food safety have prompted many office workers in big cities to safeguard the quality of their meal as well as the money in their pocket.
Bring your own food
New graduate Yang Yang just found a job working for a website in Beijing.
"There are less and less options for a reasonable lunch around the office, especially one under 10 yuan ($1.5). I started to make my own food as soon as I started work; now I do it every workday," she said.
Although the editor with an international publication making good money, 27-year-old Laura Zhou also chooses to be a Daifanzu so that she can enjoy her own food in the office.
She was aware of rising prices but what worried her most were the frequent reports concerning food safety, from illegally recycled cooking oil to contaminated vegetables.
And joining the Daifanzu is not just for girls; 26-year-old business consultant Si Zeyang makes lunch for himself, whenever he finds time.
"It is so important to eat healthy, and making my own food can do that," he said. "I recommend all office workers make their own lunch if time allows," he added. "If I have the time, I would like to cook and take my lunch [in] every day."
Expertise for better food
"The best way is to find the balance among a wide arrangement of foods such as meat, grain, vegetable and so on," Zhou Jian, a nutrition professor with the Beijing University of Chinese Medicine said.
Over-use of oil and sodium should be avoided, she added.
Canadian nutritionist Dolores Chung, director of the Hong Kong based Dynamic Health Centre, has some more detailed advice.
She says it is always important to use seasonable food. "I know big cabbages in winter are good in Beijing, some curried or spicy chicken, or mutton with rice, would be good for winter-eating too, with sauces to go with rice."
Fruits and salads are most healthy as they don't require reheating and maintain nutrition.
Thermal containers, which can keep food warm for a few hours, are recommended to avoid losing nutritional value in the microwave.
"Just reheat for less than one minute or so… the vitamin C should still be kept," she said. "Always use a plastic lid, not fully covered, to keep the water in the food. Heavy meat should be avoided… better eat some foods which are easy to digest."