Let me start with a story: People are indeed paying more attention to a healthy diet nowadays. When eating at a buffet, many people will take less rice and add more sweet potatoes, corn, or even chestnuts, considering them coarse grains and thus healthier. You can also see stalls selling corn or sweet potatoes everywhere on the street, and buying one when hungry is a very effective way to curb your appetite. But the problem is, many people who eat these foods have no concept of "portion size," often treating them as snacks and eating as much as they can. In fact, although they are all low-fat, high-fiber foods, eating too much can still lead to weight gain.
Now, let's get to the reasoning: These staple foods are all carbohydrates, which are easily absorbed by the body and are quite high in calories. There's an easy-to-remember standard: a regular-sized 10cm sweet potato or one ear of corn has about the same calories as half a bowl of rice. Chestnuts have even more calories; two liang (100 grams) of chestnuts are equivalent to one bowl of rice. So, you must be very careful when eating them, especially those who treat them as snacks.
In summary, corn and sweet potatoes are more suitable as staple foods and provide a stronger sense of fullness. It should be noted that if consumed as a main meal, you should avoid eating other starchy foods to prevent weight gain.